UC-NRLF $B 3D3 DMT AGRICULTURE BY R. HEDGER WALLACE n LATE LECTURER AND EXAMINER IN AGRICULTURE TO THE EDUCATION DEPARTMENT OF VICTORIA AND THE VICTORIAN DEPARTMENT OF AGRICULTURE IX.X.XJSTRi^TE3:> LONDON : 38 Solio Square, W. W. & R. CHAMBERS, Limited EDINBURGH : 339 High Street r ;• Edinburgh : Printed by W. & R. Chanibers, Limited o PREFACE. This book has "been written with the object of placing before the student and reader a simple statement of the Principles of Agriculture, based on general practice, and not restricted to any specified country, or adapted to special clinjatic or other conditions. The book has been prepared on the lines of the new official syllabus of ' The Principles of Agriculture' issued by the ^Department of Science and Art of the Committee of Council on Education,' and will be found to meet the requirements of the Pirst Stage, or elementary course. At the same time, particular care has been taken to make it useful and serviceable as a manual or text-book in any of the colonies, since the natural laws on which agricultural principles are founded are of universal application. The general reader must bear in mind that the book deals with elementary subjects only, and, for the greater part, on the lines Avhicli the official syllabus lays down as suitable for an elementary course of instruction. But tliis syllabus has not been slavishly followed, and in many of tlie sections, especially in that on tillage and crops, subjects liave been discussed which should be placed before all students of elementary Agriculture. Students preparing for the Science and Art Examination may also consult Pro- fessor Warington's Diagrams of the Principles of Agri- mtltare. AVlien used as a class-book, the teacher should illustrate his lessons by exhibiting the objects spoken of, by perform- PREFACE. ing experiments, and by showing dingninis or drawings. The teaching shonld he made as practical and attractive as possible, and examples should be chosen by preference from local objects and practices. The class should also be well exercised in questions bearing on the subject under discussion. The illustrations have been made a special feature, and I am indebted to the courtesy and kindness of the various firms named in the context for being able to add such an attractive auxiliary to the text. It has been my endeavour to avoid errors, as far as possible, by seeking the advice and assistance of acknow- ledged agricultural experts and scientific farmers, and I beg to tender my sincere thanks to all who have so kindly advised and assisted me. My special thanks are due to Mr John Speir, of ISTewton Farm, Newton, Glasgow, for reading my proofs and favouring me both with valu- able suggestions and practical corrections. In preparing this book, I have consulted many authorities, specially the works written or edited by Messrs Aikman, Fream, Macdonald, Scott, and Warington. I have also made free use of notes taken, when a student, of the late Professor Wilson's lectures at Edinburgh University. This work will be found, I trust, to be based on the facts of modern agricultural practice and the results of scientific agricultural investigations, and that it will give the teacher, student, and general reader a fair elementary idea of the subject. R. HEDGER WALLACE. CONTENTS. CHAPTER p^gg I. Introd action 7 II. The Natural Kingdoms 9 III. Forms of Matter 12 IV. Atmospheric Air l(j V. A tmospheric Air — contimiecL 20 VI. Water 24 VII. Metals 28 VIII. Non-Metals 32 IX. Oxides and Salts, Acids and Alkalies 35 X. Carbon Compounds 37 XI. The Ash and Volatile Portion of Plants 40 XII. Soil-Food of Plants 46 XIII. Seed — Germination 49 XIV. Growth— Othce of Leaves 55 XV. Growth — Sap Movements 63 XVI. Blossoms and their Functions 67 XVII. Farm-Seeds 70 XVIII. What are Soils? 75 XIX. Lava and Peat Soils 77 XX. Humusand Stones 81 XXI. Properties of Soils 85 XXII. Conditions of Fertility 92 XXIII. Classification of Soils ■.. 95 XXIV. Some Constituents of Soils 100 XXV. Soil Physics 104 XXVI. What Frost, Water, and Air do to Rocks 112 XXVII. Removed Soils 115 XXVIII. Formation of Surface Soil and Subsoil 118 XXIX. Soil Chemistry 123 XXX. Soil C\\em\^tvy— continued. 1 29 XXXI. Cultivation— A Means of Enriching Land 137 XXXII. Cultivation — A Means of Cleaning the Land 141 XXXIII. Cultivation— A Preparation for Seed 143 XXXiv, Cultivation— An Aid to Root Development 148 CONTENTS. CHAPTKR PACE X XX V. ■ Ti 1 1 age 1 54 XXXVI. Implements for Working Soils— Ploughs 160 XXXVII. Implements for Working Soils — Cultivators, Harrows, &c 1 73 XXXVIII. Implements for Sowing Seed 179 XXXIX. Implements for Interculture 187 XL. Exhaustion and Improvement of Soils 191 XLI. Claying and Sanding, Paring and Burning, Marl- ing, Warping, &c 197 XLII. Drainage 201 XLiii. Drainage Systems and Methods 206 XLI V. Irrigation 21 ,3 XLV. Manure 222 XLVI. The Character and Preparation of Farmyard Manure 226 XL VII. Composition and Effect of Farmy.ard Manure 236 XLVIII. Food in Kelation to Manure 239 , XLIX. Other General Manures 244 L. Phosphatic Manures 249 LI. Nitrogenous Manures 259 Lii. Potash and other Manures 262 LIIL Lime , 265 LI V. Rotation of Crops 273 LV. Rotation for a Light Soil 278 LVI. Rotation for a Clay Soil 282 LVII. Rotation for Loams 285 LVIII. Distinctive Characteristics of Crops 291 Lix. Wheat and Rye 296 LX. Barley 300 LXi. Oats 303 LXIL Meadow-Grass and Meadow-Hay 306 LXllL Grass Seeds 309 LXiv. Beans and Peas 318 LXV. Leguminous Fodder Crops — Vetches, Clovers, Sainfoin, and Lucerne 320 LXVl. Other Fodder Crops 323 LXVii. Root-Crops —Man gel- Wurzel, Turnip 326 LXVIIL Root-Crops— Swede, Potato 332 LXIX. Harvesting and other Machinery 336 LXX. Conclusion 345 — -=^ or\r:iR W^ '^^%^ Jlf.TiH.i'iiT,^ ,^ PRINCIPLES OF AGRICULTURE. CHAPTER I. INTRODUCTION. 1. The word Agriculture means 'field tillage;' and it comprises all the different kinds of work that a farmer has to do. In talking about field culture, we must first describe the materials with which the farmer works in order that he may produce food for man and beast. They are the soil, seed, and manure. Besides these, water, air, and sunshine are necessary ; but these are not under his control as the others are. The farmer can only begin his work, for when he has prepared the ground, and sown the seed, he must depend upon ]N"ature to make the seed grow, and produce the fruit, ripe for use. 2. The first object of agriculture is the production of crops, the second being the breeding and feeding of animals ; and Agriculture is both an art and a science. The art of agriculture is so to manage land anywhere as to obtain profitable returns in crops and live-stock ; for practices and procedures in difterent countries will vary. The science of agriculture is a knowledge of the fixed principles which underlie the art, and exj^lain and reconcile differences in practice and procedure. The real work of 8 PRINCIPLES OF AGRICULTURE. agriculture begins witli actual practice on the farm, so that while studying first principles we must not forget tliat an important part of agriculture can only be taught and learned on a farm. Agriculture is a subject of vast importance and comprehensiveness, as in distribution it is nearly equal to our dry ground, and includes the growing and rearing of all the plants and animals requisite for the well-being of man. It includes not only the cultivation of wlieat, barley, oats, turnips, and potatoes, but maize, millet and rice, vines, tobacco, and tea. It is a serious mistake to suppose that a knowledge of the principles on which European agriculture is founded is of little value elsewhere. The process of plant cultivation and the treat- ment of live-stock may materially differ in two countries, yet the basis of the industry remains the same, for the principles of agriculture are simply natural laws. The butter made in Australia is identical with that made in England, and the composition of water in America is the same as water in Africa. 3. We know there are many different kinds of soils, and some will produce certain crops much better than they will others ; so the farmer must understand the different kinds of soils, and for what crops they are best suited. In this book will be described the various plants, soils, and manures, and how the farmer uses them in order to produce the largest crops. 4. Plants require food both from the soil and the air: and the food which they get from the soil includes many different substances. We should know something about these substances, in order that we may the better under- stand the composition of plants, of animals, of soils, of manures, and of the air. The science or study which teaches us about the composition of all these things is called Chemistry. 5. Plant development consists in the absorption and INTRODUCTION. 9 re-arrange meut of substances that previously were in the soil or air. This re-arrangement causes a disappearance of the former properties of these substances, arid gives rise to new characters, and is a chemical change. There are about fourteen of tliese substances of special interest to the farmer, as they are found in considerable quantities in plants, soils, and animals. Hydrogen H Oxygen O Nitrogen . . N Chlorine CI Phosphorus P Sulphur S Carbon C Silicon Si Calcium Ca Potassium K Sodium Na Magnesium Mg Aluminium Al Iron Fe These substances, we nmst remember, are the agricultural elements, and the symbols given are known to chemists in all parts of the world, and universally employed. Questions.— 1. What are the objects of agriculture, and what does the word mean ? 2. With what materials does a farmer work, and are they all under his control? 3. Name the tliree subjects studied under principles of agriculture. 4. Are the principles of agriculture the same in England and Australia, although the practice may differ? 5. What help does the science of chemistry give to agriculture? 6. How many chemical elements are of interest to the farmer ? Name them. CHAPTER II THE NATURAL KINGDOMS. 6. Before seeking further chemical information, we must understand two terms which are much used in speaking on agricultural matters ; they are organic and inorganic. 7. There are said to be three kingdoms in nature — the animal, vegetable, and mineral. In the animal kingdom are included all kinds of living creatures, whether they be birds, beasts, fishes, reptiles, or 10 PRINCIPLES OF" AGRICULTURE. insects ; as well as all things that are produced from any l)ortion of their bodies. Thus the wool off the sheep's Lack, the leather made from animals' skins, and the silk spun by the silkworm from its own body, are all animal productions, and therefore belong to the animal kingdom. 8. All kinds of plants, from the largest forest tree to the smallest moss, belong to the vecjetahle kingdom ; and all things obtained from plants, whether as food or cloth- ing, are also included in it. Now we know that the manure of animals is used by farmers to feed plants, and plants supply food for animals; so the animal and vegetable kingdoms help to make and support each other. 9. Everything that does not belong to one or other of these two kingdoms must be classed in the mineixd kingdom. Rocks, stones, metals, clay, chalk, salt, and coal are all called minerals ; and although this kingdom is very unlike the other two, yet it is closely related to them, for the rocks form soils to feed plants, and plants and animals have made rocks. Coal was formed many ages ago from forests of giant ferns. The chalk rocks consist of nothing more than millions upon millions of sea-shells firmly pressed together, and are therefore really animal remains. And the beautiful coral rocks are the skeletons of millions of little creatures called coral polypes. 10. In our daily food, the bread belongs to the vegetable kingdom, the milk or meat to the animal, and the salt to the mineral. In our clothing, the straw hat, and the calico shirt from the cotton plant, are of vegetable production ; the woollen-cloth jacket and trousers, and leather boots, of animal ; and the iron nails in the boots, and metal buttons on the other parts of oiir dress, of mineral. 11. An animal resembles a vegetable in some particulars. They both have life, only of a widely different kind; they both live and groio hy taldiuj in food ; and they both have certain parts of a paiticular form, whose special work it is THE NATURAL KINGDOMS. 11 to cliaiige the food iiito a real poilion of the Uving animal or plant; these parts are called the organs of the animal or plant. The roots, stem, leaves, blossoms, and fruit are fdant-Gvgans ; and the lungs, liver, heart, kidneys, and blood-vessels are a few of the many animal organs. 12. Minerals have no kind of life whatever, and there- fore no organs. Minerals are masses of unorganised matter having neither life nor motion, and do not increase. An animal is an apparatus of combustion, consumes oxygen, produces heat, transforms organised matter into mineral, and restores its elements to the air and earth. A vegetable is an apparatus of reduction, produces oxygen, absorbs heat, transforms mineral into organised matter, and derives its elements from the earth and air. Professor Charles S. Minot of Harvard defines the two primary divisions of the living world thus : ' Animals are organisms which take part of their food in the form of concrete particles, which are lodged in the cell protoplasm by the activity of the protoplasm itself;' and 'plants are organisms which obtain all their food in either the liquid or gaseous form by osmosis (diffusion).' The plant receives food passively by absorption, the animal has to obtain its solid part of food by active exertions. Being now able to distinguish these three kingdoms, we can see that the reason why all animal and vegetable substances are called organic is because they are portions of things which consist of organs ; and all other substances, mineral or inorganic, because they belong to the mineral kingdom, and have no organs. 13. For tlie terms organic and inorganic we could use the words organised and unorganised, but by a simple experiment we can best illustrate the difference. If we take a piece of wood, straw, bark, or similar material, and burn it in a candle flame, then the organised vegetable or organic part will disappear as smoke or gas, and the ash left is the inorganic or mineral part, and this 12 PRINCIPLES OP AGRICULTURE. is capable of lurther separation l)y analyses. The organic part burns, the inoi-ganic part does not burn. 14. If a portion of soil, previously dried, be put on a piece of metal (lig. 1) and heated to redness by the candle flame, the soil will turn black as the heat attacks and drives off the organic matte i', and as it disappears, a gray- ish, brownish, or reddish colour will be observed, tiiis being the mineral or inor- ganic part left. Any animal matter — wool, bone, flesh, cheese, &c. — can be tested Ijy this fire test, and the dark animal or organic matter will disappear, and the mineral or inorganic matter will be left. Questions. — 1. Wliat is meant by the terms organic and in- oiganic? Wlien organic matter i.s burned or decays, what takes place? 2. How would you separate the organic from the in- organic parts ? What is left after the fire test? 3. How many kingdoms are there said to be in nature? Do they help and support each other? 4. Give examples of the three kingdoms other than those noted in the chapter. Fig. 1. CHxiPTER III. FORMS OF MATTER. 15. Chemists have spent years in trying by every known means to separate all things into the simplest substances or elements of which they are composed ; and now it is found that there are about sixty-five eletuents in the world which cannot be broken up into any simpler substances. 16. Many of these elements are of very rare occurrence, while with several of them we are very well acquainted. Gold, silver, iron, lead, and suli)hur or brimstone are elements well known to us : tliey each consist of the FORMS OF MATTER. 13 one simple substance only. In this our section on agri- cultural chemistry, we shall only have to deal with fourteen out of the sixty-five elements, because they are all that are of any importance in studying the composition of soils, plants, and animals. 17. But we must not expect to find these elements in their separate or simple condition, for this is not the form in which they generally occur in nature. They exist in groups of two or more, firmly joined together in certain fixed proportions ; and these groups are called compounds. Common salt is a compound of two elements. Water is another compound of two elements. Sugar is a compound of three elements. And when the elements in each of these groups are closely combined together in the proper proportion to forui the compound, tlieir character becomes completely changed. Let us take water as an illustration of this : it consists of two elements, both of them gases — namely, oxygen and hydrogen : hydrogen gas will burn ; oxygen will not, but it will make other things burn much more brightly and fiercely. ISTow, water is a liquid — not a gas, and it will neither burn nor make other things burn ; on the contrary, it is the very thing that is used to put fires out. So we see that the compound — water — is not at all like either of its elements, hydrogen and oxygen. Water is decomposed by electricity into its two elements, and fig. 2 shows a convenient apparatus for making the experiment. If, for instance, the current of a battery is passed through water to which 14 PRINCIPLES OF AGRICULTURE. about y\- of its volume of sulpliuric acid lias been added, the water will be decomposed, and it will be found that half as much gas is collected from the positive pole as from the negative pole. The former is oxygen gas, tlie latter hydrogen. We must note that chemical combination takes place only in certain definite proportions by weight, and that in the combination no weight is lost or gained. Further, a chemical compound is alike in all its parts, and cannot be broken u^) by simple mechanical means. 18. All matter exists in one of three states — the solid, liquid, or gaseous. For instance, iron is a solid, water is a liquid, and air is a mixture of gases. But the same sub- stance may be made to assume each of the three forms : let us take water as an example. Under ordinary conditions, it is a liquid ; under the in- fluence of cold, it becomes a solid — ice; but if greatly heated, it assumes the in- visible and gaseous form — steam. And here we notice that heat causes a solid to become a liquid, and a liquid to change into a gas. We can, by subjecting water to different degrees of temper- ature, cause it to assume at our i)leasure any of the three As an experiment, put some lumps of shown standing in fig. 3 on the tripod stand. Apply heat, and water will be produced; continue the heat, and we will -get steam. By means of a bent delivery tube fixed into the cork the steam can be con- densed in the test tube standing in a glass of water. This condensed water may again be frozen by placing the test tube in a mixture of ice and salt in a tumbler. Irou, by Fig. 3. states mentioned, ice in a flask, as FORMS OF MATTER. 15 the same agent, heat, may be melted or changed from the solid to the liquid state ; and by still greater heat, it would actually become a gas ; in fact, iron gas really does form a part of the atmosphere of the sun. 19. Some gases are elements, and some are compounds. Hydrogen and oxygen gases, which together form water, are, as we have said, each of them elements. Nitrogen gas, wdiich forms four-fifths of the air we Ijreathe, is also an element. But carbonic acid gas is a compound, made up of two elements, carbon and oxygen. Ammonia gas is another compound, made up of two elements, both of which are gases — nnmely, hydrogen and nitrogen. Coal-gas is not one gas, but several compound gases mixed together. Atmospheric air, again, is neither a simple nor a compound gas, but a mixture of the simple gases nitrogen and oxygen, with a very small proportion of the compound gas carbonic acid, and just a trace of ammonia. A chemical mixture may be made up of any of tlie elements or compounds, and in any proportion. By such mixing they do not lose their old properties or acquire new ones, and no heat is given out in mixing or in making up tlie mixture. Besides air, soils and manures are examples of mixtures. 20. Again, some gases are soluble in water, and some are not. Carbonic acid and ammonia gases are very soluble, while f)xygen is only very slightly soluble indeed, and hydrogen and nitrogen are not soluble at all. 21. And now, if we understand that all the matter con- nected with our globe is composed of about sixty-five elements, a few of which are very plentiful, but three- fourths of which are scarce ; that these elements generally occur combined in twos, threes, or fours, in fixed propor- tions to form compounds, very unlike the elements which compose them ; and that these elements and compounds may exist in either the solid, liquid, or gaseous state, we shall be in a good position to continue our chemical studies. 16 PRINCIPLES OF AGRICULTURE. Questions. — 1. Define a chemical element, compound and mixture, and give examples other than those named in the chapter. 2. What are the elements of importance in agriculture ? 3. What elements compose respectively salt, sugar, ammonia, and carhonic acid ? 4. What is tlie difference between a chemical compound and a chemical mixture ? CHAPTER IV. ATMOSPHERIC AIR. 22. The ail* which surrounds our globe consists mainly of two simple gases, nitrogen and oxygen — about four times as much nitrogen as oxygen. A very small proportion of car- bonic acid gas is diffused in this mixture — about one measure in 2500 measures of air ; and yet this small pro- portion is really an enormous quantity altogether, because tlie space through which it is diffused is so extensive. Besides these, water-gas, or watery vapour, as we generally term it, is always present in the atmosphere, and in a much larger proportion than carbonic acid gas — about one measure in every hundred, more or less, according to the state of the weather. There is also always a trace of ammonia in the air."^ In this chapter, and the next two, we will discuss these substances — that is, oxygen, nitrogen, carbonic acid gas, water, and ammonia. 23. We all recognise that air occupies space, and every time the wind blows we feel the sensation of pressure. It is invisible and tasteless, and necessary for the process of respiration or breathing. When we inhale air, we use the oxygen in it, and in return send out from our lungs * Lately Professors Lord Rayleigli and Ramsay have discovered a new element in air which they have called Argon. It is tlie most inert sub- stance known, and is an element, or mixture of elements, having char- acteristic spectra. Its molecules are simple. The atomic or molecular weight is provisionally stated to be 40. Argon is more soluble in water than is nitrogen ; rain-water being relatively rich in it. ATMOSPHERIC AIR. 17 carbonic acid. Plants require air as much as animals, and under the influence of sunlight they absorb this carbonic acid gas, retain the carbon, and liberate the oxygen. In this way, aided by the movements we call winds, the composition of the air is maintained practically uniform. The presence of carbonic acid gas in the atmo- sphere is demonstrated by leaving a shallow vessel con- taining lime-water in the open air, when it will rapidly become turbid. Let us try two other experiments. If we press a test tube, held mouth downwards, upon the sur- face of water in a tumbler, the air, owing to its elasticity, will resist the downward motion, and when the hand is removed the test tube will spring upwards. Air when heated expands, and if we hold the test tube in the flame of a spirit-lamp for a short time, then close the open end with the thumb, and open it beneath the surface of water, the air having expanded while heating, will now contract on coming in contact with the water, and some of the latter will enter the tube, supplying the place of the air expelled by heating. Kain attains a certain amount of heat as it passes through the air, and is followed by a warm volume of air as it penetrates the soil, and assists the chemical processes which then take place. 24. Of all the elements found in atmospheric air we take Oxygen first, because of its great importance (symbol O, atomic weight 16). It is a kind of air or gas without colour, smell, or taste ; it will not itself burn, but if a lighted match be placed in it, the match burns with far greater brilliancy than in common air. It is the oxygen of the air which supports animal life, and enables substances to burn, the nitrogen serving only to prevent the too violent action of the oxygen. If a lighted candle be placed under a glass shade, so that no more air can get in than is already there, the candle burns for a time, but soon goes out for lack of oxygen gas. An animal placed in oxygen at first B 18 PRINCIPLES OF AGRICULTURE. Fig. 4. feels a glow of pleasure, but soon gets into a fever of heat, and really lives at such a rapid rate, that before long it dies. 25. Besides existing in the atmosphere, oxygen occurs in combination with all the rock-forming materials of the earth's crust, and constitutes by weight eight-ninths of the whole of the water on the globe. To obtain oxygen, mix together some powdered chlorate of potash and a very little of black oxide of manganese. Place in a test tube and apply flame of spirit-lamp (fig. 4). If a red-hot match be plunged into the tube while the melted potassic chlorate is effervescing briskly, it will burst 'into fall flame, aud burn much more brilliantly than it does in air. Oxygen is the great supporter of combustion, and metals undergo a slow process of combustion when exposed to the atmosphere — for example, iron getting rusty. Heat also causes iron to oxidise, as seen in the smithy scales. The metal magnesium will burn, if held in a spirit flame, with a dazzling light, and the oxide formed is the well- known calcined magnesia of the druggist. 26. Nitrogen (symbol N, atomic weight 14), like oxygen, . is a gas without colour, taste, or smell, and will not burn ; but, unlike oxygeu, it immediately extinguishes a lighted match ; and an animal placed in it is unable to breathe, and therefore dies. It is a very inert gas, as it does not combine readily with any other substance. It forms by far the largest part of the atmosphere, and its great use seems to be to weaken the power of the ox^^gen ATMOSPHERIC AIR. 19 by being mixed so largely with it ; and so animals are prevented from living, and fires from burning, at the fearfully rapid rate that they otherwise would. 27. Nitrogen is present in the native nitrates, such as saltpetre (potassic nitrate) and cubical nitre (sodic nitrate). Some of the compounds of nitrogen form our most useful foods ; others, such as quinine and prussic acid, are either valuable medicines or deadly poisons. Nitrogen is also amongst the most valuable sub- stances available for agricultural pur- poses. The gas is obtained for test pur- poses as shown in fig. 5. Put a small chip of phosphorus in a dish, and float it on a basin of water ; then heat a glass rod iu the spirit flame and touch the phosjihorus, and as it flames, place over it a wide-mouthed bottle, or a bell jar, as in fig. AVhen the flame ceases, and the bottle is cool, the air at the upper ^^^- ^* end will be found to be nitrogen gas, and if a burning match or lighted taper be introduced it will be extinguished. 28. Oxygen seems such a friendly sort of gas that it will combine with almost every other element without much difficulty ; but nitrogen seems so unfriendly towards it, that although they are in such close company in the atmosphere, they remain separate, and will not combine. There is, however, a terrible power that actually compels them to cling together ; and this power is the electricity ^vhich causes the lightning and thunder. During a thunder-storm a very small quantity of a nitrogen oxide, named nitric pentoxide,"*^ is formed from the nitrogen and oxygen ; and * The prefix pcni means 'five.' There are five oxides of nitrogen, con- taining respectively one, two, tliree, four, and five equivalents of oxygen ; this is the highest. Compounds containing four and five equivalents of oxygen go to form nitrates, the remainder form nitrites. 20 PRINCIPLES OF AGRICULTURE. this compound combines Avitli a little water to form nitric acid. Nitric pentoxide is often called nitric acid, but it is only when it is combined with a proper proportion of water that it becomes the true nitric acid or aqua-fortis of the chemist. 29. The little nitric acid that is thus produced in the air is dissolved in the rain and carried into the soil, where it supplies plants with a most valuable food. 30. Having seen that oxygen and nitro- gen compose air, we may by an experiment perform a rough analysis of air. Take a test tube graduated into five parts, and introduce a piece of phosphorus upon the end of a wire. Then invert the test tube in a tumbler of water so that tlie water in the tube and tumbler is level witli the IlllilflV ^^^'^ ^^ ^^^® graduated scale. In about illlBWHf^ half an hour the water will have risen lUHHKiF" one division in the scale (fig. 6). This experiment shows us that one-fifth of the air in the tube consisted of oxygen, and the remainder will be found to be nitrogen. Questions.— 1. What is the composition of atmospheric air ? What substances does it contain, either indispensable or of great value to plant growth ? 2. What is oxygen ? Describe an oxygen test. 3. Is nitrogen a valuable substance in agriculture ? 4. Where are oxygen and nitrogen present? Fig. G. CHAPTER V. ATMOSPHERIC AIR — continued. 31. Although there is oidy a small percentage of carbonic acid gas in the air, it has a special interest in agriculture, so ATMOSPHERIC AIR. 21 that ill this chapter we will study the compound, carbonic acid gas (symbol CO2, weight 44), and the element, carbon (symbol C, weight 12). Carbonic acid is a colourless, invisible gas, with a slightly sharp odour and taste ; hence its name — acid. It immedi- ately extinguishes a h'ght, and destroys animal life. Some- times it is called carbon dioxide, '"' which plainly shows that it is not an element like oxy- gen or nitrogen, but a compound of carbon and oxygen. Car- bonic acid is obtained in large quantity from calcic carbonate, which is the constituent of limestone, chalk, marble, shells, coral, &c., and is present in all natural waters..: It is the choke-"" damp of the miner, and is Fig. 7. given off in the fermentation of liquids and in the pro- cess of respiration. The gas can be made in the following manner. Fragments of marble about as large as almonds are placed in a bottle fitted with a tube funnel and a delivery tube bent at right angles, as shown in fig. 7, and * The prefix di means ' two.' There are two oxides of carhon, contain- ing resi^ectively one and two equivalents of oxygen. This is the higher 22 PRINCIPLES OF AGRICULTURE. after the addition of enough water to cover the marble, A little hydrochloric acid is poured down the funnel, and carbonic acid gas is evolved. Carbonic acid is much heavier than air, so that it is collected by displacement in a bottle. If a lighted taper be introduced, it will be extin- guished, and if the gas be passed into lime-water, it will be turned milky. The gas is a compound of carbon and oxygen, and is very soluble in water. 32. We have often seen and used carbon. The substance which is called blacklead, but which has no lead whatever in it, is a pure form of carbon. Its proper name is graphite or plumbago ; so that when we use a blacklead pencil, we are writing with carbon. Another pure and very beautiful and valuable form of carbon is the diamond. We may get a pure form of carbon by holding a cold plate down on the flame of a lamp or gas-jet ; the soot that will soon cover it is carbon. But a more common form than either of these, though not so pure, is charcoal. Charcoal is wood that has been only i)artly burned. The heat has driven off all the substances contained in the wood, except just tlie carbon and the very small proportion of ash which would have remained had the wood been completely burned. Coke is also an impure form of carbon ; it is coal with all its materials driven off as gas by heat, except the carbon and ash. About lialf the dry matter of all animals and plants consists of carbon. Combined with hydrogen and oxygen, it occurs in sugar, gum, oil, bone, and flesh. If we heat a piece of sugar on a tin plate, a black mass of carbon will be left. 33. Whenever Avood, coal, oils, and other substances which contain carbon are burned in the air, a great deal of the carbon combines with the oxygen of the air, and forms carbonic acid gas. Also, when animal and vegetable matter decays or rots away, carbonic acid is produced. And when animals breatlie, they take in the oxygen and nitrogen of the air and send out the nitrogen again unaltered ; but the ATMOSPHERIC AIR. 23 oxygen combines with some of the carbon of the food and of the worn-out parts of the body, and so they breathe out the poisonous carbonic acid gas. Whenever oil, tallow, or coal-gas is burned, carbonic acid gas and water are formed. Respiration produces similar changes, and in the expired air the same products are found as from the burning of food. "We can show that our breath contains carbon dioxide by blowing through a straw into lime-water, when it will become milky. Fortunately^ however, what is poison to animals is a food for plants. Their leaves absorb the carbonic acid, and the green colouring-matter of the leaves, in the. daylight^ very wonderftdly makes the carbon and oxygen part company, returning the latter and keeping the carbon to form a part of the plant itself. Plants thus feed themselves and at the same time purify the air for the needs of animals. 34. We next have to consider the water in the atmo- sphere. If you place a dish of water in the sun in summer, it soon gets dried up, as we say ; that is, the heat of the sun changes the litpiid water into invisible vapour — water- gas or steam. In this way our washed linen, and the puddles in our roads, are dried. But this evaporation takes place in cold weather as well as hot, though not to so large an extent. Evaporation goes on rapidly from the water of the ocean, and the vapour which rises forms the clouds that supply the earth with rain. The presence of moisture in the air is shown by the hoar-frost which forms on a glass or any vessel containing a freezing mixture. If we counter- poise say an ounce of powdered calcium chloride on a balance, and leave it some time, the salt will absorb mois- ture from the air, and we will see it by the beam showing it has increased its weight. Evaporation is one of the peculiarities of the Australian climate as compared with the English. It is accepted as a fact of leading importance that, abundant though the rainfall actually is, experience 24 PRINCIPLES OP AGRICULTURE. has proved tliat all over that country the evaporation is still greater than the rainfall. Questions. — 1, What are the sources of carhoiiie dioxide, and from -which of thein is it generally obtained ? Describe tlie pre- paration and mode of collection of the gas. 2. Wliat elements compose carbonic acid and nitric acid ? Under what circum- stances is the last named produced in the atmosphere ? 3. Explain the uses in the economy of nature of each of the constituents of air. 4. The composition of air is found to be very nearly uniform throughout. Give reasons for this. 5. What is the proportion of carbonic acid gas in atmospheric air? Is excess of this gas injurious to plants? CHAPTER VI. WATER. [In agriculture, water plays a very prominent part, and the agriculturist requires to give it even more attention than a chemical student.] 35. Water is a compound of the two elements, hydrogen and oxygen, in the proportion of two measures of hydrogen to one of oxygen. It is without any taste or smell when pure, and therefore does not flavour anything which is cooked or dissolved in it. This wonderful property which water possesses, of dissolving many substances, makes it the carrier of food for plants from the soil to all parts of the plant ; and for animals from the stomach to the blood- vessels, and thence to all parts of the body. It also forms as much as two- thirds of the weight of the living animal body ; and oftentimes a much greater proportion of the living vegetable. If we place a Iimip of sugar or salt in water, it wall disappear and be in solution. The liquid which effects the disappearance is called the solvent — that is, fat dissolves in ether, camphor in alcohol. If we evaporate the water in which the salt was dissolved, we will regain the salt. Some substances also are more Water. 25 Fig. 8. soluble than others— that is, before the water is saturated. As an illustration of the difference between substances in solution and suspension, mix together some black oxide of manganese and sugar, and put the mixture in some water, stir, and throw it on a filter (fig. 8). The black oxide of manganese being only suspended in the water, will remain on the filter, and the clear liquid which passes through will now taste sweet, showing that the sugar has passed into solution. 36. Water has certain per- manent features which make it of great service in agriculture. (1) Its abundance— it covers two-thirds of our globe, soils contain 20 to 40 per cent., air about J per cent., and 50 to 90 percent, of animals and plants are made up of water. (2) Its composition along with substances in solution. A few inches from the surface soil the roots of plants are like a network of root-hairs, and these retain what are impurities in pure water, though plant- food. Water which has passed through this network may contain calcium sulphate, calcium carbonate, and calcium nitrate. (3) Its dissolving power is so great that few substances resist it entirely. Ammonia, nitrates, chlorides, and compounds like sugar dissolve rapidly in it. Other substances, like gypsum and starch, less easily ; and some, such as sand, are insoluble. It is to this solvent power of water that the terms soluble and insoluble are applied in agriculture : thus a soluble phosphate is a phosphate that will dissolve in water like sugar or salt. (4) Its neutrality, as shown in it being neither acid nor alkaline, and hence having no injurious effect on most substances. 26 PKINCIPLES OF AGRICULTURE. (5) Its action under varying temperatures: as a solid, liquid, and gas, it affects and influences both plants and soils. (6) Its movability, as by gravitation it passes downward through the soil, and by capillarity it rises upwards, carrying both heat and plant-food. (7) Its circulation by evaporation from the clouds to the drains in the soil, then through rivulets, rivers, and seas, back again to the clouds. Water is nature's great food giver and carrier. Fig. 9. 37. The Hydrogen (symbol H, weight 1) contained in water is a simple gas like oxygen, without colour, taste, or smell. It will burn, but with a pale flame, unlike the bright wdiite flame of coal-gas. It is the lightest substance known — only a sixteenth the weight of oxygen ; so that, although there is twice as much hydrogen as oxygen in water by measure^ there is eight times as much oxygen WATER. 27 as liyclrogon by weigJit. The gas may be prepared by placing a few fragments of granulated zinc in a flask fitted as in fig. 9, and the end of the delivery tube must dip under the shelf of the pneumatic trough. Pour in some water till the flask is about one-third full, and then add a little strong sulphuric acid. Hydrogen will be quickly evolved, and the first portions must be allowed to escape, as they will be mixed with the air in the flask, and will be a very explosive mixture. If a lighted taper be intro- duced into a jar of hydrogen, it will be extinguished, but the gas will burn at the mouth of the jar. If a balloon be filled with hydrogen, it will rise upwards, showing it to be lighter than air. Hydrogen is a constituent of such sub- stances as starch, sugar, petroleum, coal, and ammonia, as well as of every animal and vegetable organism. 38. Ammonia (symbol H3N, weight 17) is a compound gas consisting of the elements hydrogen and nitrogen. It is very light, because it contains three measures of hydrogen to one of nitrogen. It has no colour, but it possesses the very powerful and pungent odour of smelling-salts. It also has a stinging, burning taste, and is very soluble in water. A strong solution of it will quickly raise a blister on the tongue. It is always produced when vegetable and animal matters decay, from tlie hydrogen and nitrogen which they contain; just as carbonic acid gas is produced from the carbon and oxygen which these same matters also contain. Ammonia is one of the most valuable substances a farmer can have in his manure or soil, because it contains nitrogen, one of the principal elements of plant food. Ammonia is popularly known as spirits of hartshorn. It is a constant ingredient in rich soils, especially clayey soils, which have a remarkable power of absorbing it. What is known as sal ammoniac is ammonium chloride, and if this and a solution of caustic potash be put in a dish and warmed, we will get the fumes of ammonia. Ammonia is best 28 PRINCIPLES OF AGRICULTURE. prepared by mixing together about three parts by weight of powdered quicklime with one part by weight of am- monium chloride, and enough water to make a thick paste. If the mixture be heated gently, the gas comes off freely, and can be collected, as shown in iig. 10. It is a strong alkali, and is extremely soluble in water, one volume of that liquid dissolving 800 volumes of ammonia gas. Ammonia is also produced by the destructive distilla- tion of such substances as horn, cheese, coal, &c. 39. We have in these chapters studied the four elements, oxygen, nitrogen, car- bon, and hydrogen, and the compound gases which they form, and which occur in the atmosphere. These elements and compounds form a very important part of agricultural chemistry, and should be ^^" ' well considered by those studying the principles of agriculture. Questions. — 1. By what characters may ammonia be re- cognised? 2. What are the sources of hydrogen in nature? 3. What are the principal impurities in spring-water, and to what is their presence due ? 4. What would be the eflect of applying a light to hydrogen when mixed with about one-third its volume of oxygen ? 5. If asked to show the great solubility of ammonia in water, how would you do it? 6. Some soil is shaken up with water. How could you prove that some of it has been dissolved ? CHAPTER YII. METALS. 40. The elements are very simply divided into two classes METALS. 29 - — metals and non-metals. Iron, copper, lead, gold, silver, (fee. are metals ; while sulphur, carbon, oxygen, &c, are non-metals. Metals are easily distinguished from non- metals by the peculiar glistening appearance which they all possess, so diiferent from any other kind of polish. This shining appearance is called metallic lustre. They are also good conductors of heat and electricity. Metals combine with oxygen to form oxides, with chlorine to form chlorides, and with sulphur to form sulphides. Some of the metals just named have nothing whatever to do with plant-growth, while there are several others without which plants cannot grow at all ; it is therefore to the latter that we shall restrict ourselves. 41. The metals which plants take up from the soil are potassium, sodium, calcium, magnesium, and iron. There is also one other — aluminium — which forms a part of all clay soils, and is of considerable agricultural importance, but is not taken into the plant. All these metals exist as compounds with non-metals in the soil, not as elements ; and therefore, bearing in mind what has already been said about chemical compounds being altogether different in their appearance and properties from the elements which compose them, we need not be surprised that we have never seen these substances as metal elements glistening on the ground. 42. Potassium (symbol K, weight 39) is a light metal, soft as wax, and in colour white, with a shade of blue. Potassium is found abundantly in nature, but solely in combination. It is found in granite and other igneous rocks, and as they crumble doAvn, finds its way into soils, which, if devoid of potash, are uniformly barren. The metal is a difficult one to prepare, and therefore costly, but a small fragment will do for experiments. If a small bit be heated in a small iron spoon, it will take fire and burn with a violent flame ; and if a bit be thrown on the surface of water, 30 PRINCIPLES OF AGRICULTURE. it will float and kindle spontaneously, burning with a beautiful purple flame. When combined with oxygen it forms jiotash, which is an alkali. Two other compounds are potassic carbonate and potassic nitrate. In its crude form potassic carbonate is known by tlie name of pot-ashes or pearl-ashes, and is prepared from the ashes of burnt wood. The common name for potassic nitrate is saltpetre, and in India and other warm climates its formation is constantly going on in the soil. 43. Sodium (symbol Na, weight 23) is, like potassium, a light soft metal, and both are difficult to get or keep in the pure state. It is abundant in nature in combination with chlorine as rock-salt, and in sea- water it occurs in solution in the form of common salt. Sodium compounds occur in most soils, and small quantities are found in the majority of land plants, but largely in those of the sea, as in kelp. If a fragment be heated in a spoon, it will burn with a yellow flame; and if a bit be thrown upon the surface of cold water, it will act like potassium, except that it will not flame. If it be tried with hot water, then it will flame with a rich yellow colour. Some of the compounds of sodium found naturally are sodic chloride or common salt, sodic nitrate or Chili saltpetre, which is deposited in the soil in many districts ; and sodic diborate or borax. 44. Calcium (symbol Ca, weight 40) is the metal contained in lime, and the metal itself is rarely seen. It is a yellowish-white metal, prepared by passing a galvanic current through fused calcic chloride. The oxide of the metal calcic oxide is quicklime or calcium and oxygen combined. If limestone, marble, oyster-shells, or chalk be treated with hydrochloric acid, carbon dioxide is evolved, and lime is left. Lime is applied to soil to increase its fertility, but the action of lime in fertilising soils is still a matter of dispute. Other important compounds of lime are gypsum, or plaster of Paris (sulphate of lime), and METALS. 31 phosphates of lime, wliich exist largely in bones as the bone-earth phosphates (tricalcic phosphate). 45. Magnesium (symbol Mg, weight 24) is a silver- white metal which, when heated to redness, takes fire and burns with a brilliant white light. It exists abundantly as magnesic carbonate in dolomite or magnesian limestone, and in many volcanic rocks. Magnesic oxide, or the common calcined magnesia, is the only known combination of oxygen and magnesium, and is obtained by ignition of the carbonate, as in the case of lime. Another compound is magnesic sulphate, often called Epsom salts. 46. Iron (symbol Fe, weight 56) is found in abundance, and the common ores are black oxide or magnetic iron ore, red oxide or haematite, ferrous carbonate or clay ironstone, and ferric sulphide or iron pyrites. Ferrous sulphate is the well-known salt, green vitriol. Heated in air, iron becomes coated with oxide in the form of scales — peroxide"^ of iron or rust. If the air be moist and contain carbonic acid, iron rusts in it at ordinary temperatures, but it remains bright in the absence of carbonic acid, no matter whether the air be moist or dry. 47. Aluminium (symbol Al, weight 27 -5) is a white body like silver, with a brilliant lustre, both malleable and ductile, is not oxidised in the air, and is the metal in alum and clay. Common alum is known as the aluminic potassic sulphate, and is a double salt. Clay is a combin- ation of a body called silica, the chief constituent of sand, with the oxide of this metal called alumina. AVe can obtain alumina if we powder some ammonia alum, put it in a crucible, and heat it strongly with the spirit flame. The ammonia will be expelled and alumina remains. All the clays of our arable soils are simply aluminic silicates. Questions.— 1. What is caustic potash, and how is it obtained ? * In this connection per means 'higher.' There is a lower oxide of iron called protoxide of iron— proto meaning 'lower.' 3^ PRINCIPLES OF AGRICULTURE. What occurs when potash is deficient in soils ? 2. Wliat are the natural sources of sodium? What happens when sodium is dropped on the surface of Avater? 3. What is the composition of limestone ? Name other substances of the same composi- tion. Explain what occurs when limestone (1) is strongly- heated, and (2) is placed in dilute hydrochloric acid. 4. What is the difference between a piece of limestone and a piece of lime? 5. Have acids any action on iron? What is iron rust? 0. What is tlie name of the metal which is contained in clay ? CHAPTER VIII. NON-METALS. 48. The non-metals with which we shall have to do in agriciiltiire are carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorus, silicon, and chlorine. The first four ^ve con- sidered in our chapters on air. With the next, Sulphur or brimstone (symbol S, weight 32), we are familiar, in both the forms in which it is sold in the shops — namely, in thick round sticks called roll-sulphur, and in a powder called flowers of sulphur. It is a pale-yellow, brittle substance, insoluble in water, and a bad conductor of heat. If we heat a piece of sulphur on a tin plate, it will burn with a blue flame and have a suffocating odour. It is one of the very few elements that are found uncombined in nature, and enters into the composition of vegetable and animal substances. 49. Phosphorus (symbol P, weight 31) is not found free in nature like sulphur, but it can be obtained from bones, which consist chiefly of phosphorus and lime. When pure it is in appearance very much like white wax. It has such an affinity for free oxygen that it burns — smokes, but does not take fire — in the air, forming phosphoric oxide, and therefore has to be kept in water. Lucifer-matches are NON-METALS. 33 tipped with a substance containing pliospliorus, to enable them to take fire when rubbed. Phosphorus occurs chiefly in combination with oxygen, calcium, and magnesium, in volcanic and other rocks, which, by crumbling down, form our fertile soils. It is a constituent of the plants used by man and animals as food. It is an important ingredient of animal structures, and exists in flesh, blood, milk, &c. It is a soft, transparent, pale-yellow solid, insoluble in water, and remarkable for its excessive inflammability. 50. Silicon (symbol Si, weight 28) is one of the most plentiful elements in the world ; it is never found in the free state, but occurs in nature combined with oxygen to form silica. Silver sand and quartz are silica ; the sand of the seashore and flint-stone are impure silica; glass also consists chiefly of silica. Silica is the only known oxide of silicon, and it occurs in a pure condition in quartz or rock- crystal. It is as abundant a substance in the mineral world as the analogous carbon is in the vegetable kingdom. 51. Chlorine (symbol CI, weight 35-5) is a yellowish-green gas, and if breathed, even in small quantity, causes a sore throat. Common salt is a compound of this element and the metal sodium ; the chemical name for common salt is therefore sodic chloride, and from it chlorine gas can bo obtained. It is never found free in nature, but in combin- ation, and can be prepared by heating a mixture of common salt, black oxide of manganese, and sulphuric acid. The most remarkable property of chlorine is its bleaching action, and bleaching-powder is a combination of slaked lime and chlorine. Questions. — 1. Where is sulphur found? Does it occur free or combined ? How is it possible to obtain sulphur from iron pyrites ? 2. In what combinations does phosphorus occur which are of value in agriculture ? 3. What is tlie cliemical nature of clay, gypsum, glass, and chalk? 34 PRINCIPLES OF AGRICULTURE. -^ ,_t. .2 -s i S ^ 1 1) 'X rt "2 <; C 1 ~ .2 "^ «3 d B o U B 11 g."S:2 1 liil s -O^ "o 'o ;4 s J 1 u. <«<*.»„ . >> ^ X ^5 X 1 o d o o^o6 o o o O < o II i ^6 c'G s 1 .2 c B .3 "b B .2 d 1 1 (2 w ^^^5 3 1 3 < 1 OXIDES AND SALTS, ACIDS AND ALKALIES. 35 CHAPTEEIX. OXIDES AND SALTS, ACIDS AND ALKALIES. 53. From our remarks on the metals and non-metals, it will liave been noted that oxygen combines with each of them, thereby forming their oxides ; and that more of them exist in the form of oxides than in the simple condition of elements. 54. There is yet another curious rule or law about these oxides, and a very important one too, and it is this : that oxides of the metals frequently combine with oxides of the non-metals to form compounds called salts. AVe are already familiar with one of these salts — namely, carbonate of lime or chalk. When chalk or limestone — that is, car- bonate of lime — is heated in the limekiln carbonic acid gas, which is an oxide of the non-metal carbon, is driven off; and lime, which is an oxide of the metal calcium, remains behind. This plainly shows that carbonate of lime consists of carbonic dioxide and calcic oxide, or in other words, of carbonic acid gas and lime. For these several reasons, we shall in these pages more generally speak of the oxides and salts, than of the metallic and non-metallic elements in their uncombined state. 55. The metallic oxides which thus form salts with the non-metallic oxides are called bases, and the non-metallic oxides which combine with them, acids. But the latter are not, strictly speaking, acids ; they are more correctly acid oxides ; before they become true acids they must combine with a fixed proportion of water. Water, by thus combining with these acid oxides, acts like a base. Ammonia, too, when united to water, acts like a base, and forms salts with the acid oxides, very closely 36 TRINCIPLES OF AGRICULTURE. resembling the corresponding salts of potash and soda in their properties. 56. Oxygen has, however, a kind of rival in chlorine. This element unites directly with the metals as oxygen does, and by so doing forms their chlorides. These chlorides are also called salts; as, for instance, common salt, which, we know, is sodic chloride. 57. Acids are bodies which have a sour taste, turn blue litmus red, and liberate carbonic acid when added to sodium carbonate. There are two kinds of acids, such as hydrochloric atcid, containing no oxygen ; and nitric and sulphuric acids, which contain oxygen. They are all colour- less liquids, and the three acids named can be neutralised by potash, forming potassium sulphate, or nitrate, or chloride. 58. Alkalies are another class of bodies which have a soapy taste, turn red litmus blue, and absorb carbonic acid. They have a powerful affinity for acids, neutralising them, and forming salts. If potash — which turns red litmus blue — be added gradually to sulphuric acid — which turns blue litmus red — the properties of both bodies gradually disappear, and at last a liquid is obtained — sulphate of potash or potassium sulphate — that has no action on litmus. 59. The substances called acids are also knowui as acid oxides, and form salts by combining with bases. The alkalies are termed basic oxides, and form salts by com- bining with acids. There is a third group — neutral oxides — sucli as water, carbonic oxide, and nitrous oxide, which do not possess a sour or soapy taste, do not change the tints of colouring matter, and do not combine with acids or with bases to form salts. Questions. — 1. If an alkali is added to an acid, what name is given to the product Avliicli is formed ? 2. Why is ammonia classed as an alkali? 3. What are the characteristic properties of acids and alkalies ? 4. Into what main classes may oxides be divided ? CARBON C031P0UNDS. 37 CHAPTER X. CARBON C03IP0UNDS. 60. Carbon compounds is the name given to a large class of substances met with in plants and animals, though not found in the earth, and treated of in books on organic chemistry. These bodies all contain carbon united Avith one or more of the elements hydrogen, oxygen, and nitro- gen. For example, oil of turpentine contains carbon and hydrogen ; starch contains carbon, oxygen, and hydrogen ; and gluten contains carbon, hydrogen, oxygen, and nitro- gen. Besides differing in composition, they differ in proper- ties. Some are acids, as vinegar and tartaric acid ; some are salts, as fat, tallow, and butter; and some are neutral bodies, as sugar, starch, or spirit. 61. As an illustration of an organic acid, we take tartaric acid, for it is found abundantly in the vegetable kingdom. Tamarinds, the pine-apple, and especially grapes, contain it. The chief source of tartaric acid is argol, an impure salt of tartaric acid, which is deposited during the fermentation of grape-juice. Tartaric acid contains carbon, hydrogen, and oxygen, is colourless, and easily soluble in water. When burned it will give off the smell of burnt sugar (caramel), and leave a residue of carbon. It will also turn blue litmus red. 62. Fats and oils are neutral bodies made up of an acid and a base, the base being in all cases glycerin, while the acid varies wdth the different fats and oils. Oils are liquid, and many of them are obtained from vegetables, either from the seed or fruit; for example, salad-oil, or sweet oil, is obtained by crushing olives, and linseed-oil from the seeds of the flax plant. The fats are solids, and are in most cases, 38 PRINCIPLES OF AGRICULTURE. such as tallow or suet, lard and butter, obtained from animals. Eoth fats and oils are insoluble in water, and lighter than water. If oil or fat be boiled for some time with a solution of caustic potash, the liquid becomes slightly milky, and nearly the whole of the fat dissolves and enters into combination with the potash, forming stearate of potassium or soft soap, while the glycerin which Was before combined with the stearic acid in the fat is iiow set free. All kinds of fat and oil are decomposed in the same way by the action of caustic potash. 63. Glycerin, we have seen, is the base of all fats and oils, and is a thick colourless licpiid with a sweet taste, dissolving readily in water. Heated with acids, it combines with them, and bodies resembling fats are formed. 64. By boiling fat with caustic potash (potash lye) we obtained soft soap or potassium stearate. Common house soap is made from tallow by boiling with caustic soda (lye), and forming stearate of soda. In manufacturing, when the liquid becomes a pasty mass, common salt is thrown in, and the boiling continued. Marbled or Marseilles soap is made when coarse olive-oil is used instead of tallow. The cleans- ing properties of soaps depend upon their power of dissolv- ing fatty matters, and the presence of free alkali increases the cleansing power, just as the presence of potasli or soda in water increases its solvent power. 65. As illustrations of organic neutral bodies, we take sugar and starch. Sugar is composed of carbon, hydrogen, and oxygen, the two being in the proportions in which they combine fo form water. It is, when pure, white, crystalline, and sweet, extremely soluble in water, and has no action on either red or blue litmus. It is obtained from the beet- root on the Continent, sugar-cane in India, America, AVest Indies, Java, and Australia, and sugar-maple in Canada. It does not combine with acids, but if boiled with them will become converted into grape-sugar. CARBON COMPOUNDS. 39 Q6. Starch is another neutral substance composed of carbon, hydrogen, and oxygen, and contained in tiie roots, stems, and seeds of plants, where it plays an important part in their nutrition. It is found in Avheat, rice, potatoes, maize, &c. It is a white powder which consists of dis- tinct granules having peculiar structures. Starch in its ordinary condition is insoluble in water, and gives a characteristic blue colour with iodine. Although it under- goes no change in the air at ordinary temperatures, if heated to about 160° C, starch is converted into dextrin ov British gum. Extract of malt brings about the same change, a fact which is taken advantage of in the malting of barley. 67. Gluten is a substance made up of the four elements carbon, hydrogen, oxygen, and nitrogen. About 70 per cent, of flour is starch, and 10 per cent, gluten, and these substances represent the two most important constituents of food. If flour is tied up in a muslin bag, and well kneaded in a basin of water, the starch will separate out, and give the water a milky appearance. When all the starch is thus removed, there will be left in the bag a gray sticky substance resembling bird-lime ; this is gluten. When exposed to the air in a moist condition, gluten soon decomposes — putrefies — and then smells like decaying cheese ; but when quite dry it may be kept without under- going much change. Questions. — 1. Wliat is the substance from Avhich tartaric acid is generally ol)tained ? Name the elements contained in tartaric acid. 2. Have the fats any resemblance to inorganic salts, such as nitre or common salt? If so, how? 3. How does glycerin behave Avlien heated with acids ? 4. Why is it that soap behaves so differently with hard and soft waters? 5. Where is grape-sugar found, and how does it differ from cane-sugar? Name the elements which sugar contains. 6. 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The nitrogen and ash ingredients, which occur in the soil as salts, become dis- solved in the rain-water, and in this state enter the root- hairs, which are really microscopic tubes. This weak Fig. 14. of Buck- wheat. GROWTH — OFFICE OF LEAVES. 57 Water-solution of the various salts* is tlie sap of the plant in its crude — that is, unprepared — state. In this condition it moves upwards into the stem, and along its ducts into the veins of the leaves. Roots have also the power in some degree of attacking and rendering soluble solid ingredients in the soil. This action takes place at the point of contact between the root-hairs and particles of soil, and is duo to an acid sap which the root contains. It explains how plants obtain their large supply of phosphoric acid and potasli, as these substances, especially phosphoric acid, are practically in an insoluble state in the soil, and rarely found in solution in the water present in soils, and which roots absorb. Roots have also a selective power, taking up larger quantities of some constituent in preference to another, which may really be more abundant — for example, preferring potassium to sodium salts. 96. Besides ash ingredients, roots also supply nitrogen to the plant, and this generally in the form of nitrates. Recent investigations show that in some cases the feeding power of roots is assisted by union with another organism, and Scotch investigators have shown that the leguminous plants have tubercles on their roots, and through their presence are able to gain nitrogen, derived from the free nitrogen of the atmosphere. The Scotch experiments have now been confirmed by several independent investigators. The character of these tubercles is as yet not known, but their action has been proved. When the seeds of peas, lupins, or vetches are sown in sterilised sand, containing all the ash constituents necessary, excepting nitrogen, the growth is small and dwarfed, and the roots have no tubercles. If a minute quantity of ordinary soil be added, tubercles appear on the roots, and the plant grows vigorously and * These salts are phosphates, carbonates, sulphates, nitrates, silicates, and chlorides of lime, potash, soda, ammonia, magnesia, and iron. (See table of salts, par. 52.) 58 PRINCIPLES OF AGRICULTURE. ripens. At harvest, on examination, it is found that the quantity of nitrogen present, both in crop and soil, greatly exceeds that originally present in sand, seed, and added soil. The conclusion arrived at is that through the tuber- cles nitrogen has been derived from the atmosphere. 97. If you look at a leaf, you will notice that smaller veins branch off from the central one in all directions, getting finer and finer as they near the edge of the leaf. By means of these innumerable branches, the crude sap is conducted into every part of each leaf. As yet, this sap has added nothing to the substance of the plant; none of it has actually changed into the fibre or solid matter of the plant itself. Now, however, the crude sap undergoes a wonderful change; but before attempting to explain the nature of this change which is carried on in the leaves, we must briefly describe the spaces which lie between the veins, as they appear when magnified a few hundred times under a microscope (fig. 15). 98. A leaf is covered on both sides with a thin skin, which, especi- ally on the under side, is full of exceedingly small breathing pores, or stomata (mouths). Between the upper and under skins, the leaf Fig. m— Transverse Microscopic Section consists of little cells of a Leaf: full of juice. The cells a, the outer skin covering tJie upper side ; ^i^^ contain minute b, layer of closely-packed cells; c, loosely- . p -r, i. n packed cells; d, outer skin covering the grams Ot CHlOrOpnyll, under side, showing stomata, e. which is the name given to the green colouring matter of leaves. Air-spaces exist between the cells. GROWTH — OFFICE OF LEAVES. 69 99. Througli the pores the leaves breathe in the carbonic acid gas from the surrounding atmosphere ; and the chloro- phyll grains, under the influence of sunlight^ in some wonderful way cause the carbon and oxygen of the carbonic acid to disunite. The leaves retain the carbon as plant- food, but allow the oxygen to pass out again into the air (par. 33). This decomposition of carbonic acid can only take place under the influence of sunlight, and therefore only goes on in tlie daytime."^ The action may be seen, as in fig. 16. Put a plant or a branch from a living plant in a tumbler of water. ^^' ' Add to the water a few drops of sulphuric or hydrochloric acid, and then invert the glass upon a saucer or plate, and place it in the sun. The plant commences immediately to extract carbonic acid from the water, the carbon is retained, and the oxygen will be seen distilling out from the pores of the leaves, gathering in globules, and rising through the water to the upper part of the glass. Plants without chlorophyll have no green colour, and cannot decompose carbonic acid — for example, common fungi and dodder. Fungi get their carbon from decayed vegetable matter in the soil, and dodder lives as a parasite on clover. 100. So we see the leaves are the meeting-places of the soil-food and air-food ; and they meet here for the special purpose of combining together. The carbon forsakes the company of the oxygen for that of the hydrogen and oxygen of the water in the crude sap, and forms with them the non- nitrogenous substances, starch, gum, and sugar. The three substances named, by union with the nitrogen, also con- tained in the crude sap, produce the albuminoids or nitro- * Under certain circumstances, the electric light seems to have the same effect. 60 PRINCIPLES OF AGRICULTURE. genous substances. The production of starch in sunlight can be illustrated by the following experiment. Gather a few leaves (the leaves of seedling cabbage plants answer tlie purpose) and keep them for some hours in a warm moist atmosphere in the dark. Then gather from the same plant, leaves that have had as many hours exposure to sunsliine. Examine both for starch by dipping them suc- cessively into boiling water, then into methylated spirit till white, next into cold water, and finally into a weak solution of iodine in potassium iodide. In addition to the starch and sugar just mentioned, the hydrogen, oxygen, and carbon combine to form the various acids that give the sourness to lemons, rhubarb, apples, grapes, and other fruits; and also to form the fats which occur largely in those plants which produce oil-seeds, and in a lesser degree in all other cultivated plants. A little ammonia is also absorbed from the air by leaves ; and this adds to the supply of nitrogen already brought into the leaves b}'' the crude sap, for the formation of the albuminoids. After a severe drought, when rain falls, a plant may also take in to some extent water through the leaf. 101. The stem and other parts of plants, which like the leaves have only a thin skin covering, and are green in colour, also have the power of assimilating carbon from the carbonic acid of the air, by means of the chlorophyll, to which their greenness is due. 102. But besides drawing in gases, the leaf pores (and especially those on the under side of the leaf) breathe out water vapour in the daytime, and more rapidly in strong sunlight. A sunflower gave off 22 ounces of water in 24 hours; and a maize plant in 105 days exhaled no less than 36 times its own weight of water.* Imagine, therefore, what must be the enormous amount of water given ofl* by evaporation from a whole field of a leafy crop such as beans, * Johnson's How CrojJS Groiv, page 275 (Macmillan & Co.). GROWTH — OFFICE OP LEAVES. 61 clover, or turnips. No wonder, then, that the soil of a field bearing a crop is always drier than that of a bare field. Sir J. B. Lawes of Kothamsted states that in growing a crop of wheat, for every pound of dry matter produced, 200 pounds of water were evaporated ; and for every pound of mineral matter assimilated by the crop, 2000 pounds of water passed through the plant. If we place a fresh plant under a dry glass, the glass will very soon show moisture on its inner surface. Again, if we place two glasses full of water side by side, and then place a fresh branch, with plenty of green leaves on it, in one of the glasses, the branch will suck up the water, which will pass off through the leaves in a far shorter time than the water will evaporate out of the other glass. 103. But this enormous loss of water by evaporation is the main cause of the crude sap coming up from the roots, through the stem, to the leaves. It rises by capillary attraction (par. 166), just as the oil in a lamp rises in the wick as fast as it is burned away at the top. The water which is used to supply the hydrogen and oxygen for the formation of the organic substances that are to make the new solid matter of the growing plant, will also cause a further loss of water, in addition to that by evaporation. 104. Wq will now have some idea of the great import- ance of leaves, as organs of plant nutrition ; for we have seen that they absorb carbon, far more of which is required by the plant than of any other element ; that by exhaling water, they cause the rise of the sap which conveys all other kinds of plant-food from the soil; and that they organise — that is, arrange and prepare — the different crude feeding materials into substances that can at once form a part of the solid tissue of the plant itself. In other words, leaves are largely the collectors of plant-food, and are at the same time the factories where plant-foods are prepared. 105. If we were to place all the leaves of a full-grown 62 PRINCIPLES OF AGRICULTURE. plant flat on the floor, touching each other, we would be surprised at the large area they would cover. Tlie sun- flower mentioned above had a total leaf area of 39 square feet. This shows how necessary it is for the welfare of a plant that the leaves should be in a healthy, well-developed condition. 106. The new sap, instead of simply being a weak solu- tion of certain salts, as the crude sap was, has lost a great deal of its water, and contains nitrogenous and non-nitro- genous substances, as well as mineral salts, for the making of the new parts of the plant that are formed in its growth. The sap is named the elaborated sap, to distinguish it from the cnide sap. The word ' elaborated ' means ' produced out of lahourj' and the sap is so named, because it is the result of the icorlc of the leaves. 107. Before following this sap in its further course through the plant, we should like to say a word more about the chlorophyll or leaf-green. Many experimenters have succeeded in growing and bringing to perfection oats and maize in bottles containing solutions of salts, composed of nitrogen and the essential ash ingredients. This mode of cultivation, as already noted, is called water-culture ; and by it, these persons have made several interesting discoveries about the ash ingredients ; one of which is, that if iron is entirely absent from the solution, no chlorophyll is formed in the leaves, consequently the leaves are white, and unable to decompose the carbonic acid of the air. Growth is at once checked for want of carbon food, and the plant gradually dies. And yet, strange to say, if only one drop of iron in solution be added before the plant dies, chlorophyll is formed, the leaves soon become green, and growth proceeds. This remarkable discovery proves, that although very little iron is sufficient, yet some is really essential to plant life and growth. Questions. — 1. What are monocotyledons and dicotyledons? GROWTH — OFFICE OF LEAVES. 63 What do you understand by plumule and radicle ? 2. What is the action of root-hairs ? 3. What special action have the tuber- cles of leguminous plants ? How is it proved ? 4. What is the action of chlorophyll? How do plants without it exist? 5. What action has the leaf of a plant? What can it inspire? 6. What do you understand by plant transpiration ? 7- AYhat is the difference between elaborated sap and crude sap ? CHAPTER XV. GROWTH — SAP MOVEMENTS. 108. The elaborated sap moves to all parts of the plant, partly by soaking from cell to cell, and partly along the ducts. It forms the juice of the young cells, and the sugar and starch which it contains are easily converted into the cellulose, or cell coverings, which is really the tissue and woody fibre of the plant. If the leaves are not full grown, some of it remains in them to form the new portion that is yet to be produced. Some of it goes down to the roots to increase the size of those already in existence, and to furnish the material for the growth of new feeding-roots. Also in its journey downwards, some remains to increase the bulk of the stem. And much of it moves upwards to supply the requirements of the buds from which the new portion of the stem, the new leaves, the blossoms, and the fruit or seed will spring. 109. But the order of the sap movements in these different directions is not the same in all plants. It depends entirely upon the number of seasons a plant can live. We can divide plants, according to length of life, into three classes : Firsts Those that do all their growing, and produce and ripen their seed, in one year, and then die. Second, Those that take iivo years to grow and ripen their seed before they die. And fhird, Those that live €4 PRINCIPLES OF AGRICULTURE. through a number of years, and produce seed each year. Those of the first-mentioned class are termed annuals ; those of the second, biennials; and those of the third, perennials. For instance, the grain-crops and beans and peas are annuals; they ripen in one year, and then die, and require to be sown again for the next year. Root- crops, and most clovers, are biennials ; they produce their seed at the end of the second season, and then die. And all kinds of trees, and most of our meadow-grasses, are perennials ; they will produce fruit or seed each year, and yet continue to live through a number of years. 110. Let us take a wheat plant as a type of all annuals; a turnip and a clover plant as examples of biennials ; and an apple-tree as a specimen of a perennial. By following the movements of the elaborated sap in each of these instances, we shall get a fair insight of its workings in all our cultivated plants. 111. From the leaves of the young wheat plant, the sap goes into the stem, and thence downwards to the roots, and upwards into the bud, supplying it with material for the formation of the unfolding leaves and growing stalk. Before long the ear appears, and growth now proceeds at its most rapid rate, till the plant is in full bloom. And now all the energies of the plant are devoted to the formation of the seed; the sap completely forsakes the leaves, and as a consequence, they fade and die; the roots cease to absorb food from the soil ; and all the sap in the stem rises into the ear to form the seeds. The soliihle non-nitrogenous substances (such as sugar) and the solnhle albuminoids, which together compose the milky substance in the unripe grain, become changed, by the ripening influence of the sun, respectively into insolahJe starch and gluten, such as we obtained from the wheaten flour (pars. 85 and 86). 112. And now that the plant has completed its work, GROWTH—SAP MOVEMENTS. 65 and the sap has all been changed into solid matter, let us see how the substances are shared between the seed and the rest of the plant. The seed contains by far the greater portion of the nitrogen and phosphoric acid ; while the straw contains the greater part of all the mineral substances, except the phosphoric acid. The carbon from the air, and the hydrogen and oxygen of the water, have formed the whole of the cellulose of which' the straw (minus the ash) consists; and of the starch, of which nearly six-sevenths of the seed is composed. 113. We now turn to the turnip to teach us something of the sap movements in biennial roots — turnips, swedes, mangels, beets, parsnips, carrots, &c. The crude sap and carbon are elaborated in the leaves much in the same way as they were in the wheat plant ; but on leaving the leaves, the whole of the elaborated sap moves downwards to the root. The work of the first year seems to be to gather as rapidly as possible all the crude plant-food from the soil and air, and to store it in the root in the elaborated forms of non-nitrogenous and nitrogenous sub- stances and salts for the second year's work. Consequently there is a great enlargement of the tap-root. 114. In the second year of the turnip's life, it throws up the flower-stem ; the many branches of which bear a fine show of yellow bloom, and afterwards the seed. The root supplies the materials for the second year's growth ; and in so doing, exhausts itself. In the formation and ripening of the seed, the same changes take place as in the formation and ripening of grain. But as the farmer grows the turnip for food and not for seed, he secures its roots at the end of the first year, when it has gathered its store of food from the soil and air. 115. In the clover plant, a great deal of the elaborated Bap of the first season's production is stored in the stem for the second year's groAvth. But as the leaves of the E 6^ PRINCIPLES OF AGRICULTURE. clover do not die at the end of the first year, but continue green through the winter, it cannot be said that growth is quite suspended. Still, very little progress is made during the winter; but in spring the elaborated sap already in the stem rises quickly, and causes a rapid development of stem and new leaves. The roots and leaves, too, rapidly collect crude food, which is as quickly prepared for the formation of the seed. But here again the farmer's object is to secure food for his cattle, and not seed; so he cuts it while it is in full bloom, when the leaves and stem contain the greatest amount of nitrogenous and non-nitrogenous substances, and before any of them have been utilised for the formation of the seed. 116. The apple-tree will next engage our attention, and it will teach us something of the movements of the elaborated sap in perennial plants. This sap moves from the leaves to all parts of the tree to enlarge the roots, trunk, and branches, and to form the fruit; but after the fruit has been produced, the whole of the elaborated sap that is in the leaves moves into the trunk, Avliere the soluble substances are stored in an insoluble condition between the wood and the bark till the following spring. The leaves thus deprived, as it were, of their life-blood, die, and fall to the ground. The spring sun calls the tree into life again by making soluble once more the insoluble substances which were deposited in the stem, and thereby enabling them to rise and make the buds burst into new leaves. 117. We know that a great deal of sugar is obtained in Canada from the maple-tree, and as it is a striking illustra- tion of what has just been said above, the practice will be briefly explained. In the fall of the year, much of the non- nitrogenous matter of the sap is deposited inside the bark as starch ; it would therefore be useless to pierce the maple-tree in the winter for the purpose of obtaining sugar; but in GROWTH — SAP MOVEMENTS. 67 spring tliis starch is converted into sugar, ready to move upwards to feed the buds, and therefore at this time tlie tree is pierced, and the sap, rich in sugar, trickles out, and is collected, and prepared for household purposes. 118. Some annuals may be made to assume the character of perennials by cutting off their blossoms each time they appear, and thereby preventing the exhaustion and conse- quent death of the plant, which occurs when the seed is allowed to form and mature. In this way a mignonette plant (which in Britain is an annual) may be made to grow into a little shrub, and to produce a succession of its sweet- scented blossoms for many years. Questions. — 1. What is the difference between annuals, bi- ennials, and perennials? Give examples of each not noted in lesson. 2. What do the seeds of an annual for the most part contain ? 3. What part of a biennial plant is of service to the farmer? 4. What perennial plants are grown on fruit farms? 5. To what classes do the following plants belong : Potatoes, hops, tares, rye, vines, sngar-cane, sugar-beet, rice, cabbage, kohl-rabi, maize, and lucerne? CHAPTER XYI. BLOSSOMS AND THEIR FUNCTIONS. 119. It is very interesting to notice the special purposes which blossoms fulfil in the work of seed production. We are apt to look upon them merely as objects created to feast man's eye with their beauty, or his nose with their sweet scent. Such, however, is by no means the chief purpose for which they exist. 120. If we examine an apple-blossom (fig. 17), com- mencing at the outside, we find some little green leaves — sepals, wrapping the bloom bud round for protection, and inside these the flower-leaves or petals, blushing a lovely 68 PRINCIPLES OF AGRICULTURE. delicate pink-and-red colour. As these spread open, they expose to view several slender little rods standing np from the centre, each with a little knob at the top. The thread- like rods are named stamens, and the knobs anthers. If now the open blossom be cut down through the centre, the thickened top of the bloom stem, which forms the base of the flower, will be divided, and the tiny emhrno apple pips will be exposed to view; so this is really the seed-case or young fruit, which, together with its tapering neck, is known as the pistil. The top of the Fig. 17.— Section of Apple-blossom: pistil at this early stage is not a, a, sepals ;?), b, petals ; c, stamens ; entirely closed, but has a d, the five carpels of pistil; e, j^^j^ute opening leading down ovary. r o o to the seed germs ; the mouth of this opening is called the stigma. In the buttercup, blackberry, and many other blossoms, the pistil stands up like a cone in the centre of the petals, instead of being below them as you see it in the apple, pear, or plum blossom. 121. The essential parts of the blossom are (1) the pistil, and (2) the stamens with their anthers. The anthers when matured burst open, and set free a cloud of fine dust called pollen; and these pollen grains arc the fertilising elements of the flower. When one of them falls on the stigma, it sends down a long slender shoot into the pistil, and thus comes in contact with the embryo germ ; the result being that the germ begins to develop, and in due course matures into a living seed. Unless this contact takes place the embryo will perish, and the seed-case will perish too, for its development is entirely dependent upon the develop- ment of the germ or germs it contains. BLOSSOMS AND THEIR FUNCTIONS. 69 122. We now nntlerstaiid the cause of so many tiny apples and plums, almost immediately after blooming time, fading and dropping ofl' the tree. It is not always easy for the pollen grains to fall upon the stigma of themselves ; the wind is an active agent in carrying them from flower to flower, for in summer time the air is full of pollen. But more eiBfective agents than the wind are the bees and insects, which probe the flowers for the nectar they contain, and in so doing cover themselves with the pollen of one flower, and press these grains on the stigma of the next one tliey visit, carrying away in turn some of its pollen to deposit on a third. This is the reason why the yield of fruit trees has often largely increased by the introduction of bees into the neighbourhood. 123. If the blooming time be wet and cold, the bees remain at home, and the pollen grains do not fly about, neither will they develop under such uncongenial con- ditions; consequently fertilisation does not take place, and as the gardeners say, 'the fruit does not set.' It is often thought that as long as there are no frosts at blooming time to kill the embryos, the bloom will 'set;' but from what has been said, it will be seen that it is just as necessary that the weather should be such as to favour the work of tlie pollen grains. It should also be noted that some plants, like the cucumber and maize, have their stamens and pistils in different blossoms ; and others, like the hop and willow, not only contain them in different blossoms, but even have these different blossoms on different plants. We now see that the reason why the pip of a certain kind of apple will not produce an apple-tree bearing the same kind of fruit, is, tliat it has been cross-fertilised with the pollen of some other I'lant of a different character; and so we learn that ever- increasing varieties is Nature's law in the vegetable world. 124. We shall now go back to the bee to learn the first great purpose of the coloured petals of flowers. The bees 70 PRINCIPLES OF AGRICULTURE. sally forth in search of nectar to store away as honey for future use as food, and also for pollen to feed their larvae on. They find both in the flowers which are made con- spicuous to them by their showy petals ; and so the flowers, as it were, tempt the bees unconsciously to help them to reproduce themselves by the combined means of pretty sights and dainty fare. Questions. — 1. What special purpose do blossoms fulfil in the work of seed production ? 2. Point out some broad distinctions between the grasses, legumes, and roots. 3. What is 'seed?' Why are the best samples of milling wheat and malting barley frequently failures when used as seed ? 4. Describe the ])arts of a flower. 5. What do you understand by flower fertilisation ? CHAPTER XVIL FARM-SEEDS. 125. A knowledge of plant-life is of great practical use to the farmer. It teaches him the necessity of pro- curing a fine moist bed for his seed, and also the need of shallow sowing in a close clay soil that will not readily admit air. It also points out to him that seeds buried too deeply in the soil may not germinate for want of oxygen, or may be exhausted before the plumule can reach daylight ; and that the principle should be that the smaller the seed, the less should be the depth of earth with which it is covered. From it he learns the importance of encourag- ing a healthy leaf development, and that blooming time is the time to cut his grass or clover in order to secure them in their most nutritious condition. It also shows him the value of the various parts of a plant for both feeding and manurial purposes. 126. But when the farmer has carefully prepared his {■ARM-SEEDS. 71 soil by cultivation and manuring, to receive the seed, it is still necessary, if he would be successful, that he should sow good seed ; and that he should only grow crops that are adapted to the soil and climate of his farm, because these only will come to perfection and give a profitable yield. We must, therefore, give some attention to our common farm-crops, and the conditions under which they are most successfully grown. 127. It is well known that well-ripened new seed is more active and productive than older seed. The seeds of some plants actually lose their power of growing if kept longer than the next season ; others retain their vitality much longer; but all sooner or later become quite nnable to germinate. Dishonest seedsmen frequently mix their stock of worthless old seed with the new, so as to sustain no loss by it, and at the same time, not to be easily found out in the fraud they are practising on their customers. 128. But there is another important consideration in choosing seed for sowing — namely, its pedigree. By this is meant a certain excellency of character, which has been established by a careful selection, year after year, of seeds possessing this excellency, and by a careful cultivation of them in a fertile and suitable soil, and in a favourable climate. In fact, seed of good pedigree simply means well-bred seed. This is the way in which the best varieties of our several farm-crops have been produced; and it is also the way in which our cultivated crops were first obtained from wild plants. 129. There is a wild grass {J^gilops ovata) which grows along the French and Italian shores of the Mediterranean, which, when cultivated in a fertile soil for a few years — the best seed being selected each year for sowing the next — produces seed resembling wheat-grains. AVheat has been cultivated for so many thousands of years, that it cannot be positively stated that this particular grass was the original 72 PRINCIPLES OF AGRICULTURE. parent of wheat, but there is no doubt that all our varieties of corn were derived from wild grasses such as this sea- shore grass. 130. Agahi, all our cultivated plants of the turnip and cabbage tribe were derived in like manner by careful selection and cultivation from one or more species of wild Brassica, which have spindly woody roots, bitter leaves, and both Avoody and bitter stems, quite unlike the large roots or heads of our cultivated turnips and cabbages. 131. Our potatoes too, with their large and mealy tubers, are the offspring of the wild potato, which grows on the coast of Chili in South America, with only tiny bitter tubers. By selection, and good cultivation, in more fertile soils and colder climates, our present varieties have been produced ; but if they were removed to the Chilian coast again, and allowed to run wild, they would soon degenerate into their former worthless condition. 132. Beets, mangels, carrots, parsnips, onions, and clovers — all liave been similarly derived from wild plants, gener- ally of little or no value in their uncultivated state. 133. We have said that some crops flourish better on certain soils, and in certain climes, than others. And it is to the farmer's profit to cultivate only those that are adapted to his soil, and will thrive under the climate of the place in which his farm is situated. Nutritious food- plants, both for animals and man, can be grown on almost any soil, and in almost any climate. The reindeer of the Arctic regions finds sufficient nourishment for its own support and for that of its Lapland master, in the lichen which grows beneath the snow. The Scotch farmer can grow the most nutritious oats in a climate of low summer temperature that would fail to ripen wdieat. The K'orth German can grow good crops of nutritious rye and mealy potatoes on poor shifting sands that would fail to grow other crops profitably. t'ARM-SEEDS. 73 134. We have now some knowledge of the substances in the aiu and soil which serve as plant-food. The carbonic acid in the atmosphere which plays such an important part, we can demonstrate by exposing clear baryta or lime-water to the air, and observing the film of barium or calcium carbonate which forms. An important factor in plant-life is the influence of depth and distribution of roots. Deeply-rooted crops, such as wheat, rye, lucerne, sainfoin, red clover, rape, and mangel, are subsoil feeders, and have a greater power and range in which to obtain food constituents than shallow-rooted plants such as barley, potatoes, and turnips. Shallow-rooted crops appropriate food accumulated at the surface ; deep-rooted crops bring up available food from the subsoil. Questions. — 1. From what plants are our common farm-crops descended? 2. What influence has depth and distribution of roots in plant-life ? 3. What is the action of rain-water in the soil ? 4. How do plants assimilate nitrogen, and what nitrogenous substances in the soil act as plant-food ? 5. How is a plant exhausted during the formation of seed, and what is the general structure and composition of seeds ? 6. Hoav does the respiration of plants affect the formation of organic matter ? 74 PHYSICAL PROPERTIES OF SOILS. [3. Soil Physics. — Soil considered as a mass of small particles of various sizes — Circumstances which determine the total surface of the particles, and the pro2)ortion of the space betiveen them — Influence of porosity of the jmrticles— Hardness, specific gravity, and physical characters of qiiartz-sand, limestones, clay, and humus — Difference in adhesiveness of coarse and very fine sand — Clay, a mixture of extremely fine sand and a small quantity of a colloid body ; evidence for this — Coagulation of clay hy lime — Differences in physical characters of soil according as clay is coagulated or uncoagtdated — Action of dressings of lime or chalk on heavy land — Humus, its origin ; 'roughly divided into hiimin and humates — All humates colloid bodies — The principcd cement- ing materials in soil, clay, and humates ; their action separately and together — So-called ' heavy ' and * light ' soils ; their physical characters, hoiu improved — Effect of the treading of sheep — Ex- planation of terms such as ^loam,' ''clay,'' ^ marl," '■peat.^ Circumstances which determine the capacity for water of soils when saturated — Adhesion of water to surfaces ; capillary attrac- tion — Capacity for water of soils when drained — Evaporation from soils when saturated; influence of time of year — Evapoirdion from soils ivhen drained — Circumstances in which water is brought to the surface by capillary attraction — Influence on evapjorcdlon of looseness of texture, of stories, of surface-cultivation andmidch- ing, of crops and tveeds — Practical cqjplications of these facts ; effect of ploughing, summer cultivation, hoeing, rolling — Wet and dry soils — Influence of subsoil on soil moisture — Water level in subsoil — Treatment of ivet and dry soils— Influence of draining, and of farmyard manure. Heat from chemical action, example of hot-bed and damp hay- rick — Aynount of heat from this cause — Heat from the sun — Influence of atmosphere — Great influence of angle of incidence of sun's rays ; aspect of fields — Mean temperaftcre of soil, its varia- tion with climate — Maximum and minimum temperature of surface soil coinpared with that of the air^Influence of colour on amount of heat absorbed^Night radiation — Specific heat of WHAT ARE soils'? 75 ivater, humus, clay, limestone, and quartz-sand, reckoned both on iveight and volume; its influence on soil temperature — Con- duction of heat hy soil constituents; influence of fine or coarse division, loose or firm texture, dryness and wetness — Prepon- derating influence of water on soil temperature — Loss of heat hy evaporation — Warm and cold soils — Effect of draining on tem- perature—Temperature of the subsoil at various depths.] CHAPTER XVIII. WHAT ARE soils'? 135. We shall now consider the soil — that of which our gardens and fields consist, and which we sometimes call dirt, earth, or mould. What is it made of 1 Some say, of decayed roots, and stems of plants of various kinds; and decayed manure which has been dug in, year after year. And this is right as far as it goes, for these things do help to make the soil. In some places, as in the middle of Russia, in Manitoba, and in the peat-bogs of various parts of this and other countries, there are soils composed almost entirely of decayed vegetable matter. But generally speak- ing, the great bulk of the soil would have been there, if none of these things had been added. 136. If we take some dry soil in our hand, and crumble it as fine as we can, it will be found that some of it is . in the condition of a very fine powder, some of it in the form of tiny grains of sand, and some in the form of little stones ; and if we look on the ground, we may also see a large number of stones of various sizes scattered about. It may be that even the powder feels gritty and has a glisten- ing appearance, which shows that it is only very fine sand. 137. But perhaps it is nearly all in a powdery condition, soft to the touch instead of gritty, and when moistened and squeezed, holds together and becomes plastic or soapy, so that it may be moulded into any shape. Such a soil would be called clay. 76 PRINCIPLES OF AGRICULTURE. 138. Now we can easily see that the sandy soil is com- posed of little else than stones, though they may be as small as dust-grains. But what are stones 1 They are bits of rock. The dust-grains, the sand on the seashore, tlie larger pebbles, the stones of which houses are built, are all pieces of rock. And even clay is only a certain kind of rock, which has softened down till it feels like putty. 139. Soil may be composed of any material that is not hurtful to plants if it has such consistency as will enable it to retain and slowly circulate water. In nature the most opposite substances are used as soils — such as sand, clay, peat, and chalk — and we know now, from water-culture experiments, that the black matter of soils or even the soil itself is not absolutely essential. A mixture of sand and clay is called loam. That there is a difference in soils we all recognise without being trained farmers. If we walk across a clay paddock after a shower of rain, Ave will soon have the clay adhering to our boots ; and if we are on a sandy stretch of land, it will shift beneath the feet, and not show itself on our boots. 140. By mechanical analysis (par. 182), which is simply the separation according to size of the particles of rock which form soils, we can obtain some idea of their com- position. The following are samples of such mechanical analysis : MECHANICAL ANALYSIS OF SOIL. Clay. Loam. Sand. Soil. Subsoil. Soil. Subsoil. Soil. Subsoil. Stones. 10-45 -63 15-63 30-55 Gravel 753 236 764 3267 706 5-11 Coarse sand 15'14 I'Sl 8-14 8-30 81-67 85-81 Fine sand 18-48 18*50 30-22 10-50 9-27 3-62 Clay 48-40 76-70 38-37 17*98 2-00 546 100-00 100-00 100-00 100-00 100-00 100-00 Questions.— 1. How can you prove that there are different WHAT ARE SOILS? 77 kinds of soils by handling, and then by walking upon them? 2. What do you understand by mechanical analysis ? 3. If a soil is simply a mass of small particles of various sizes, from what are they derived ? CHAPTER XIX. LAVA AND PEAT SOILS. 141. There are two kinds of soils that have not, like alluvial soils (par. 212), been transported or carried across the surface of the country from one place to another ; nor are they formed from the great mass of rock beneath, like stationary soils (par. 211), but lie upon it. They are lava and peat soils. We shall first speak of lava soils. 142. Physical Geography teaches us that there are certain kinds of mountains that have been thrown or pressed up by the fire and heat that are raging beneath the surface of our earth, and that some of these have large openings called craters at their tops, through which they throw up from time to time showers of ashes and streams of lava. These mountains are named volcanoes. The molten lava flows down their sides, sometimes in such large quantities as to fill the valleys, and cover the plains below for many miles. In South America, Italy, New Zealand, and many other parts of the world, this is going on noiv. But there are many other parts where old volcanoes, which no longer throw out their fiery substances, are still to be found with their fields of lava all around. Such extinct volcanoes, as they are called, extend across the middle of Scotland, and occur in the north of England, in North-west Whales, in the north-east of Ireland, and in Australia and Tasmania. And from the lava which they poured out thousands of years ago, very fertile soils have been formed. 143. In order to explain how this takes place, we must 78 PRINCIPLES OF AGRICULTURE. bear in mind that lava is simply molten rock — that is, rock which has been melted by the fierce heat of the fire within the earth. As it flows down the sides of the mountain, and over the surface of the ground below, it gradually gets cold, and once more hardens into rock ; but not such compact rock as before, for it is full of gas, air, or steam bubble-holes ; and, in shrinking as it cools, becomes cracked in all directions. In this state it is easily acted upon by rain, frost, and heat, and is slowly crumbled into a fertile soil. In the colony of Victoria, the soil derived from these volcanic eruptions is of great fertility and of exceptional value for agriculture. The natural vegetation growing on such a soil is of a most luxuriant subtropical character, forming a serious impediment to selectors opening out virgin land. These soils have a dark-red colour called 'chocolate,' and this is a tint that is considered to indicate a good quality of soil. Soils formed from these volcanic rocks are much sou girt after in Australia. The following analysis shows the composition of some of these soils of volcanic origin in a new country : SOILS OF VOLCANIC ORIGIN. Victoria. New South Wales. Queensland. Warrnambool Warrnainliool Burrawang Mackay Black Loain. Chocolate Soil. Red. Forest Soil. Moisture 12-860 0-720 7-610 I 22-720* i 11-71* Organic matter. 21 -880* 17-760* and alununa ) 11072 42-270 6-70 Lime r078 0-459 0150 0-92 Phosphoric acid. 0*088 154 0-102 0-47 Potash, soda,^ magnesia, &c. j 1104 0-168 1-12 Silica, sili-Kg.^og cates, &c. ... ) 68-731 26-980 79-08 100-000 100-000 100-000 100 00 Nitrogen = ammonia, 0-627, 0-437, 0-415, 0-29. LAVA AND PEAT SOILS. 79 144. The other overlying soil we have to describe is peat. In Chapter XYIII., we said that in some parts of Russia, Manitoba, and many other countries, the soil consists almost entirely of decayed plants ; this soil is called peat. Large tracts of peat are found in Ireland, Scotland, England, Russia, Germany, France, and in all the northern countries of Europe. In Ireland they are called bogs, and in Scotland and England, peat-mosses. There are nearly three millions of acres of peat in Ireland— :- that is, one-seventh part of the whole country. 145. In some places, bogs or peat-mosses extend over very large, flat, low-lying plains, and look like either wide brown moors or green marshes. In others they are met w^ith in smaller patches, in hollows of hilly districts, and are then of a darker colour. Peat-beds vary in thickness from a few inches to 30 or 40 feet. In some places the peat- bed is so firm and dry, that it can be ploughed and tilled, and will produce good crops of turnips, potatoes, barley, and oats. In other places it is just firm enough to walk on by picking your way between the wet places, but you can feel it shake under you as you walk along. When in this condition, it is often covered with coarse grass and heather. There are, however, other places where it is so soft and Avet, that if you were to venture on it, you would sink lower and lower into a kind of dark mud, until com- pletely buried and lost. 146. In the districts where peat is found, it mostly forms the chief kind oifuel. In the summer-time men cut it out with spades, and lay it in heaps to dry in the sun. It takes some time to get quite dry, as it contains a large quantity of water. This is not restricted to the British Islands, but can be seen, for instance, in Denmark, where the absence of any coal-bearing strata makes the inhabitants more dependent on peat. The men and carts often have to stand on boards, that they may not sink into it. 80 PRINCIPLES OF AGRICULTURE. 147. Wherever there is a peat-raoss, there must have been first of all either a marsh or shallow lake, for standing water is the great cause of the production of peat. But marshes are formed on low-lying levels, where water collects from higher ground, and where the soil is of a clayey nature, and will not let the water soak through. Lakes are also formed in hollow places, whence the water which collects from the surrounding hills cannot easily flow away. Hence these are the places where peat is formed. 148. Very soon water-plants of different kinds begin to grow thickly all over the marsh, and all round the shallow edges of the lake; and mud gathers about their stems. As these die, others spring up, and especially a kind of moss — sphagnum — which sucks up water like a sponge, and throws out new shoots as the old moss plant rots away. Year after year, fresh moss plants grow on the top, and the old ones get pressed down tighter and tighter as they decay, till at last the place of the water in the marsh is, in a great measure, taken up by this decayed moss or peat. At last, larger kinds of water grasses and plants grow on the now firmer surface, and as they decay each year, a still firmer surface is formed. Such is the story of peat formation in what was once a marsh. 149. In the case of a shallow lake, the moss and other plant growth begins on the shallower margin or border, and gradually extends inwards till the whole of the lake is filled up. In some places this peat formation may actually be seen going on now, much in the same way as described. On the outside of the lake you may find the peat firm ; as you go towards the middle, it becomes softer and wetter ; and in the middle there is water still — the only remaining part of the former lake yet to be filled up by vegetable growth and decay. LAVA AND PEAT SOILS. 81 At the bottoms of these peat-mosses, the shells of the fresh-water shell-fish, which lived in them while yet they were lakes, are still to be found ; and the remains of old canoes have also been found, which were at one time used to carry their owners across these very lakes. 150. The peat at the top is a mass of fibre — that is, consists of a quantity of thread-like material thickly matted together ; while that at the bottom, through having decayed more, and been pressed tighter by the weight above, has lost this fibrous character; it is darker and more solid, and when dried, heavier. Peat as commonly known in Europe is not found in hot countries, though swamps and marshes abound, as in warm regions the decay of vegetable substances after life has ceased is too rapid. A peaty soil will be one that con- tains a large proportion of organic matter, but it is possible for a soil to contain too much organic matter for agricultural purposes. The following is the analysis of a peaty soil : Organic matter,* and loss on heating 64-66 Oxide of iron and alumina 13-96 Carbonate of lime 1-80 Potash, soda, magnesia, &c -98 Insoluble silicates and sand 18-60 100-00 Questions. — 1. What do you understand by an overlying soil? 2. What is a volcanic soil? Is it of any service in agri- culture? 3. How is peat formed? W^hat is the valuable con- stituent in a peat soil ? CHAPTER XX. HUMUS AND STONES. 151. By analysis we find that all soils contain some vegetable matter; and this matter is very much like * Containing 2-47 nitrogen = 2-99 ammonia, 82 PRINCIPLES OF AGRICULTURE. peat— dark brown, soft to the touch, and generally damp. It is called humus. The fallen leaves of trees in autumn are often gathered, placed in heaps, and left to decay. In course of time they rot, and become changed into a dark- brown, soft, moist mould, called leaf-mould. This is the substance — humus — that has just been mentioned. As leaf-mould it is much used in the cultivation of ferns and flowers. Humus is formed in ?mcultivated soils by the decay of all the parts of the wild plants which grow on them ; and in cultivated soils by the decay of those parts of the plants that are not required for food, such as the roots and stubble of corn and clover crops. So, of course, the more fertile the soil, and the greater the crops grown, the larger will be the quantity of humus formed. The dark-brown colour of most soils is due to the humus which they contain ; and because the richest soils generally contain most humus, some people have .thought that it is the cause of the richness ; but this is a mistake, for it is the richness of the soil that is the cause of the large quantity of humus being present. 152, Still, humus does improve a soil in many ways. Being somewhat spongy in its nature, it is able to suck up and retain moisture ; and by so doing, helps to keep a soil cool and moist in hot, dry weather. It also helps to make a sandy soil less gritty, and better able to keep manure from being washed througli it; and a clayey soil less soapy. It acts as a cement in sandy soils, holding the particles together, and in a clay soil it increases the porosity. Humus is the principal nitrogenous ingredient of soils, and to it is due the fertility of virgin soils. But above all, it forms food for plants when it has completely decayed. We will note a well-known instance of this : 153. Clover has very long and very many roots, and they go down a great depth into the soil. As they decay, they HUMUS AND STONES. 83 form a valuable manure or food for the next crop that is planted in the same ground, especially if it be a crop with deep roots like the clover. Wheat is of this char- acter ; and so it has become the custom to sow wheat after clover, as it has been found in practice that wheat always thrives well after it. And the reason is, that its deep roots find a good supply of a certain kind of food which it nnich requires, through the decay of the clover roots yielding humus, with the store of nitrogen in their root nodules. 154. All our soils except peaty soils are, at first, merely tiny particles of rock, which are crumbled from its surface by the action of water, frost, and heat, or dissolved from it by loater and air together. 155. And in nearly all soils there is still a large store of rock yet to be acted on year after year for ages to come by the water, frost, and air. This is the large store of stones, some smaller than pins' heads, and others as large as hens' eggs, which are present in all but. peaty soils. And being small and scattered, they are in a more suitable condition to be acted upon, and made into useful soil, than rock in its massive state. People often look upon stones as useless, but such is not the case ; for the tiny chips soon break up under the action of frost, and are partly dissolved by the carbonic and other acids of the soil, and so form a part of the real soil, which can be sucked up by the roots of plants to feed tliem and make them grow. And even the large stones must in course of time, though very slowly, decay, and also form a most useful part of the soil. 156. Alluvial soils generally contain those smooth rounded stones which we call pebbles ; they have been carried from their native rocks, by rivers or glaciers, and laid down in their present positions. They were, first of all, like all other stones, rough and cornered, but by being constantly 84 PRINCIPLES OF AGRICULTURE. knocked and ground against each other by tlie force of the water, they have become changed into smooth pebbles. Hard flint-stones are found in tlie more crumbly or U2:)per chalk, as it is named ; and fields can be seen so thickly covered with them that the soil can scarcely be seen. The farmers say that this covering of stones keeps the soil beneath from being dried up as quickly as it otherwise would be by the summer sun. The presence of stones on the surface of land tends to diminish evaporation and conserve heat. Other soils, such as those formed from the harder lime- stone rocks, contain stones which are pieces of the parent rock beneath. Many clay soils are made much more open and more crumbly by the stones they contain, and are therefore more healthy for plant-growth, and easier to till. Thus we see stones are not such worthless things in the soil as people are sometimes apt to think. 157. Humus as found in soils may be said to be composed of humin — the insoluble humus substance — and humic acid, which combines with various elements and forms liu mates. We can obtain both humin and humates by performing the following experiment. Place some powdered garden soil on a filter, and pour upon it a weak solution of ammonium carbonate. The insoluble humates will be decomposed, and pass into the filtrate as ammonium humate ; the humin will remain on the filter unchanged. On adding an excess of calcium chloride to the filtrate, the humic acid is precipi- tated as calcium humate along with calcium carbonate. It is better to use ammonia in place of the carbonate if the soil will yield a dark-coloured solution when so treated, as in this case the calcium humate can be precipitated without the carbonate. Humic acid is a strictly colloid body, and cannot, therefore, directly serve for the nourishment of plants. We must remember that the term humus is given generally to the brown or black organic substance in soils, and that this substance contains geic acid (gP, the earth), HUMUS AND STONES. ^5 hiimic acid (humus, the ground), ulmic acid (uhnus, an elm), and crenic and apocrenic acids (Tcrene, a spring). The dis- tinguishing feature of all these compounds is their power of retaining ammonia Avith great tenacity. A pure peaty soil, as such, is of little use in agriculture, and this can be judged of from the fact that of the 5000 flowering plants of Central Europe, only 300 of them, mostly rushes and sedges useless to the farmer, grow naturally on peaty soils. Questions. — 1. How is humus? formed in a soil, and what is its value as a plant-food ? 2. Are stones of any value or service in agriculture ? 3. Of what use is humus in a soil ? What is the difference between huniin and humates ? CHAPTER XXI. PROPERTIES OF SOILS. 158. By the term 'properties of soils' is meant, the various powers which soils possess. For instance, it is the property of soils to supply plants with food. Soils also have the power to hold moisture. But they have other properties besides these. All soils have not the same properties, because they do not all consist of the same proportions of sand, stones, humus, lime, and clay, and are not all formed from the same kinds of rock ; but the functions of all soils are alike — namely, to fix plants, to provide food, and to be a medium of chemical action on behalf of plant-life. 159. Plants cannot feed on solid food, as animals can. They live entirely on the carbonic acid gas which they absorb from the atmosphere by their leaves, and on liquids, which they suck up through the tiny hairs which cover the young thread-like roots; and since these hairs are so fine that they cannot be seen without the aid of a microscope, we can readily understand why 86 PRINCIPLES OF AGRICULTURE. no solid matter can be taken in by such very tiny mouths. Now this teaches ns two great truths about plant-food : firstly, that it must he soluble in icater ; and secondly, that there must he loater present to dissolve it, he/ore the plants can take it in. 160. We have already learned that rain-water, by the help of the carbonic acid gas which it gets from the air, is able to dissolve mineral substances that pure water cannot. It has also been discovered that some mineral substances can be very slowly dissolved by the juices of the root-hairs. And so, whatever substances in the soil can be dissolved by rain-water, or the jnice of root-hairs, can be carried into the plant; and what- ever substance will not thus dissolve, cannot be carried into it ; and therefore the real plant-food in the soil is the soluble matter. It is only a very small part indeed of even a good soil that is soluble plant-food ; but yet the other part has its use, for it has to hold the plant hrmly in the ground, as well as to keep the water and soluble soil ready for the plant to feed upon ; and in course of time some of it also will dissolve and become plant-food. 161. If we were to take three flower-pots, and fill the first with marbles, the second with sand, and tlie third with fine soft powdered earth, and then jjour water into them, we would find that the water would run through the pot with marbles, almost as soon as we poured it in ; but that it would take a little longer to run through the one containing sand, and still longer to soak through the third. This shows us that the finer the particles of the substance, the longer will it hold the water; and why? Because small particles lie so much closer together than large ones, that the spaces between them are too small to let the water run through quickly. The larger the PROPERTIES OF SOILS. 87 proportion of space there is between the particles of soil, the greater will be the porosity of the soil ; and the more porous a soil is, the less power will it have to retain water. Xow, clay consists of very fine particles - — finer particles than any other kind of soil — therefore it is able to hold water for the use of plants better than any other soil. But the fine particles of clay may be pressed together so closely when damp, that no water is able to get through at all ; this is not good for plants. A field with an under-soil of clay in this closely-pressed condition would not allow the water to pass downwards, but would cause the top to remain soaked with stale water, which is poison to plants. Sucli land is very cold, and also ver}'- unhealthy both for people and animals to live on or near. Schloesing's experiments teach us that humus has the greatest, and sand the least capacity for retaining water. Fine sand saturated with water and drained retained 7 per cent. ; a clay soil, 35 per cent. ; and a forest soil, 42 per cent. Light sandy soils thus suffer most from drought. The deeper a soil is, the greater will be its water-retaining power. 162. Depending on the absorptive power of a soil is the property of transpiration or evaporation. A soil which can retain little water will evaporate water most, and a soil which has the greatest capacity to retain water will evaporate it the least. So that the property of evaporation in a soil varies inversely to its absorptive power. Soil also has the power of absorbing water from damp air, known as hygroscopicity, and this depends on the fineness or tilth of the soil. Experiment shows that dry sand in one night absorbed nothing, while loam absorbed 3 "5 per cent., heavy clay i'l per cent., and garden mould 5*2 per cent, of moisture. 163. Soils have other properties besides the power of holding moisture, and supplying plants with dissolved 88 PRINCIPLES OF AGRICULTIIRR food. We will note some of the most important of them in this chapter. We took three flower-pots for our last experiment ; we will take this time two barrels with holes in their bottoms, or two vessels about 20 inches in depth, fitted with per- forated bottoms. Let us set them up, so that we may be able to catch the water which comes through ; and we will fill the one with sand, and the other with powdered clay soil shaken down well. We will next take some of the dark-brown or nearly black nasty-smelling water that runs from a manure heap, and pour part of it into each barrel. We shall find that it comes through the sand first, but is not so dark in colour as it was when poured in. The part that was poured on tlie clay soil takes much longer to soak through, but when at length it does find its way to the bottom of tlie barrel, it is quite clear and without smell or taste. What has caused this change ? 164. The manure which was in the water, and gave to it its dark colour and nasty smell, in going very slowly through the soil, has gradually stuck to the fine soft particles, till at last nothing but the clear water is left to reach the bottom. Here, then, is another property of tlie soil, especially of a clay soil — that it can hold manure, even soluble plant-food, for the use of crops. Charcoal — especially charcoal made from animal remains, such as burnt bones — has this power in a still more wonderful degree; and for this reason, water-filters, through which many people let their drinking-water pass before using, are partly filled with it. The charcoal keeps back much that is unpleasant and bad in the water, and thus makes it pure and wholesome to drink. 165. This retentive power of soils for plant-food is of the utmost importance in agriculture. If a solution containing phosphoric acid, potash, or ammonia, be poured I>tlOPERTIES OF SOILS. 8d on a quantity of fertile soil, the water which passes through will be found not to contain the substance originally in solution. The action is due to mechanical adhesion and chemical affinity. Salts are retained by mechanical adhesion, and can be easily removed by washing with water; for example, nitrates and chlorides. When chemically retained, they cannot be washed outj and the retentive power is exercised by the hydrates of ferric oxide and alumina, the hydrous silicates of alu- minium and humus. Phosphoric acid is chiefly retained by ferric oxide ; alumina also acts in the same manner, and both have a partial retentive power for ammonia and potash. The permanent retention of potash and other bases is due to the hydrous silicates of aluminium. The presence of carbonate of calcium assists in the retention of ammonia and potash, when in the form of chlorides, nitrates, or sulphates, as the acid combines with the calcium, and the base is left. This power of retaining plant-food is an important factor in giving soils their fertility. Clay soils show the most, and sandy soils the least retentive power. 166. There is yet another curious property that soils possess in common with many other substances : it is the power to cause moisture to spread through its particles in all directions, even upwards. Water sinks doivnwards by its own weight, but will also spread upwards by a power called capillary attraction, which means, 'the drawing power of hair-\\\Q tubes.' 167. Wg have all seen this power at work over and over again. Directly the end of the cotton-wick of a lamp is put into the oil, the oil begins to spread up the wick, and con- tinues to do so until it reaches the top ; and as fast as the oil burns away at the top, more comes up from below, till it is all used. Or again, persons often place flower-pots in saucers, and instead of watering the flowers which are in the pots at go PRINCIPLES OF AGRICULTURE. Fig. 18. tlie top, tliey pour a little water into the saucers ; and very soon this is drawn or sucked up, as you would say, by the mould in the pot. If a schoolboy had made a large blot on a copy-book, how would he dry it ? He would not lay the blotting-paper on it flat at once, and spread the blot larger ; but just let the tip of it touch the ink, and suck it up. The best illustration we can have of capillary action is the rise of a coloured liquid in white blotting-paper, or when a corner of a lump of sugar is dipped in a cup of tea or coffee, and it sucks the liquid up. The operation of this force can be seen as in fig. 18. Here we have two sheets of glass brought closely together at the dark edge of the diagram (A). The sheets are parted at B, are farther apart at C, and about one -sixth of an inch apart at the outer edges. If this glass be placed on a wet surface, the moisture will rise up and curve as seen in the diagram. 168. It has been noticed that if fine sand be put into one long glass tube, and powdered clay into another, and the ends placed in water, the Avater will quickly rise to a height of nearly 2 feet in the sand-tube, and more slowly to a height of 3 feet in the clay-tube ; but if coarse bits of clay or sand are used, the water will scarcely rise a foot. And so we learn that the smaller the spaces between the particles of soil, the higher will moisture rise ; and that clayey soil not only has the power of keeping water from running downwards quickly, but also, when dry, can draw it up from below to a greater height than sandy soils. 169. Capillary attraction depends on the distance between the particles of soil, and differs with the texture of soils. It is greatest in loam or clay, and least in open sandy soils. It PROPERTIES OP SOILS.. 91 is dependent oil the particles of soil being so fine and close together that the spaces between the particles make very fine tubes ; the word itself is from the Latin capiUus, a hair. However dry and parched a soil may be, if we dig down, we will come to the water-level line — called water table — beneath which the soil is saturated with water, and from this line upwards the soil will show varying degrees of moistness till on the surface it is dry. This dryness is due to evaporation, and if the cultivated soil is kept in a state of fine tilth, this fineness of the soil tex- ture would enable water to be drawn from the saturated section up- wards (fig. 19). Again, well working the soil has another action. By assisting capillary action, water might be brought up in a hot climate or Fig. 19, droughty season to such a, water table; B, section of capillary an extent that the under- ground store would not be able to supply the demand, but by frequent stirring — lioeing or liarrowing — the capillary tubes are broken a little below the surface, and the action for a time is interrupted. The mould in cultivated soil acts as a soil mulch, and, like a layer of leaves, grass, or farmyard manure, protects the moisture beneath. Some soils will attract water up- wards for 10 or 12 inches, others 16 or 18 inches, above the surface of the water-level. Questions. — 1. What are the functions of a soil? 2. State what you know regartling the absorptive power of soils. 3. What do you understand by capillary attraction? How can you illustrate it, and what service does it fulfil in soils ? 4. Have action ; C, continuity of the action broken by cultivation. 92 PtllNCIPLES OP AGRICULTURE). soils a retentive power ? If so, to what is it due, and on what substances is it exercised ? 5. How have peaty soils been formed? What are the general characteristics of these soils ? C H A P T E E XXII. CONDITIONS OP FERTILITY. 170. \Ve have now learned that plants require certain food substances from the soil ; and that these must all be in a form that can be easily dissolved, so that the tiny roots may be a1)le to suck them up ; therefore if a soil is without any one of the substances, it is so barren that it will not grow a blade of grass. And if they are present, but not in a soluble form, then, too, the soil is equally barren ; for although the substances are present, the plants cannot absorb them in their insoluble state. And yet it is necessary that a fertile soil should contain a quantity of even this insoluble matter, because, little by little, it becomes changed into soluble plant-food — mainly by the action of the carbonic acid in the water of the soil — and so helps to Icee}! the soil fertile. 171. 'Soluble 'and 'insoluble' matter is also spoken of as ' active ' and ' dormant ' matter, but a better term is ' available ' and ' unavailable ' plant-food. The object of a farmer in ploughing and working his land is to provide that, as the available plant-food is absorbed by his crops, fresh supplies of available food may be got ready. The fertility of a soil depends on the amount of plant-food available — that is, able to be assimilated^ or rendered soluble, by the juices of the tips of the roots. We must be careful not to put too much stress on chemical analysis of soils, for its only practical value is that of comparison. An analysis may show the presence of a high percentage of potash or phos- phorus, but if this percentage is not in the actual form and CONDITIONS OF FERTILITY. 93 condition imperative for plant-life, the soil would be tempo- rarily barren. Another fact regarding available plant-food which must be borne in mind is that an excess of one substance will not make good the deficiency of another. If a soil contains no available phosphorus or potash, abund- ance of available nitrogen or lime will not make it fertile. The proportion of plant-food present in an extremely fertile soil is very small. The first 9 inches of pasture may con- tain 0*25 per cent, of nitrogen, and arable soils 0'10-0'15 per cent. The same depth may show 0-20 per cent, of phosphoric acid and TO per cent, of potash. Now an acre of arable land, 9 inches deep, will weigh, when dry, 3,000,000 or 3,500,000 pounds, and if we suppose it to contain O'lO per cent, of nitrogen or potash, then the quantity in 9 inches of soil will be 3000 to 3500 pounds per acre, probably nine-tenths insoluble. 172. There are some things that are poisonous to plants, and if present in a soil in sufficient quantity, will make it unfruitful or perhaps quite barren. Thus a soil may be rendered poor, not only by having an insufficient supply of one or more of the substances which plants need for their growth, but also by containing other substances which destroy plant-life altogether. Salt is one of those substances which renders many soils barren when present to a large extent, as in many districts in Australia. The proto-salts or lower salts of iron will also make a soil unfruitful when present in large quantities. And stagnant water, and certain organic acids which are produced by the decay of vegetables in wet or marshy places, will make a soil sour and unfit for the growth of common farm-crops. As a rule, the organic acids which contain in their composition a small amount of oxygen are injurious. 173. No soil can be called good that is not well drained — that is, through which water cannot pass gradually but easily downwards. For, as noted above, stale water is very 94 PRINCIPLES OF AGRICULTURE. hurtful to plant-life ; and if all the little pores or holes in the soil are filled with stale water, there is no place for the fresh rain-water with its carbonic acid, and so it is obliged to run off the surface. Neither is there room for the air to enter, to help the growth of seeds, and to improve the soil. The land also is kept colder than it would otherwise be, and so the crops grow and ripen but slowly. A gravelly or sandy subsoil provides good natural drainage, but a clayey subsoil requires artificial drainage. 174. And yet a soil should not allow the water to pass through it too quickly, otherwise it gets parched and dry, and lets the soluble plant-food be washed through with the rain, out of the reach of the roots of the crops. To prevent these mishaps, the soil should either contain a good share of soft clay particles, or of humus, both of which suck up moisture and retain it for a long time. 175. Then again in texture, a soil should be firm enough to hold plants tightly in the ground, and not to be blown away as dust, with strong winds. At the same time it should be friable, that is, crumbly enough to allow the roots to spread easily in all directions, and also to allow the air, warmth, and rain to get into it. A loamy soil is of this character ; and good cultivation, such as ploughing, grubbing, harrowing, and rolling at the right time, tends to produce til is healthy condition of texture. 17G. There is yet one other cause that may prevent a soil being fruitful, and that is, an usuitable climate for the growth of plants. Such is the case in the deserts, and in the countries in the cold north. In the former they have no rain, and in the latter, not enough of the sun's warmth. The temperature of the soil itself is influenced somewhat by its colour. Whitish soils throw off the sun's heat, while (lark ones absorb it. Also, as above stated, undrained soils are colder than drained ones. Colours of soils are due a great deal to oxides of iron and humus. Red and yellow CONDITIONS OF FERTILITY. 95 are due to the presence of similarly coloured iron oxides, and tlie change in colour of a subsoil from bright yellow to a rusty brown is due to the yellow oxide of iron becoming oxidised. i\gain, chocolate and black soils, and all the darker shades, are due to the presence of humus or organic matter. 177. The conditions of fertility may be said to be : (1) sufficient depth of soil for plant-growth ; (2) plant-food in an available form ; (3) the soil must be mechanically suitable ; (4) able to absorb and retain sufficient moisture ; (5) the subsoil must be suitable ; and (6) all substances injurious to plant-life be absent. The indications of fertility are the natural growth and vegetation of the country, and the strength and character of weeds. The appear.! nee of a crop is not to be taken as an indication of iertility, but rather as indicating a farmer's ability to till land and produce crops. Questions.— 1. Wliat do you understand by active and dor- mant matter, and what other terms could you enjploy ? 2. What are the conditions of fertility? 3. What are the indications of fertility ? 4. What inHuonce has colour, climate, texture, and porosity on soil fertility? 5. AVhat substances are injurious to plant-growth when present in excess in the soil? CHAPTER XXIII. CLASSIFICATION OF SOILS. 178. Soils may be classified according to the amount of suitable plant-food which they contain, as (1) Rich or fertile; (2) intermediate; (3) poor; (4) barren or sterile. 179. In the last chapter we saw that many conditions are necessary to make a soil fertile ; but that the chief one is, that all the required ash ingredients of plants and nitrogen must be present in an available form. A detailed 96 PRINCIPLES OP AGRICULTURE. chemical analysis of the soil made by an agricultural analyst would show us what ash ingredients were present in the soil, and tlie percentage he found soluble in water or weak acids. The following analyses show the nitrogen obtain- able from the organic matter, and the mineral bases and acids contained in five different soils. The poverty of a soil is generally due in the first instance to scarcity of nitrogen, in the second to scarcity of phosphoric acid, and in the third to scarcity of potash. A soil would be con- sidered rich in nitrogen or phosphoric acid if it contained as much as half an ounce in 100 ounces. 180. CHEMICAL ANALYSES OF SOILS. Rich Fair Poor Poor Poor Alluvial. Clay. Sand. Peat. Chalk. Organic matter 12 ll'O o'O 49-0 2-3 yiekling Nitrogen [-5] [-4] [-2] [-7] ['1] Potash I'O -7) .o i.n +,.o«« o 1 OA , [ -3 ro trace Soda 2-0 -1 ) Lime 4-0 4-2 -1 ) ^.^ j 50-0 Magnesia I'O trace trace i ( '8 Peroxide of Iron 8-0 10 0) ^.^ ,^.^ - Almmna 320 ,34 0^ Carbonic Acid 6-0 8-4 '3 ... 24-0 Phosphoric Acid '5 '3 trace -06 '2 Sulphuric Acid I'O 1*0 1-2 Silica 30-0 31-0 870 35-0 207 Chlorine 1'5 Loss in analysis 1 3 8 "94 -1 100 100-0 100-0 100-00 100-0 The alumina and silica contained in the first two soils show that they consist of clay (silicate of alumina) to more than half their weight. The body of the third is quartz sand. The fourth is half vegetable matter, with a con- siderable proportion of sand and a little clay; and the fifth, three-fourths of carbonate of lime with 20 per cent, of sand. The first is rich in nitrogen, phosphoric acid. CLASSIFICATION OF SOILS. 97 and potash; the second fairly well off; the third poor in each; the fourth poor in phosphoric acid and potash; and the fifth poor in nitrogen and potash. As a general rule, it may be mentioned that a first-class soil should contain : Nitrogen, not less than 0*250 Phosphoric Acid, .. u 0-150 Potash, .. .. 0-200 Lime, .i .. 0-400 Chlorine, not more than 0-035 181. The style of farming and mode of tillage depend upon the mechanical composition of a soil — that is, the relative proportions of sand and clay which compose it. MECHANICAL CLASSIFICATION. Per cent, of Clay. Per cent, of Sand. 1. Clay, consisting of from 80 to 100 from 20 to 2. Clay loam, „ ,- 60 „ 80 .3. Loam, „ .. 40 .. 60 4. Sandy loam, .i n 20 n 40 5. Sand, .. .. .. 20 182. If an ounce of dried sifted earth be thoroughly shaken up with a pint of water and allowed to stand for a short time, the sand will fall to the bottom ; the water in which the clay particles are suspended must then be quickly poured off, and the sand again washed if the clay be not all removed. The sand can then be dried and weighed, and the class of the soil at once determined. 183. Soils are also classified according to their chemical composition, as 1. Organic or Peaty, consisting mainly of vegetable matter. 2. Siliceous, n n silica or quartz sand. 3. Calcareous, ti n carbonate of lime. 4. Aluminous, n largely of silicate of alumina or true clay. G 40 „ 20 60 M 40 80 „ 60 100 .- 80 98 PRINCIPLES OF AGRICULTURE. The late Professor Wilson formed a classification of soils as follows : A, Siliceous^ containing f silica or sand. B, Argillaceous, n | clay or silicate of alumina. C, Calcareous, n J chalk or carhonate of lime. D, Hwniis, II J vegetable matter. A + B = Loam (normal); AAB = Sandy loam ; ABB = Clay loam. B + C = Marl ; ABC = Sandy marl ; BBC = Clay marl. P + A = Light vegetable soil ; DAB == Garden soil. By this classification we learn, for instance, that if we take equal parts of an argillaceous and siliceous soil, we form loam, and that two parts of siliceous and one argillaceous will give us a sandy loam, and if the pro- portions be reversed, a clay loam. The mechanical analysis above described would not determine wdiether the sand contained in the soil consisted of grains of quartz or of limestone ; nor whether the fine earthy particles consisted of vegetable mould (humus), chalk powder, or true clay. Taken, however, in combination with this chemical classification, a fairly accurate descrip- tion of the soil can be given. 184. A loam, it will be noticed, is a soil in which sand and clay are about equal, and a sandy loam, a clay loam, a gravel loam, and a chalk loam, are loams in which these ingredients are predominant. A marl is a clayey soil con- taining from 5 to 20 per cent, of carbonate of lime, and a calcareous soil is the result when over 20 per cent, of lime is present. A sandy soil containing carbonate of lime is called calcarene. All soils may be said to be mixtures of sand, clay, limestone, and humus in varying proportions. A soil is best adapted -for cultivation when it contains the ingredients in the following proportions : Sand, from 50 to 70 per cent. Clay, n 20 to 30 Pulverised limestone, m 5 to 10 m Humus, „ 5 to 10 ,1 CLASSIFICATION OF SOILS. 99 185. Soils are also classified in a rougli and ready manner by the use of various commonplace terms. A clay soil is called heavy, and a sandy soil light. This does not refer to weight, because a cubic foot of sand weighs more than a cubic foot of clay; but to the fact that a clay soil is tenacious and heavy to work, and a sandy soil easy. Clay soils are also called stiff and stubborn, and loamy soils are spoken of as open and free- working. A hungry soil is one which wants a lot of manure and has little power of retaining it ; mellow is a term applied to a soil in a fine state of tilth ; a soil too retentive of water is a cold soil, and a shallow or thin soil is one which has little depth — the distance from the surface to the subsoil is but little. A warm soil is generally a well-drained soil, and is also an early soil, as on it crops grow well and ripen early. A grateful soil is one that gives a good return, and a kindly soil one which can be v»'orked at any time and in any way as desired. A sharp or ready soil is gritty and clears up the plough irons, and a dead soil is one that contains too much vegetable matter. Other terms used are dry and wet, rich and poor, which explain themselves. The differences between light and heavy soils may be tabulated as follows : Light Soils. 1. Dry in character; allowing water to pass freely. 2. Need little drainino-. .3. Warm, loose, and friable. 4. Composed chiefly of silica (sand) and lime. Heavy Soils. 1. Damp in character ; absorbing moisture and retaining it. 2. Much improved, and in need of drainage. ,3. Cold, compact, and close (impervious). 4. Composed chiefly of siUcate of alumina (clay). Questions.— 1. How can yon classify soils? Wliat is the relative value of each system of classification ? 2. Exi)lain the terms Loam, Clay, Marl, Peat. 3. By what popular or vernacular terms are soils called by farmeis, and what do you understand when such terms are applied to soils ? 100 PRINCIPLES OF AGRICULTURE. CHAPTER XXIY. SOME CONSTITUENTS OF SOILS. 186. We have seen that the principal ingredients of soils are sand, clay, carbonate of calcium, and humus, and as each of these preponderates, the soil is said to be sandy, clayey, calcareous, or peaty. We have already considered humus, and have now to learn something about sand, clay, and lime. 187. Sand is composed of pure quartz (silica), and con- sists of very small, hard, clean particles of stone, like exceed- ingly fine gravel. It is loose and easily carried by the -winds, and it cannot retain water, neither will the particles of sand adhere to each other. Pure sand does not contain any plant-food, being simply silicon combined with oxygen. But sands which are termed micaceous, because they con- tain fragments of the glittering mineral mica, can offer some plant-food when the mica is decomposed. A pure sand by itself is of no value to a farmer, except as a con- stituent of other soils, for it tends to make them open and permeable to moisture, air, and warmth, and it raises the temperature of the soil, as the particles of sand easily become warm under the rays of the sun. If a sandy soil contains no clay, it will be unproductive, and we can roughly find the proportions of sand and clay in a soil by mixing some with water, shaking well, and leav- ing it to settle, when the sand, being the heaviest, will sink to the bottom of the vessel, and the clay form a layer on the top. Sand, we have seen, does not retain moisture, and the coarser the sand is, the quicker will water both percolate and evaporate. The incapacity of a sandy soil for retaining water may be shown by pouring measured quantities of water on separate equal measures of sand and clay soils in SOME CONSTITUENTS OF SOILS. 101 fiower-pots. It will be found by the time that water begins to drain away, that the clay will have taken up more water than the sand, in the proportion of 2J to 1 ; and if the pots be placed in a warm room, the water will evaporate more rapidly from the sand than from the clay in the same pro- portion as above. As clay, which we will presently de- scribe, possesses properties exactly opposite to sand, it follows that the most useful agent whicli can be used to improve a sandy soil will be clay ; a clayey soil, sand. Another method of improving a sandy soil is by using humus or vegetable matter, which has a binding action. 188. Clay is simply a hydrated silicate of alumina. It is made up of exceedingly minute particles, which readily adhere together, and possesses a remarkable degree of plas- ticity. It is impermeable to water, and retains moisture. Pure clay, like pure sand, contains no plant-food ; but it is generally more or less impure, and the impurities contain most of the necessary plant constituents, especially potash. Pure clay is a powerful cement, causing the coarser particles of soil to adhere, just as humus acts as a cement on sandy soils ; and these two substances are the principal cementing materials in soils. Humus in a clay soil increases its porosity. The physical properties of clay differ a good deal from sand. Sand is loose and non-cohesive, clay is firm, plastic, and tenacious ; sand rapidly loses moisture, clay is very retentive of it ; sand easily becomes hot and dry, clay remains cool and moist. As a constituent of a soil, clay confers the following properties : It condenses the oxygen of the air, retains moisture, gives tenacity, absorbs and retains plant-food which results from the decomposition of manures, and by its impurities supplies useful sub- stances (alkalies) adapted to afford plants necessary ash ingredients. In a clay soil the fine particles of clay, differing from particles of sand, lie very close together, and thus leave very small spaces through which water can 10^ PRINCIPLES OF AGRICULTURE. percolate very slowly; it is in consequence continually dami^, and therefore cold. When a wet clay soil dries, it shrinks, and forms a solid crust on the surface ; this crust will in time crack, and both expose and injure the roots of plants. A peaty soil acts in the same way when dried up, and the shrinkage in both clay and peat is about one-fifth of their bulk. We have seen that fertile soils can absorb and retain plant-food, and this is one of the features of clay, which €an be demonstrated by experiment. 189. Clay we may consider to be a mixture of extremely fine sand and a small quantity of a colloid body — pure clay or alumina — a voluminous gelatinous substance. When acted on by lime, the cementing material is precipitated as in the following experiment : Mix some clay soil with rain-water, and after subsidence fill two glasses with the turbid liquid ; to one glass add calcium chloride and stir, then note the rapid precipitation and its nature, similar to coagulation. Clay is coagulated by lime,' and the physical characters of a clay soil will differ according to the coagu- lated or uncoagulated state of the clay. One of the im- portant properties which lime possesses is the power of lessening the puddling tendency of clay soils. It coagulates the finely divided particles, and makes the soil more friable, and thus improves its physical character. Heavy land is dressed with lime and chalk, not only to assist in liberating plant-food, but to improve its physical character. 190. Carbonate of calcium or limestone is found in most soils, though not in any large proportion ; but it is beneficial to the soil in many ways. Commonly speaking, it is called 'lime,' but. carbonate of calcium is limestone; and when this is burned it becomes quicklime or caustic lime, which, when mixed with water, becomes hydrated lime, slaked lime, or slack lime. The presence of limestone in a soil can be detected by rubbing some soil down to a powder and pouring on it a few drops of weak hydrochloric SOME CONSTITUENTS OP SOILS. lO^ acid, when it will effervesce. Carbonate of calcium makes clay soils more friable and pervious to water. On account of its reaction with acids it promotes the decomposition of vegetable matter and organic manures, and the formation of nitrates in the soil. It also enables clay to exercise its absorbent power on salts which would otherwise escape and be lost, and is itself a plant-food. A calcareous soil is generally light in colour, and with respect to natural properties, is related to both sand and clay. Its cohesion is greater than that of sand, yet far less than that of clay. It will absorb a great deal of water, but is not impervious like clay ; and it shrinks less than the latter when dried, but is quickly heated and dries much more rapidly. One of the features of Australian soils, especially in Victoria and New South Wales, is the very marked deficiency of lime in their composition. Lime reduces the toughness of clay land, and makes it easier to work and to warm ; if added to a sandy soil in small quantities, it has a beneficial influence, but in large quantities it has an injurious effect. 191. A soil such as we noted in par. 184, as best adapted for the purposes of cultivation, contains enough sand to make it warm and pervious to air and moisture ; enough clay to render it moist, tenacious, and conservative of manures ; enough carbonate of calcium to furnish calcareous material, and to decompose organic matter; and sufficient humus to supply requirements in nitrogen, and assist in maintaining carbonic acid in the interstitial air of the soil. Actually, in nature, soils have one or more of the in- gredients in great excess. The materials, then, which go to form a soil are, we may say, sand, clay, limestone, humus, and mineral fragments (stones). Questions.— 1. Of what is sand composed, and what are its physical properties ? 2. What are the physical properties of clay, and in what do they differ from sand ? 3. What is the physical benefit to be derived from liming clay ? 104 PRINCIPLES OP AGRICULTURE. CHAPTER XXV. SOIL PIIYSICS* 192. Soil composed of sand, clay, lime, and humus is simply a mass of small particles of various sizes, and the size of these particles influences the porosity of the soil, as the larger the particles are, the more space there will be between them, and the soil will therefore be more porous. 193. By specific gravity is meant the relative weight of equal volumes of diff'erent substances — that is, the com- parative weight of bodies having equal bulks. The follow- ing table shows specific gravity of soils and soil constitu- ents, distilled water being taken as I'OOO : Common earth 1*48 Rough sand 1-92 Earth and gravel 2-02 Moist sand 2'05 Gravelly sand 2*07 Clay 2-15 Clay and gravel 2 '48 SiUceous sand 2 -653 Sandy clay 2601 Loamy clay 2 '58 1 Garden mould 2-332 Humus.... 1-370 Limestone 2-64 to 2-72 Quartz 2-56 to 2-75 These substances have the power of retaining heat nearly in proportion to their specific gravity. The density of a soil is of practical importance, and to make land more solid or to get a firm seed-bed, heavy rollers are passed over it, or it is trodden by stock, especially sheep. 194. Soils have a varying capacity for moisture, accord- ing as their physical conditions differ. BOIL PHYSICS. 105 Per cent, of Water ^^' l^^'hl^I^^^' saturation. spread in dry air. JFine quartz sand "25 "88^ Limestone sand '29 76 Heavy clay soil '61 "34^ Clay soil..' '40 -52 Strong loam '51 '45^ Average loam "52 -32 Rich sandy loam -§9 -241 Marl -85 -28 Peat 1-80 -25^ It must be remembered that the nature of tlie subsoil con- siderably influences the action of the surface soil. Thus, a light sand with a retentive clay subsoil will resist dry weather as well as any good soil with a less retentive subsoil. 195. In dry weather, soils lose water by evaporation. In this way a sand will give off the same Aveight of water in one third of the time it would evaporate from a stiff clay, a peat, or a rich mould. The evaporative power of a soil is closely connected with its porosity and temperature. It is always greater on a soil covered with vegetation than on a bare soil, and in open soils than in more compact ones. The presence of stones, surface cultivation, and mulching have been found to diminish the rate of evaporation. Evaporation is least when the surface soil has been broken up by tillage ; summer cultivation will retard it, but com- pressing the land is liable to assist it. Evaporation is most active in spring and summer, and to it we may trace the coldness of land which is saturated or retains a large quantity of water. To show that evaporation cools, we might place a few drops of water on a block of wood, and then stand a small beaker on it. Place a little ether on the beaker and blow over it. The evaporation of the ether will freeze the water. 196. The temperature of a soil materially affects its physical action and the progress of vegetation. The most 106 PRINCIPLES OF AGRICULTURE. important natural source of heat is the sun ; artificial sup- plies are the result of chemical action^ as it is universally true that heat is evolved during chemical combination. A hot-bed and a damp hayrick are examples of heat from chemical action. We kno^y that different substances require different quantities of heat to raise them in tempera- ture to the same extent — that is, each possesses a specific capacity for heat, or specific heat. To illustrate specific heat, take two cylinders of iron and tin, of the same shape and weight. To prepare these, cut off 1^ inch of rod iron, f inch in diameter, make a mould from it in j^laster ; take the same weight of tin as iron, melt it, and pour it into the mould. Attach wire or string to the cylinders so that they can be suspended. Immerse both in boiling water. Take them out simultaneously, and place them on a cake of wax supported by its edges. The wax should be of such thick- ness that the hot iron perforates it and falls through, while the tin remains supported. Water is a substance which has a great specific heat, and where it is present, a rapid eleva- tion of temperature cannot occur in consequence of the great amount of heat which must be absorbed by water before it can show even a moderate increase in warmth. Rnbstanpps Specific Heat of bubstances. ^^^^^^ Weights, Substanops Specific Heat of Iron -1138 Copper *09o] 5 Mercury -0333 Lead -0314 Water............. 1-000 Ice -513 Wood charcoal '241 Silicon -177 Carbon (diamond) '147 Heat is also transferred in three different ways — that is^ by conduction, convection, and radiation. Conduction implies the passage of heat from one particle of matter to another in physical contact with it. Convection is the carrying of heat by particles of matter raised in temperature and set in motion. Radiation is the conveyance of heat from a body through a transparent medium surrounding it. SOIL PHYSICS* 107 197. Dark-coloured soils absorb the greatest amount of heat from the sun's rays and reflect the least, Avhile light-coloured soils absorb the least and reflect the most. Schlibler found that when the thermometer was 77*" in the shade, sand (natural colour) in the sun showed 1121°, black sand 123^"^, and white sand 110°. Dry sands and clays and black garden mould become warmed under the same sun to nearly an equal degree, brownish-red soils somewhat more, and dark peaty soils the most of all. So that the presence of humus, we find, is favour- able to soil warmth, and the oxidation of humus evolves heat. A soil rich in sand will be warmed and cooled more rapidly than a soil containing little sand. This is due to sand being an excellent conductor of heat ; chalkj on the other hand, is a bad conductor. The temperature of a soil is important during germination and the growth of a young plant, for silch plants are more benefited by bottom heat, which is suli heat absorbed by and retained by the soil. Gardeners, when they desire to force on plants, put them on a hot-bed where they will get bottom heat, and soils are early through this heat. Dry soils, again — that is, soils which have not an excess of water — take in more heat from the sun than wet or damp soils, and are from 10° to 15° F. warmer. Water has a very consider- able effect in cooling a soil, partly from its high specific heat, and partly from the immense amount of heat used up during evaporation. The drainage of wet land affects its temperature, giving greater warmth to the soil, and conse- quently an earlier growth. During the night, heat is radiated, and when the temperature falls below dew- point, soils condense water from the atmosphere. Schiibler found that sand will retain its heat for three hours after the sun has gone down ; clay, two hours ; vegetable soil, one hour; but these vegetable soils will all the sooner begin to absorb the dew that falls. In bright sunlight, soil 108 PRINCIPLES OF AGRICULTURE. is much hotter than air. When the temperature of the air in the shade is 60° or 70^ a dry soil may be as warm as 90° or 100°. Soils also become much more heated when exposed to the rays of the sun in a ver- T.. 1 • +1 Tff 1 ^ 4^-1 tical than in a sloping Diagram sliowing the dinerence between vertical ^ *^ rays, confined to smallest space of land surface, direction Fig. 20. and slanting rays, which are more distributed, and consequently Aveaker. (fig. 20). When the sun is at an elevation of 60°, the sun's rays fall on the slope of mountains — raised at an inclination of 30° to the horizon — at a right augle. 198. The situation or aspect of land has an important influence on productiveness, based on the direction or inclination of the sun's rays. Land exposed to the heat of the sun nearly all day would be a suitable situation for stiff, damp soils, but injurious to dry, loose, sandy ones. Land having a westerly aspect is exposed to the sun for a shorter time, and dew remains on the ground longer in the morning. A light and dry soil is well suited for this aspect. Land with a northerly (or, at the antipodes, southerly) aspect is likely to suffer from frost more than the others, and the best soils for this aspect are those rich in organic matter. 199. Climate has also an effect on soils, especially as regards variations in temperature. As an example, we have formed a table, for Melbourne, Victoria; and on the same lines tables can be formed for any locality. Melbourne, it must be remembered, is only 91 feet above sea-level. Meteorological information as illustrated in this table allows us to compare the temperature of surface soil with that of air, and the temperature of the subsoil at various depths. SOIL PHYSICS. 109 AVERAGE TABLE FOR 14 YEARS. -_ . . Spring. Summer. Autumn. Winter. Entire Mean temperature— Sept.-Nov. Dec.-Feb. Mar.-May. June-Aug. Year. Air 57-0° 65-3'' 58T 49-2° 57'6° Surface soil 62-0° 76-5° 61-9° 49-2° 62-4° Soil at 14 inches deep. 53 -9° 652° 58-2° 46-6° 56-0' Soil at 3 feet deep 57-3' 67-6° 63-5° 51 '5° 60-0° Soil at 6 feet deep 57'3° 66-3° 65-0° 55-0° 60-9° Soil at 8 feet deep 56-6° 637° 64-5° 56-6° 60-4° Dewpoint 46 '4° 52 2° 49-1° 42-6° 47-6° Mean rainfall 7*79 in. 6-41 in. 5*78 in. 5*67 in. 25-65 in. (■10-3days.) (24-4 days.) (28-9 days.) (419 days.) (135-5 days.) Mean humidity 70 p. c. 65 p. c. 73 p. c. 79 p. c. 72 p. c. Highest temperature in the shade Ill '2° Lowest M „ „ 27-0° Greatest yearly rainfall recorded in 34 years 44 '25 in. Smallest n „ n 15 '94 in. As we liave chosen an Australian table, it may give us a more comprehensive view of our subject if we note what are the main differences experienced by Australian agriculturists in comparison w^itli their brethren in Europe. They arise from the greater irregularity of seasons and the peculiarities of the rainfall and evapora- tion in Australia. In the first place, the rainfall is heavy in Australia — that is, not that it is an abnormal yearly fall, but that much more falls per hour in Australia, when it rains, than it does in England. Then the heating effect of the sun is much stronger in Australia, and there the soil is not in that general high state of cultivation which Ave find in England, and which by its tilth tends to preserve the moisture in the soil. But the fact of leading importance, as noticed in par. 34, is that in Australia, though the rainfall be abundant, the evaporation is still greater than the rainfall. 200. The physical properties or soil physics which we have been studying can be best summed up in the words of Schiibler's own resume: 'The more an earth weighs, the greater also is its power of retaining heat; the 110 PRINCIPLES OF AGRICULTURE. darker its colour and the smaller its power of retaining water, the more quickly and strongly will it be heated by the sun's rays; the greater its power of containing water, the more has it in general the power also of absorbing moisture when in a dry, and oxygen when in a damp state from the atmosphere, and the slower it usually is to become dry, especially when endued with a high degree of consistency ; lastly, the greater the power of containing water, and the greater the consistency of a soil, the colder and wetter of course will that soil be, as well as the stiffer to work either in a wet or dry state.' 201. Having gone so far into soil physics, it may be just as well to note that the commonly accepted views as to the importance of ca^^illarity, action of lime, and the double silicates, &c., may have to be much modified. The 'soil- germ ' theory, advanced by Messrs Hunter and McAlpine, two Scotch investigators, is that fertility is dependent more on the presence of germs in the soil than on the many physical conditions now considered necessary. Infertility witli them means sterility, as sterilised soils are found to be infertile. They state that the feeding of the desirable soil germs is of as much importance to the agriculturist of to-day !)s is the sowing of seeds and manuring of plants, and assert that manure applied to soils acts not as direct plant- food, but as food for soil bacteria. By this new doctrine a reasonable explanation is afforded as to the cause which makes one soil fertile and another barren, when they both have the same chemical composition and resemble each other. Questions. — 1. What do you undeistand by specific gravity, and wliat is its practical importance? 2. What influence on evaporation has stones, snrface cultivation, looseness of texture, crops, and weeds? 3. What effect on soil temperature has climate, colour, night radiation, evaporation, and draining? 4. What effect has ploughing, hoeing, rolling, and mulching on capillary action, evaporation, soil moisture, and temperature ? in CHEMICAL PROPERTIES OF SOILS. [4. Soil Chemistry. — Describe the histooy and formation of some soil in the neighbourhood — Describe sand, its oHgin and con- stituents ; clay, its origin and constitnents ; calcareous matter, its origin and constituents ; humns, its origin and composition — Point out the general distribution of plant-food among the in- gredients of soil — Effect of ' ivccdhering 'on the inorganic constitu- ents of soil ; disintegrating action of frost, solvent action ofwcdcr containing carbonic and humic acids — Effect of cmtumn tUlage and bare fallow — Effect of vegetation accumulating humus cd the surface — Action of animal life, worms, moles, ants, d:c. in the soil — Differences between surface soil and subsoil. The absorptive or retentive jJOtvcr of soils toivards ammonia, potash, magnesia, lime, and phosphoric acid— Substances for which soil has little or no retentive power — The absorptive action of humus, hydrous silicates, and hy drat cd fern c oxide — Influence of lime in assisting the absorption of bases from salts — Difference in the retentive power of various soils ; importance of this fact as regulating the choice and time of appliccdion of manures. Oxidation of organic matter in soils, action of animcd life, fungi, and bacteria — Final products of oxidation — Origin oj saltpetre and nitrate of soda — The nitrifying bacteria ; in what part of the soil most abundant — The effect on their action of varying conditions of temperature, supply of water and oxygen, and of basic mcdter — Effect of tillage on p>roduction of nitrates — Accumulcdion of nitrates during bare fallow — Influence of manure on the production of nitrates — Solubility of nitrates, their removed into the srdjsoil and into drainage and icell-watcr — Action of crops in talcing up the nitrates in the soil, and in diminishing drainage- Conditions favourable to the dimimdion of the nitrogenous organic matter of the soil — Conditions favourable to the accumulation of nitrogenous organic matter — The root and stubble residue left by various crops — Special effect of laying dow7i land in pasture, and of the cultivation of deeply rooted leguminous crops — Effect of farmyard and other organic maniires. 112 PRINCIPLES OF AGRICULTURE. Show chemical analysis of a soil, if possible one in the district — Mention quantities per cent, of nitrogen, phosphoric acid, potash, lime, and magnesia found in common soils, fertile and infertile ; show their amount in pounds per acre to a depth of nine inches — These constituents mostly insoluble ; practical importance of this fact — Nature of soluble ^natter shown by composition of drainage waters— Action of plant roots upon insoluble inorganic plant-food depends on its condition — Illustrate from ^^uhlished experiments that abundance of nitrogenous matter, phosjyhatcs, andp>otash may exist in a soil, and yet the crop starve for lack of them — Distinc- tion between active and inactive plant-food — The great value of manures supplying food immediately available to the crop ; the fertility thus imparted soon exhausted — Distinction betiveen the permanent fertility of a soil and the condition superinduced by high farming.'] CHAPTEE XXYI. WHAT FROST, WATER, AND AIR DO TO ROCKS. 202. All soils have been produced by the prolonged action of water, air, and frost. Frost generally is the great breaker-np of rocks, and it does this work in the same way that it bursts water-pipes and vessels in which water is kept in the winter. 203. As a general rule, the colder anything becomes, the smaller it gets ; just as the hot iron rim or tire, which the wheelwright puts on the wheel, immediately shrinks when he throws the cold water on it. It is large enough to go on easily when hot ; but after it is cooled, it fits so tightly, that every joint in the wheel is pulled quite closely together. In like manner water gets less in bulk the colder it gets, till it reaches a point of coldness a few degrees above freezing; when, the colder it then gets, the more it increases in bulk, till by the time it becomes ice, it is so much larger, that six pints of water would, when changed into ice, occupy the space of about seven pints. Kow, if it has not the room to swell out in this way, it will WHAT FROST, WATER, AND AIR DO TO ROCKS. 113 burst whatever confines it, and so make room. We do not generally find out the cracks which it makes by thus expanding until the ice thaws ; for while it is in the solid state, it holds the pieces together. 204. In the winter-time many of the cracks and crevices in the rocks get filled with water, and when this freezes, it swells out, and by degrees splits the rocks into large pieces. Besides this, water, either as rain, fog, mist, or snow, soaks a little way into the surface of the rock, particularly if it is not a very hard kind, and when it freezes, pushes the tiny particles of stone apart, and so causes the surface to crumble away. 205. The surfaces of stones, in the walls of old buildings, have been worn away by this same means ; and this is what is meant in the decay of the stones by the loeathering of winter. Clayey ground is often broken up into great rough clods in the autumn, for the frost of the following winter to crumble it for seed-sowing in the spring; and it does it by the method described, much better than man can do it with all his implements. And this is the way in which soils are first formed on the surfaces of rocks, upon which mosses and such-like tiny vegetables grow. These again decay, and so help to improve the new soil for yet higher forms of vegetable life. 206. Air, as we know, consists mostly of a gas named nitrogen; about a quarter as much of another gas called oxygen ; and a very small part of it indeed also consists of a third gas called carbonic acid. But as the nitrogen does not interfere Avith rocks at all, and the oxygen only to a small extent, the carbonic acid gas becomes chief factor. 207. As rain falls through the air, some of the carbonic acid mixes with it, and this enables the rain-water to dissolve some of the surface of a rock just as it would, without the carbonic acid, dissolve sugar. But there are some kinds of rocks which the rain-water can dissolve much H 114 PRINCIPLES OF AGRICULTURE. more easily than others, and these are the rocks which contain the lime that is used to make mortar for building. Limestone, chalk, and marble are of this kind. These rocks consist chiefly of lime and carbonic acid, and for this reason are said to be made of carbonate of lime. When they are burned in the limekilns, the heat drives the carbonic acid gas off into the air, and so the lime — quick- lime as it is now called — only is left. It is this solvent power of rain and mist when they contain carbonic acid which causes marble tombstones to become worn and rough, and which has formed the great limestone caves in different parts of the world. 208. Some of the rain-water dissolves so much of this carbonate of lime from the rocks, that when we get it again from our wells or springs, and boil it, it leaves a coating on the inside of the tea-kettle of carbonate of lime, which often comes off in thin flakes. And in like manner, as this water is warmed or evaporated by the sun on the surface of the ground, it leaves the carbonate of lime behind on the soil. 209. Rain-water, by the aid of the carbonic acid, also dissolves from the surface of rocks some of the potash and soda which they contain ; this leaves the particles of the rocky surface in a less firm condition, and more porous; consequently moisture is easily retained, which with the frost readily crumbles it into, powder. So we see now how water which contains some of the carbonic acid of the air can dissolve all rocks away, and especially those which contain much lime. 210. Running-water slowly wears away the rock over which it travels, and the more particles of rock and soil it carries with it, the more quickly can it grind away the stony surface below. This, as you will see, is a power which streams possess quite independent of the carbonic acid of the air. The scored condition of the sides of the WHAT FROST, WATER, AND AIR DO TO ROCKS. 115 mountain ravines in Wales, Cumberland, and Scotland si lows us that in a former age — the great 'ice-age' — glaciers performed an important work in the removal of rocky frag- ments of all sizes from these mountains to the valleys below. At that period the valleys were under the sea; and the glaciers, as they moved slowly down the ravines, carried with them immense quantities of the rocky fragments which the frost had split off the mountain surfaces. These stones, as they moved along on the ice, scraped the sides of tlie ravines, and when at length that portion of the glacier in which they were embedded reached the sea, they were deposited on the sea-bottom, where they became water- worn. We find these pebbly ' boulder ' stones — now that the sea-bottom is dry land — far removed from their parent mountains, lying in clay or gravel beds. In northern regions — the coast of Norway, for example — similar glacial action is going on to-day. Questions. — 1. What is the origin of soils, and what are the natural agents which are engaged in the work of soil formation ? 2. What effect has rain-water and running-water on a rock? 3. By what means is the crumbling of a rock accomplished ? CHAPTER XXVII. REMOVED SOILS. 211. Soil sometimes remains where it is formed, but in many cases a great deal of it is carried away by rivers, and either laid down again in other places, or carried into the sea. Those soils which are still in the places where they wore first formed may be called stationary soils, and they now cover the rocks of which they were once a part. The white chalk soils which cover the chalk hills of England, and a great deal of the other soils which are to be found in the less hilly and central parts of the 116 PRINCIPLES OP AGRICULTURE. country, are soils of this kind, and consist of the same material as the underlying rocks from which they were made, though they are often a mixture of the different kinds of rocks which adjoin each other. 212. Soils which have been brought away from their native rocks, and laid down in other places, are called transported soils. We shall just notice how this removal takes place. The rain which falls on the mountains and hills, washes the fine soil from the surface of the rocks of which it was made, and runs down the sides in thousands of little streamlets; these join together and form swift torrents, which are able to carry with them bigger pieces of the rock ; these again join together later on, to form a muddy river. Soon the larger and heavier bits of rock fall to the bottom ; and the coarser grains, though carried farther on, sink as the river reaches the plains below, and so the water gets clearer and clearer, till only the very smallest particles of soil are carried by it to its mouth. 213. As the river pursues its course, feeders flow into it on each side, and bring with them soils which they have washed from rocks of perhaps quite a different kind from that from which the river itself started ; and thus the soil carried to the mouth would not only be very fine, but very likely of a mixed character. 214. Very slowly, but each moment of each day and night for hundreds of years, some of this soil is deposited at the mouths of rivers, and large flat tracts of rich clay of a mixed character are gradually formed. These are called alluvial or mud soils.- From what has been said, we would expect to find these alluvial soils along the flat parts of a river's course, and especially at its mouth ; and this is exactly the case. On each side of the Humber, and round the Wash, are exten- sive alluvial districts ; and if we look at a map of the REMOVED SOILS. 117 world, we will notice tliat the land quite juts out into the sea at the mouth of the river Mississippi in North America, the Po in Italy, the Nile, and many others, from the alluvial soils which these rivers deposit at their mouths. The rich flats to be found in Australia and Tasmania are simply alluvial soils deposited by rivers. And again, if we examine a cross-section of any river-basin, we will find that, as we ascend, from the bank of the stream, the texture of the soil gradually becomes coarser, until we encounter a belt of rough, stony land at the foot of the hill. The amount of alluvial deposit carried by rivers can be judged from the fact, that the Ganges colours the sea with mud to the distance of sixty miles from the coast, and the Amazon does the same for 300 miles. 215. We have seen that much of the fine soil is carried into the sea ; there it gradually sinks to the bottom. But this is not always lost; for on some parts of the coast the mud is thrown up by the Avaves and tide, or the sea ceases to cover it, and so we have alluvial soils formed by the sea. Land near the south-east coast of Kent, and coast of Somerset, has been formed in this manner. The sea is both making land and carrying it away. The city of Kavenna, for example, was formerly a seaport of the Adriatic, but now stands over four miles inland. On the other hand, the site of the old town of that fashionable bathing-place, Brighton, has been completely submerged ; and all the site of the ancient little town of Cromer is now part of the bed of the German Ocean. Questions. — 1. Explain the terms 'stationary' soils and * transported ' soils. What stationary soils are different in character to the natural rocks of the district? 2. What are alluvial soils? Why are they generally fertile? 3. Wlierein does a peat -moss differ from ordinary soil? 4. AVJiat chemical substances are present in our soils in large quantities? Also name at least one of those which are generally present only in small quantities. 118 PRINCIPLES OP AGRICULTURE. CHAPTEE XXVIII. FORMATION OF SURFACE SOIL AND SUBSOIL. 216, Soils consist of two parts, one called the top or surface soil, the true soil, which is turned up by the plough, and in Avhich roots of plants exercise their functions; the other is termed the subsoil or under-soil, into which deep roots penetrate to find water, and is immediately below, and merges into the top soil. Generally, subsoils, having less hnmns, are lighter in colour, though there is very little difference in alluvial soils ; but a piebald appearance in ploughed land is a sign of a poor, thin top soil. All soils have originally derived their mineral constituents, directly or indirectly, from the disintegration of rocks. The several rocks, in turn, were fc*4^^,,>,^u,iAu^iki.,^« dissevered into parts and ground into powder of different degrees of fineness by the action of air, water, and weather. Soil is, then, pulverised rock, and subsoil may be regarded as some- thing between the two (fig. 21). These soils, as we have seen, may bo local, sedentary, or indigenous — that is, derived from part of the rocks immediately underneath them, resembling them in composition, and often in colour. They may also be erratic, volcanic, or transported, in which case ICS- Fig. 2L A, uiulerlying rock ; B, subsoil; C, surface soil. FORMATION OF SURFACE SOIL AND SUBSOIL. 119 they have been deposited by various agencies on rocks which may or may not be similar in composition. 217. The various agencies which have been active in transporting soil are chiefly glaciers, rivers, winds, action of the sea, and eruptive action of volcanoes, but both local and erratic soils have been produced from the decay of rocks. The following table shows the various groups of rocks : CLASSIFICATION OF ROCKS ACCORDING TO THEIR MODES OF ORIGIN. — [Fream. ) IGNEOUS- VOLCANIC. feam^jZes— Basalt, and all lavas and trap rocks ; volcanic ash. PLUTONIC. Example— Gx3A\\ie. AQUEOUS— . MECHANICALLY FORMED OR SEDIMENTARY. (a) Argillaceous or Clayey. £xampZes— Mud, clay, loam, shale, marl. (6) Arenaceous or Sandy. ExctmpZes— Sand, silt, sandstone, gravel, rubble, shingle. CHEMICALLY FORMED. Examples— nock-salt, gypsum. ORGANICALLY FORMED, (a) BY ANIMALS. I. Calcareous. Examples— Shell-marl, coral-rock, chalk, oolites, mag- nesian limestone. — ii. Siliceous. Examples — Diatom-earth, flint. —III. Phosphatic. Examples— Gt\x3i.\\o, phosphatic nodules and beds (coprolites). (&) BY PLANTS.— IV. Carbonaceous. Examples— Fe&t, lignite, coal.— V. Ferruginous. Examples— Bog-\vo\\ ore, clay ironstone. METAMORPHIC— ExcwipZes— Crystalline limestone (marble), dolomite, clay-slate. Igneous rocks have been cooled down from a molten condition, and are un stratified ; they do not contain fossils, and are crystalline in structure, like granite. Aqueous rocks are usually stratified — that is, arranged in beds or layers, and have been built up under water. They are usually granular in texture, and contain remains of animals and plants (fossils) — sandstones and limestones, for example. A metamorphic rock is one that belongs to neither of these two classes, but is an aqueous rock that has been subjected to great heat and pressure. A volcanic rock is like lava, the eruption of molten rock matter ejected by ■volcanoes. 120 PRINCIPLES OP AGRICULTURE. 218. The decay of rocks is called weathering, and is the result of four sets of agents. First, tlie mecliariical agencies, which produce disintegration ; then the chemical agencies, which decompose the rocks ; next, the thermometrical agents, heat and cold ; and lastly, animal agencies, such as earthworms, moles, and rabbits. 219. The power of disintegration may be seen in (1) the action of a glacier, which crushes the underlying rock and carries the pieces of crushed rock (detritus) with it as it moves along, depositing this detritus a considerable distance away. (2) The action of running-water, accompanied by the frictional action of rolling stones and sand downwards, lays bare the surface (denudes) along which it flows, and carries away at the same time the material loosened. Alluvial soil is formed by the deposition of the material which is carried in suspension. Eiver- valleys have been scooped out in this way. (3ther agencies may be recognised (3) in ocean currents, and action of waves and tides on the coast-line ; in action (4) of wind itself ; and in the action (5) of rain-drops, whicli we recognise by saying that it will wear away the hardest stone. The agency of the M'ind can be seen in such countries as South Africa and Australia, where the hot winds make the air seem as if dense with smoke, due to dust which is so fine as to get through seams and cracks where water does not enter. 220. The chemical action which decomposes is due (1) to the oxygen in the air, which combines with substances in rocks ; these become oxidised, and the oxides formed are carried away, dissolved in water, and by this means the solid texture is changed, and the rocks begin to crumble and fall away. The action of air is seen active in summer when soils and rocks are wet or dry alternately. Another force is the solvent power of rain-water. (2) Few substances c:ui resist water, especially when it has potash or soda FORMATION OF SURFACE SOIL AND SUBSOIL. 121 in solution, as wo see daily by our use of soap. The power of rain to disintegrate is aided by dews, fogs, thunder-showers, snows, and frost. Perhaps the greatest force is carbonic acid (3), which increases the solvent power of water, and which rain obtains from the atmosphere while falling, and from the humus in the soil. It is through carbonic acid that water carries away matter in solution. When water is said to be 'liard,' this is because it con- tains carbonate of lime ; and when it contains sulphate of lime, we say it has acquired permanent hardness. Humus is a source of carbonic acid, and soils rich in organic matter are bound to contain an interstitial atmosphere of carbonic acid. Rain-water absorljs it, and also humic acid, then acts as a solvent; and we thus have the organic matter reacting on the inorganic. The air enclosed in the pores of the soil is poorer in oxygen than the ordinary air, but mucli richer in carbonic acid. Soil that has not been dis- turbed for a year or so has been found to be 22 to 23 times richer in carbonic acid than the air, and a soil eight days after manuring was found to contain 246 times as much. This is due to the evolution of carbonic acid by decaying vegetable and organic matter in the soil. PROPORTION OF AIR AND CARBONIC ACID IN SOILS UNDER DIFFERENT CONDITIONS OF CULTURE. Kind of Soil. Culture. Carbonic Acid. Oxygen. Heavy clay Artichokes 0-66 19*99 Fertile moist Meadow 1-79 19-41 Sandy unmanured Asparagus 1 '54 18 '80 Sandy „ None 974 10-35 The juices which plant roots exude have also a dissolving effect, and may be considered as another (4) chemical agent. 221. The thermometrical agents are frost and heat — the two extremes, and what we might call the weather 122 PEINCIPLES OP AGRICULTURE. influences. The action of frost has been noted; and as regards heat, when the sun beats on a rock, the constituents of the rock have different powers of absorbing heat, and expanding and contracting as they are heated and cooled, and this inequality acts as a factor in breaking them np. The actions of heat and cold are the most silent and recurrent of all the forces. The animal agencies, especially earth- worms, act more in further allowing the forces which act on rock to continue their action on the loose materials formed, and Avhich we term soil. The weathering agents which act on rocks still act on soils, so that they may be in a position to support plant-life. 222. Geological knowledge has really a practical value for a farmer, because, though there are hundreds of different beds known to geologists in all parts of the world, they have an unvarying place in the series of rocks and soils produced from a group of these rocks. ]S^o matter in what part of the world they are found, they have a definite likeness. Both the mixed soils from any given group or segregation of rocks, and the uniform soils from any one species or class of rock, are originally the same in all parts of the world ; for so long as rocks of any one kind, or class, or grouping occur as sources of either detritus or alluvium, no matter where, their constituents are always the same, and must necessarily yield by disintegration the same sort of frag- ments and powder. An agricultural geologist, if informed as to the formation on which a soil rests, and from which it is derived, and knowing the nature of the climate, can give a very fair opinion on the agricultural value of the soil, though it may be in Canada or Australia. Skill in local farming in Europe is a hinderance to a farmer in the colonies unless to it he has added a knowledge of the principles, grounded on a broad and wide view of the processes and requirements of agriculture in the world. FORMATION OF SURFACE SOIL AND SUBSOIL. 123 Questions. — 1. Explain why frost and changes of temperature pulverise soils. 2. Explain the origin of alluvial and peaty soils. Are stones useful in soils? If so, how? 3. Why is the texture or mechanical condition of soils and subsoils of equal importance with their chemical composition? 4. Describe the way in which our different kinds of soils are formed. 5. Explain and give illustrations of the efiect of atmospheric agencies in the soil. State the chemical agencies which favour the formation of soils, and show how the same results are promoted by chemical agencies. 6. To what is the action of disintegration due ? How does humus improve the natural rock-formed soil ? CHAPTER XXIX. SOIL CHEMISTRY. 223. Sand in soils owes its origin to the decomposition of granitic rocks, and clay to the result of the decomposi- tion of felspar, and in the mineral fragments in the soil this change is undergone by exposure under tillage. The more frequently they are exposed, the more rapidly do they crumble away. The chemical effects of tillage is to yield new supplies of inorganic plant-food. It also promotes the process of nitrification, making the vegetable matter decom- pose readily ; and by making the soil finer, it allows air to get access to every particle, and permits the absorption of ammonia, nitric acid, and watery vapour from the air. The effect of autumn tillage is to expose the insoluble ingredi- ents in the soil to weathering, so that when sown down in spring, available plant-food will have been prepared ; and the difi'erence between active and inactive plant-food is that the active is in a soluble form, and can be availed of by a plant, while the inactive is insoluble and unavailable. Bare fallow, which means rest from growing crops and being weathered, also tends to accumulate plant-food in the 124 PRINCIPLES OF AGRICULTURE. soil, but bare fallowing can be . only tliorouglily successful in a dry climate. In a wet climate it results in a rapid diminution of soil nitrogen, and to check this waste, farmers grow ' fallow crops ' and ' catch crops ' in a climate like the British. At Rothamsted experimental station, two and a half times as much nitrogen was washed out from the bare soil as from soil upon which wheat was grown. In a dry climate bare fallowings assist in the production of nitrates, and increase the fertility of the soil. The efi'ect of vegetation, we have seen, is the accumulation of humus at the surface of the soil ; and the decay of the organic matter leads, through the carbonic acid gas evolved, and solvent power of M'ater, to further stores of plant-food being pre- pared. 224. We have seen that under a bare fallow, soils lose nitrates quickly, and it is one of the salts which are not retained by any soil ; for example, the well-known manure, nitrate of soda, is not retained by soils. Soils differ in their capacity of retaining fertilising materials, and seem unable to hold either nitrates or the clilorides and sulphates of calcium and sodium ; drainage waters also remove calcium carbonate. These are the substances for which soil has little or no retentive power. On the other hand, there are certain substances retained in large quantities. Way found that, as a rule, it was the base and not the acid of a salt which was absorbed, and, according to Kullenberg, the order in which they are taken up is as follows : Ammonia, potash, magnesia, lime, soda, the phosphates and car- bonates of bases being the salts absorbed in greatest quan- tities. The theory of the absorptive power in soils is that it is due to the presence of hydrous silicates, hydrated ferric oxide, and humus. Way's theory is that in the soil there are double silicates — aluminium silicate combined with calcium silicate, &c. If potash be brought into contact with this, it will take the place of cal- SOIL CHEMISTRY. 125 cium, as it has a greater affinity for it than for lime. Aluminium silicate combines most readily with am- monium, and least with sodium. Some chemists state tliat the absorptive powder for ammonia is due to the hydrated ferric oxide usually present in a soil, and Warington claims great absorptive powers for ferric oxide (red oxide of iron). This has a decided action on the manure ' superphosphate,' as the soluble phosphate is rendered insoluble by the action of lime, iron, and alumina. Humus also absorbs manure apparently in the same manner that charcoal takes up colouring matter. It has been found that the application of lime in a caustic state to a soil assists in the absorption of the bases from salts present in soils. It breaks up the double silicates by which potash, soda, and ammonia are liberated, and it also decomposes saline compounds of iron, manganese, and alumina, which form naturally in the soil. Loams are about the best absorbents of manures. In a soil containing clay only traces of ammonia, potash, or phosphoric acid are ever found in drainage waters. Sands, on the other hand, have smaller retentive power, and are dependent on immediate supplies of plant-food. 225. No soil has a capacity for absorbing unlimited quantities of manurial matters ; for example, if a solution of ammonium phosphate be passed for some time through a quantity of soil, it will at first be retained, but after a time the solution will pass through the soil unchanged. We should bear in mind this fact, and the difference in the retentive power of various soils, as regulating the choice and time of application of manures. On light, open soils of little retentive power, manures that are only slightly soluble should be used. Heavier soils, whose retentive power is greater, are best able to retain soluble manures. Then, in a wet climate, an insoluble manure will act more speedily than in a dry one. Soluble manures, again, are 126 PRINCIPLES OF AGRICULTURE. best applied to the soil in spring, so that a vigorous grow- ing crop can use them up ; and, on the other hand, an insoluble or slow-acting manure should be applied in autumn, so that it might have time to decompose by the season a crop is ready to make use of them. As phosphatic and potash manures are retained by the soil, they can be applied just as it suits the farmer's con- venience. 226. We have so far been studying the mineral con- stituents of the soil, but the chemistry of the organic elements is also interesting, and is a matter of great im- portance. The organic portion of ordinary soils is formed by the decay of vegetable matter, and is the great source of natural nitrogen supply to the plant. The material from which this nitrogen is obtained contains a large pro- portion of carbon, and these materials are oxidised by worms, fungi, bacteria, &c. The two chief factors are earthworms and bacteria. The earthworms feed upon the organic matter in the soil, and to get sufficient food, pass a large quantity of earth through their bodies, which they eject as castings on the surface. The humic acid generated in the worm, acts on the soil, and their action assists in the oxidation of the soil. Bacteria or micro-organisms are a class of agents that have only been recognised within recent years. Some decompose organic matter, either by giving off oxygen or by reducing organic substances to carbon dioxide and water ; others take awny oxygen from bodies, while the most important elaborate the nitrogenous matter of humus, which for plant-food is unavailable, into nitric acid, which is available. In hot countries nitrates are found in the soil, potassium nitrate in India, and sodium nitrate in Chili and south-west coast of South America. The nitre soils in Bengal are the sites of old villages^ and the saltpetre is found as an excrescence on the surface of the soil. In hot weather the evaporation from the surface SOIL CHEMISTRY. 127 causes the water charged with saline matter to ascend to the surface, which, when it rises in vapour, is left behind ; thus w^e see in many parts of Peru and India, during the dry season, the country whitened over with different saline substances. When rain falls, this saline crust is dissolved and descends, and in dry weather it ascends. This action in dry weather explains why the surface soil of any field contains a larger proportion of soluble inorganic matter in the middle of the hot and dry season than in any other. We may add that any soil in a warm, dry country is more absorbent of moisture, has a freer internal circulation, and makes richer accumulations of salts and organic remains than the same soil in a cold, wet country. 227. The nitrifying bacteria are found in abundance in the surface soil, and the depth to which the action may descend depends on the porosity of the soil. Two of these micro-organisms have been isolated ; the one effects the conversion of ammonia into nitrites, the other into nitrates. Nitrification goes on or acts more quickly under circum- stances favourable for rapid growth, and in this respect is parallel to germination. The conditions under which they develop are the presence of (1) food constituents, especially phosphoric acid ; the presence of a base with which the nitric acid formed can combine, usually fulfilled by car- bonate of lime ; and a plentiful supply of oxygen. A further condition is the presence of a sufficient quantity of moisture. The action of nitrification stops at low tem- peratures under 12'' C. or during frost, nor does it take place at a temperature above 55° C. (131° F.), and it dies at 90° C. The action is best at a temperature of 37° C. (99° F.), or blood-heat. Further, the action is stopped by the presence of plant poisons in the soil ; and strong sun- light wn"ll also check it, as it seems to go on best in dark- ness. Nitrification takes place chiefly in the first 12 inches of soil, but Warington states it may take place at a depth 128 PRINCIPLES OF AGRICULTURE. of six feet. Tillage operations have a distinct influence in promoting nitrification, so that we may say it goes on best in well-drained, properly tilled soils, not poor in lime or other necessary mineral ingredients. Peat soils are the richest in nitrogen ; and sandy soils, and soils deficient in organic matter, the poorest. The following table shows the amount of nitrogen found in an arable and a pasture soU. at varying depths : NITROGEN IN ROTHAMSTED SOILS AT VARIOUS DEPTHS. Arable Soil. Old Pasture Soil. Depth. Per Cent. lb. per Acre, Per Cent. lb. per Acre. First 9 inches 0-120 3015 0-245 5351 Second ., .. 0-068 1629 082 2313 Third .. 0059 1461 0-053 1580 Fourth.. .. 0-051 1228 0*046 1412 Fifth .. .. 0-045 1090 0042 1301 Sixth ., „ 044 1131 0-039 1186 The production and accumulation of nitrates is probably^ as already noted, the most important result of a bare fallow, In ordinary farm soils at Rothamsted left as a bare fallow^ 35 to 55 lb. of nitrogen per acre has been found at the end of the summer. 228. Every shower that falls tends to wash the nitrates downwards, and we find that, owing to the great solubility of the nitrates, they are washed down into the subsoil, the drainage waters, and the wells. The solubility of nitrates can be tested and shown by placing some powdered garden soil on a filter and pouring upon it a little water. To the filtrate (that which passes through) add a few drops of diphenylamine in sulphuric acid, and then very gradually and cautiously some -oil of vitriol. A dark-blue colour shows that nitrates are present in the solution. A mass of soil at Rothamsted has lost by drainage from 28 to 47 lb. of nitrogen as nitrates per acre per annum, and the mean annual amount of nitrogen per acre lost in drainage over a period of thirteen years was 37 lb. Experiments have SOIL CHEMISTRY. 129 shown that the loss of soluble salts from the soil takes place most when the percolation of water is rapid, so that a heavy rainfall in a few days does more harm than the same rainfall distributed over a month. AMOUNT OF DRAINAGE AND NITRATES IN DRAINAGE WATER FROM UNMANURED BARE SOIL, DRAIN GAUGES 20 TO 60 INCHES DEEP : AVERAGE OF THIRTEEN YEARS. Amount of Nitrates. Drainage. Per million of Water. Per Acre. 20" 60" 20" 60" 20" 60" Rainfall, inches. gauge, inches. gauge, inches. gauge. gauge. gauge, lb. gauge, lb. March- June. .. 902 0-85 0-94 7-3 8-9 1-41 1-89 July-Sept.... .. 8-24 2-49 2-20 15-6 130 8-81 6-44 Oct. -Feb ..12-95 9-81 9-55 10-2 10-4 22-57 22-47 Whole Year... 30-21 1545 1505 10-7 105 3729 35-64 Questions.— 1. Explain how the character of tlie suhsoil affects the fertility of soils. 2. What are the advantages arising from autumn cultivation ? Describe also the advantages arising from a frequent supply of fresh air to tlie soil. 3. On what soils and under what circumstances would you recommend bare fallow- ing ? 4. Wliy are clay soils usually rich ? What are the causes of barrenness in sandy and peaty soils? 5. Why is the period of ' rest ' or fallow conducive to the fertility of soils ? 6. Write a description of a fertile soil under the following heads : (1) Its chemical composition ; (2) its texture, including that of the sub- soil ; (3) its surroundings. 7. What are the sources of the supply of nitrogen to the plant, and in what way is it supplied to the soil, and how removed therefrom ? 8. Under what conditions can nitrification be carried on ? For what substances have soils little retentive power, and what is the theory of the absorptive power of soils ? CHAPTEK XXX. soil chemistry — continued. 229. We have seen that as drainage becomes active, nitrates, which are easily washed out, are taken from the I 130 PRINCIPLES OF AGRICULTURE. soil, and a serious loss of valuable plant-food occurs. Now, how can this be checked ? Mainly by the action of crops, as we know that the evaporation of water from a growing crop keeps the land dry, and that evaporation is greater on land under crop than from a bare soil. The growing crop keeps the nitrates nearer the surface, and roots constantly take them up for plant-food. The loss of nitrates by drain- age is far less when the land is under crop than in the case of a bare fallow. Cropped land gives off more moisture than it would if left in bare fallow. At Rothamsted it was found that a crop of barley removed from the soil in the same time more water — equal to a rainfall of 9 inches — than was evaporated from an adjoining bare fallow. 230. In the natural vegetation of a forest or prairie, or any unfilled ' virgin ' land or pasture, we have the condi- tions favourable to the accumulation of nitrogenous organic matter. The elements taken from the soil are returned to it by the decay of the plants which it has nourished ; under these circumstances the surface soil becomes rich in carbon and nitrogen, and also in the ash constituents, collected by the roots from the under-soil, and left at the surface by the decay of the plant. The nitrogenous organic matter of arable land is maintained when the supply from crop residues and organic manures equal the amount that has been used up or lost. When virgin land is brought under the plough, the accumulation of nitrogenous organic matter in the soil begins to diminish, because oxidation is most active in soils under cultivation, and in arable land we get the maximum production of plant food and waste by drainage. Further, the produce of the land does not decay on it, but is taken off and consumed elsewhere. 231. The portion of plants left in and on a soil after harvest has important functions, as it is the main source of SOIL CHEMISTRY. 131 humus, and consequently of the nitrogen of the soil. The amount of roots left practically determine the amount of humus obtainable. Turnips and potatoes have few roots, and the residue is the leaves left uneaten by stock. Cereal crops leave a considerable residue, but poor in nitrogen. Deep-rooted crops, such as clover or lucerne, which draw their nitrogen from the air, are the best for nitrogenous humus. Permanent pasture shows that, compared with arable land, it has twice as much nitrogen and more than twice as much carbon. We may say that the heavier the crop, the greater is the residue, so that good crops will enrich the soil with nitrogenous humus, while bad crops will diminish it. The following in- dicates some of the figures obtained regarding crop residues : KESIDUES OF CROPS. Pounds per Acre. ReSo. Nitrogen. ^^^^^^^^'^^ Potash. Good clover-roots 6503 65 -0 27 '0 Timothy grass-roots 2240 31-1 V'O 8-4 Oats, roots, and stubble.. 2200 25*0 28 24-0 232. We have seen that pasture-land accumulates humus, and the special effect of laying land down in pasture is to increase the amount of nitrogen in the soil. The same object is attained by growing deep-rooted leguminous crops. In pasture-land the loss of nitric acid by drainage is small, as the soil is covered by vegetation, and the accumulated nitrogen will be chiefly in the form of grass roots, stems, and humus. At Eothamsted, arable land laid down to grass gained nitrogen during thirty-three years at the rate of about 52 pounds per acre per annum. Legu- minous plants, we have already seen, have the special power of acquiring nitrogen from the air by means of their root tubercles, so that they always enrich 132 PRINCIPLES OF AGRICULTURE. the ground ^vith nitrogen, so much so that it is the most important means a farmer has for giving nitrogen to arable land. Practice pointed this out long before the value of root tubercles was known, when it was recognised by farmers that wheat grew best after a crop of clover. The leguminous crops must be considered as remarkable nitrogen gatherers, when we find that a crop of red clover can be cut and removed off the soil, thus creating, as we would expect, a deficiency in organic nitrogen ; yet, never- theless, the surface soil, owing to the residue of roots and stubble, is left actually richer in nitrogen than it was before. What makes this special power in leguminous crops more puzzling, is the fact that nitrogenous manures generally produce little effect on them. 233. We can also increase the proportion of humus in a soil by adding farmyard and other organic manures. Green manuring — that is, ploughing up green crops, is another way of giving to the soil a large amount of humus, and is especially effective for light sandy soils, and barren soils in hot climates. Farmyard manure assists also in the physical condition of the soil ; but besides the organic matter which it adds to the soil, it has all the constituents plants require, some available at once, but the greater part slowly available. Organia manures not only give bulk to the soil, but supply it with nitrogen. 234. We will now go back to the inorganic materials in a soil. The following two analyses show the composition of a fertile and infertile soil. It must always be borne in mind that there arc many factors besides chemical composi- tion which will make a soil infertile. Some soils that are infertile, when drained become fertile ; improve the physical conditions as to capillarity and evaporation of others, and they also become fertile. SOIL CHEMISTRY. 133 EXAMPLES OF CHEMICAL ANALYSES. Fertile Soil. Barren Soil. 1. Organic matter 13-550 0*260 2. Soluble in moderately strong hydrochloric acid 7*190 0-458 Insoluble matter 79-260 99282 100 000 100-000 1. Organic matter containing nitrogen 0-460 0025 2. Above soluble matter contains the following : Phosphoric anhydride 0-250 0*008 Sulphuric anhydride 0-140 0015 Carbonic dioxide 0-120 0038 Chlorine 0-040 0-014 Potassic oxide 0-160 0-011 Calcic oxide 0*170 0*094 Magnesia oxide 0*530 0-046 Iron, sodic, and aluminic oxides 5-780 0*232 7-190 0*458 235. We must remember that though we get a certain percentage of substances soluble in water and acids, we cannot by this means measure vegetative force, Avhich is perhaps equal to weak solutions of acetic acid ; and then we cannot calculate the vital force or the selective power which plants possess. Further, the portion which we find soluble is in nature always changing by alterations of temperature, action of farmyard dung, lime, moisture, carbonic acid, &c., either increasing or decreasing. The fact of practical importance to a farmer is, that the con- stituents in the soil are mostly insoluble, so much so that it may be said that 99*8 per cent, is insoluble and about 0*2 per cent, soluble, so that if this 0-2 per cent, be exhausted, the available fertility of the land is gone, and it ceases to be remunerative. 236. The value of chemical analysis is that it indicates 134 PRINCIPLES OF AGRICULTURE. the potential fertility of a soil, which must not be mistaken for the actual fertility. But chemical analysis has estabhshed one or two points which must be borne in mind. (1) If a soil has all the necessary physical properties, the mere presence of organic and inorganic plant-food will not be sufficient to produce a crop ; but this food must be present in such a quantity, at the proper season, within easy access to its roots, and within the time allotted for its natural growth, for it to obtain the supplies it wants without any difficulty. Another point (2) is that if a soil is particularly poor in food substances, crops can be grown, but not in such a manner as to yield remunerative returns ; and further (3), the same thing may be said to take place when soils contain some substances in too great abundance. The three substances which apparently rule a soil's fertility are nitrogen, phosphoric acid, and potash. Phosphoric acid is generally about one-tenth per cent., and potash varies from a trace to several per cent. But the question for a farmer is — in what condition are these two most important mineral in- gredients? The phosphoric acid is almost entirely in a condition insoluble in water, and the potash is soluble only from 001 to 009 per cent. It must be therefore clearly understood that though a soil contains abund- ance of fertilising matter, only a trifling amount is in an available form, and this accounts for the marked action of artificial manures. The ingredients in these manures are in a quickly available condition, and suit- able for the immediate wants of the plant. We can learn the nature of the soluble matter in the soil by looking at the analysis of drainage waters, bearing in mind that drainage water contains not only the natural soluble ingredients of the soil, but the soluble ingredients of manures which have not been retained either by the plant or soil. SOIL CHEMISTRY. 135 COMPOSITION OF DRAINAGE WxiTER ACCORDING TO ZOLLER. Manured iMciniired iiuu^ii ciay rvuuyii ciay , . li'iiifi Knil wif.li snil wit.li snil wnfliniit; ot water contain A million rmrU Manured Rough clay Rough clay ' ., Manured ^ "LlKn lii'ie soil with soil with soil without Z^L^^l clay soil with )t water contain .-egetatiou. vegetation, vegetation. ^J^^^XV vegetation. Solid matters... 472-32 254-64 292-64 305-20 291-50 Ash therein 317-62 176-74 196-78 214-50 212-16 Potash 6-50 2-37 203 5-46 3*82 Soda 7-11 5-60 7-43 23-74 6-02 Lime 145-86 57-60 70-80 68-41 92-34 Magnesia 20-52 8-80 0-32 2-93 5-12 Ferric oxide 1-32 6-35 8-26 5-76 4-30 Chlorine 57-49 9-52 20 87 39-46 35-27 Phosphoric acid 2*23 Sulphuric acid.. 17-47 27*13 27-82 29-30 33-49 Silica 10-46 1135 17-46 9-50 936 237. We have seen that soils have a large store of possible food, but that 0*2 is only doled out, and this is its fertility; and accordingly as this percentage varies, a soil may have a low or high natural fertility. A farmer, by the use of manures, and by the processes of working, can add additional fertility or condition to the soil. With high farming the contributions to the soil may be in excess of requirements, and its acquired fertility may consequently increase. The acquired fertility of a soil may be taken away, and the natural fertility of a soil can be reduced, but the experi- ments of Sir J. B. Lawes, and Sir J. H. Gilbert, at Rotliamsted, prove that soils have a permanent fertility which cannot be taken away. After a continuous growth of wheat for a period of fifty years, on the same soil, without any manure, instead of the soil being now absolutely barren, it yields about ten bushels per aero. This permanent fertility of soil is only an abstract question ; the fertility the farmer looks for is one that will commercially repay him for time, labour, and capital expended. When working with virgin land, he is using up a store of acquired fertility. This, by continuous cropping, is soon reduced to the natural fertility 136 PRINCIPLES OF AGRICULTURE. of the soil. Then by still cropping, without giving some- thing back, the balance of natural fertility is upset, and the soil begins to go back to its permanent stage. The question, then, is a commercial one — will the returns now received pay ? The answer is, that for all practical purposes, the soil is infertile. 238. We have seen that by adding manures with readily available plant-food, we can add to the fertility of a soil ; but this fertility so easily acquired is as easily exhausted. Most soluble and active manures produce their principal effect at once, and, as a rule, farmers top-dress with them, so that the rain may dissolve and carry them down to the roots. Heavy rain occasions much loss, as they are carried then beyond the reach of the plant. Questions. — 1. What do you understand by the dormant constituents of soils ? 2. Why are phosphates so largely used as manures? In a district having a heavy rainfall, is there any form of phosphate to be preferred ? 3. Wliat effect lias tillage operations on a soil, and does it improve any soil ? Does it render them more productive ? If so, how ? 4. Can you explain how it is that a soil may contain large stores of plant-food, and yet such a soil may not be fertile? 5. Upon what does the degree of fertility or sterility of a soil depend ? 6. What is the difference between permanent and acquired fertility? What substances rule a soil's fertility, and in what conditions are the mineral substances in a soil ? 7. What are the conditions favour- able to the accumulation and diminution of nitrogenous organic matter in a soil ? 8. What is the special effect of laying down land to pasture, and cultivating deeply-rooted leguminous crops ? 137 CULTIVATION AND IMPROVEMENT OF SOILS. [5. Tillage. — Implements, and effect of tillage— Describe the ordinary plough, cultivator, harrow, and roller, and point out the special action of each — The importance of tilth — Recapitulate the effect of tillage operations on the water, heat, weathering and oxidation of the soil, and show how the special mode of tillage can be altered to meet varying requirements.] CHAPTER XXX L CULTIVATION A MEANS OF ENRICHING LAND. 239. We may have often seen the ploughman at work in the fields, steadily going backward and forward from one Fig. 22. — Eansomes' 'Steel chill' Plough, with patent divided share. end to the other, and turning over the soil in long straight furrows. And if we were asked, ' "Why does he so cut it up and turn it overf we would probably say, 'For the same 138 PRINCIPLES OF AGRICULTURE. reason that people dig their gardens — namely, to make tlie ground soft, and so prepare it for seed-sowing, and for the growth of the crop afterwards.' And this answer is quite right as far as it goes. But the question is lioic does this in any way prepare the ground to receive the seed, and improve it for the healthy growth of a crop? 240. We know, from what has already been said about the formation of soils from rocks, that rain-water, by the help of the carbonic acid gas which it has absorbed from the air, actually dissolves out of the rock some of the materials of which it is composed. And this action will go on much more quickly among the countless number of tiny rocky particles of ready-made soil than on the surface of a mass of rock. We have also seen in a former lesson that the roots of plants can only feed on those substances in the soil which are soluble in rain-water and in the juice of root-hairs. 241. Now, when land has been thoroughly broken up by the plough or spade, fresh rain-water can the more easily soak into it, and do its work of changing insoluble matter in the soil into soluble plant-food, and of dissolving all that is already soluble. The insoluble matter is often called dormant plant-food. The word dormant means * sleeping,' and it is so called because while it is in this state it is unable to do its work of feeding the plant. When it is changed into tlic soluble form, it is said to be in the active condition. Of course this work will not go on so well, if the water cannot gradually soak through the soil ; hence, as already remarked, land should be well under-drained by means of pipes, if the water will not pass through it naturally. 242. But when it is thus broken up and made soft, air gets into it easily as well as rain-water ; and the oxygen gas of the air, by combining with some of those substances which act as plant poisons, changes their injurious character, CULTIVATION — A MEANS OP ENRICHING LAND. 139 sweetens the soil, and makes it more healthy. And the plough, by turning the nnder-soil to the top, exposes just the very portion of the soil to the air which was out of its reach before. 243. And this is not all the oxygen of the air does ; for it helps the vegetable or organic matter of the soil, as it is termed, to decay or rot away. Now when organic matter decays, some part of it becomes changed into carbonic acid ; this is absorbed by the moisture in the soil, and thus the water gets a supply of this gas from the soil as well as from the air, for its work of rendering the dormant mineral matter active. The following table shows the proportion of carbonic acid gas extracted from the earth at the depth of 4 feet 11 inches by Wolny. PROPORTION IN VOLUME OF CARBONIC ACID IN 100 VOLUMES OF GAS EXTRACTED FROM THE EARTH AT A DEPTH OF 4 FEET 11 INCHES. Month. Carbonic Acid. Temperature. January 3'84 41-9° F. February 4-10 39*9 ., March 3-84 39-5 „ April 4-49 45-1 .. May 5-77 46*2 .. June 6-66 51-7 .. July 8-93 56-5 .. August 10-33 57-5 .. September 10-12 58-3 .. October 9-35 56-3 -. November 7-85 50-9 v December 4-92 47*6 ., 244. But in addition to carbonic acid, decaying organic matter yields other substances upon which plants feed ; and the most valuable of these is ammonia gas, which is also readily absorbed by water. The air, too, contains just a very small proportion of ammonia ; and freshly-ploughed land freoLuently absorbs some of it as it floats over its 140 PRINCIPLES OF AGRICULTURE. surface ; and as a little of it goes a long way as food, and is, at the same time, very expensive to buy as a manure, even a very small quantity is worth catching in this way. Land becomes enriched with plant-food by being turned over and broken up, so that the rain and air may the more easily get into it, to work upon the particles of mineral and vegetable matter of which it consists. But this is only one of the many purposes that the farmer has in view in break- ing up his land. 245. Darwin furnishes some wonderful facts in his interesting book on the work of the earthworm, which he calls * nature's plough.' He calculates that about 20 ounces of half-decayed vegetable matter — which is the chief food of the earthworm — passes through the body of each worm in a year, which, with the particles of the softer rocks, gets ground into a fine condition in its gizzard. At the same time, organic acids are formed from the further decay of this leafy food while thus undergoing digestion, which imparts to the water of the soil even a greater solvent power than carbonic acid does. In many parts of England, more than 10 tons of earth in this very fine condition thus pass through the bodies of earth- worms in a year on an acre of land. And this for the most part is brought to the surface ; so that every few years the whole of the surface soil passes through their bodies. But further, the closing up of old worm-holes and boring of new ones keeps the soil in constant motion, and provides numberless channels for the drainage of water from the surface soil. After this, who will look with contempt upon the humble earthworm 1 Compared with the English earthworms, those found in Australia are simply giants; and in Australia and India another agency as active is ants, which by their underground passages and their hills, CULTIVATION — A MEANS OF ENRICHING LAND, 141 sometimes very large, act in tlie same manner as earth- worms. Questions. — 1. How can cultivation enrich land? 2. At what season of the year is the proiDortion of carbonic acid greatest in the soil ? 3. Why do we turn over the undersoil in ploughing ? CHAPTER XXXIT. cultivation A MEANS OF CLEANING THE LAND. 246. There is nothing that gives a farmer or a gardener SO much trouble as weeds. We know well enough that almost any soil will produce weeds, whether it be rich or poor, and a good farmer will be ashamed to have his land covered with weeds. Weeds are plants out of their place when land is tilled for profit. But the disgrace of being an untidy farmer is not the worst past of the matter; for we must remember that weeds are as much plants as wheat or turnips, and there- fore they require the same kinds of food from the soil; and as they are always the plants best suited to the soil upon which they grow, they draw from it a greater amount of plant-food than those agricultural plants that may not be quite so well adapted for that particular soil, or of so hardy a nature. Weeds must therefore be looked upon as robbers. They rob the crops of their food, and the farmer of his money, for it is his crops that he turns into money. This points to the importance of keeping land clean. 247. But it is not easy to keep large fields free from weeds, and especially of those kinds which, like couch-grass, rapidly spread in all directions underground, where their growth is not so plainly seen. If a field is well cleaned, and the crop gets a good start before the young weeds begin 142 PRINCIPLES OF AGRICULTURE. to groAV, they will not flourish very well, because the stronger searching roots of the crop take most of the food, and leave little for the weeds. But if the weeds are allowed to take the lead, the crop will sadly suffer. Take, for example, the famous fodder crop called lucerne ; it is in its nature and appearance between the clover and the vetch plant. When a field is sown with this, it must be very thoroughly cleaned beforehand, and kept so for a year, that is, until the young plants have gained strength ; after this it needs no cleaning for years, because it grows so strong, and its roots search so thoroughly for food, that weeds cannot live at all with it. And this is true of all those crops whose roots spread rapidly, and are of a searching character; and also in a certain degree, of all crops. Strong growing crops clean land by smothering the weeds. - 248. Now, the way in which farmers clean their land is ivtHiiiiiisi Fig. 23.— Howard's Harrow (iron). by ploughing it up, and breaking the lumps by means of the harrow and roller-; in this way the roots of the weeds are brought to the surface, and separated from the soil to which they firmly clung before. The tines or teeth of the harrow or cultivator then comb them out, and they are either gathered into heaps and burned, or killed by the heat of the summer sun. CULTIVATION— A MEANS OF CLEANING THE LAND. 143 240. Spring-time and summer are tlie times when tins work must be done, before the seeds of the weeds liave been produced and ripened. If weeds are allowed to remain till they have shed their seed, the farmer will find his work of cleaning immensely increased for the following year. Good farmers generally give each portion of the land a thorough spring and summer's cleaning once ^jg, 24.-Wooden Harrow, in four years ; and also check the growth of weeds at other times when they have the oppor- tunity, by means of the horse and hand hoe. Questions. — 1. How is a regular system of cleaning the land usually carried out, and why is it necessary ? 2. Why is land tilled? Give reasons for your statements. 3. What are weeds ? Could wheat or oats ever be regarded as weeds ? CHAPTEE XXXII I. CULTIVATION — A TREPARATION FOR SEED. 250. We shall again simply describe a seed, in order that what it requires during its early period of groAvth may be the more clearly understood. Each seed contains the embryo of the future plant in its centre, called the germ, and this germ has enough food all around it to supply its wants until it has thrown out its first small leaves and roots. When this food is exhausted, the plant has to depend upon the i-oots for the several kinds of food Avhich they suck up from the soil ; and upon the leaves, for the carbon which they absorb from the air. 251. The growth that the germ makes from the supply of food which it has around it in the seed, is, we know, 144 PRINCIPLES OF AGRICULTURE. called germination. Xow, germination, we are aware, cannot proceed without both air and moisture; because oxygen gas and water must soak into the seed to dissolve the plant-food in the seed, so that it may be absorbed by the germ to make it grow. The oxygen renders the food soluble, and the water dissolves it. Warmth is also essential to germination. Schribaux has pointed out a fact worth noting. Wheat, for example, which has been raised in Algeria or France, germinates completely at the end of two to five days. The same varieties raised in England take three to four weeks to germinate. This is due, he says, to the fact that seeds grown in a maritime climate are always more or less humid, and it is precisely the high rate of moisture in the seed which paralyses the production of diastase, and delays germination. In a moist climate, drying seeds before sowing is recommended. 252. Again, the little roots have very fine hairs near their ends — too fine to be seen with the naked eye ; and it is these microscopic hairs that absorb the food from the soil. But in order to do their work, they must come into Kg. 25.— Horse-roller. very close contact with the fine moist particles of the soil. 253. The leaves, too, can only absorb the food, which they get from the air, under the influence of sunlight. Hence it is necessary that seed should be sown near the CULTIVATION — A PREPARATION FOR SEED. 145 surface of fine moist soil, in order that all these conditions may be satisfied. 254. If the soil has only been broken into rough hard lumps, much of the seed may drop down between the lumps, and be buried too deep for either the air to get to it, or the light to reach its first tiny leaves. Or the lumps may be too hard for the tender roots and leaves to push their way through. Or ngain, the root-hairs may not have a sufficient quantity of fine moist particles sur- rounding and touching them from which to draw nourish- ment. And so the seed may remain unproductive and perish. 255. Thus we see the great importance of getting a good tilth or fine seed-bed for the seed. And tliis is obtained by careful cultivation. On light and loamy soils, this can be obtained with no great difficulty by one or more ploughings, rollings, and harrowings. After the seed is sown in these friable — crumbly — soils, it is rolled again Fig. 2G. — Coleman's Cultivator. to press the mould closely round the seed, and to prevent the moisture being dried up as quickly as it would if the soil were left in a loose condition. Some say rolling hastens soil-drying, J 146 PRINCIPLES OF AGRICULTURE. But on a clay soil it is no easy matter to get a fine tilth ; for after the ground has been broken np by the plough, either the lumps, if dry, are too hard to be properly crushed by rolling; or else, if wet, only press tightly together into a mass. The reason Avliy turnip-growing is difficult on clay land is that the small seed requires a finer tilth than can be easily obtained on such land. 256. Stiff soils should be broken up roughly before winter sets in, and then the frost will ciumble the lumps down to a good tilth by spring. The ground can then be stirred by a cultivator, also called a grubber, which will loosen the soil and draw out the couch-grass, without burying the fine soil as a plough would do. The cultivator is an implement M'ith several rows of curved tines pointing forwards, and they can be set to loosen the land at as great a depth as the plough. Like the plough, it can be dragged by either horses or steam-engines, but it is very much harder work for horses than plougliing. Fig. 27. — Tcimant's Grubber. During the dry summer-time, clay is sometimes placed in large heaps and burned slowly by means of dried turf and fagots. It is in this way reduced to powder, and entirely loses its plastic character. AVhen mixed with the clay soil, this powder tends to improve its texture. 357. The objects of cultivating the soil are; (1) To CULTIVATION A PREPARATION FOR SEED. 147 allow icater to percolate through the soil. For all ordinary waters contain dissolved matters (as carbonic acid gas, oxygen, &c.), which act powerfully in converting dormant (or insoluble) matters into useful plant-food. (2) To admit air, whose action is very similar to that of water. (3) To break up and finely divide the soil, so that rootlets can l)enetrate it freely ; while it also then furnishes a good seed-bed. (4) To get rid of weeds, and to expose injurious hisect-life to the beaks of birds. 258. The conditions of successful germination are : To give the seed (1) moisture to dissolve the albumen or plant- food stored up within the seed for the first nourishment of the young plant ; (2) a gentle warmth (best between 80° and 90° F.) ; and (3) the presence of oxygen (from the air) to assist in the chemical changes which take place. The changes which ensue on germination are both visible and invisible. The visible changes are the swelling of the seed, the bursting of its skin or integument, the appearance of the radicle or young root, which grows downward ; while the plumule or young stem grows upward. Either one or two seed-leaves (cotyledons) are also seen, but these soon wither away. The invisible or chemical changes are due to the inter- action of the water and the oxygen with the store of (at lirst insoluble) plant-food laid up in the seed. By the action of extremely small quantities of various ferments (especially diastase), this insoluble matter is changed into soluble substances ; the starch and the ffit or oil is con- verted into dextrin and into sugar, and these (with the gluten or soluble albuminous matter) are absorbed by and assist in the nourishment of the embryo or young plant. 259. Knowing the conditions favourable for germination, we can then secure the conditions necessary for a good seed-bed, and they are as follows i 148 PRINCIPLES OF AGRICULTURE. (1) The soil must be broken up and turned over so as to expose as large a surface as possible to the action of the weather. Wind, sun, rain, and frost will then do their work — (a) reducing the clods, to line powder or tilth which the rootlets can easily penetrate ; and (b) converting dor- mant into active plant-food. (2) The seed-bed must be deem or free from weeds. (3) The seed-bed should be moist, or at least the plants growing in it should be able to abstract moisture from the deeper soil and subsoil — a result which can be secured (as a result of capillary action) by deep ploughing and loosen- ing of the soil and subsoil. (4) The seed-bed must be compact, so that the rootlets shall come into close contact with the particles of earth from which they are to abstract the plant-food. Questions.— 1. What effect has climate on seeds as to their germinating power? 2. What visible and invisible changes ensue on germination? 3. With what object do we cultivate or work a soil ? 4. What are the conditions necessary for a goo. These implements are used more for thinning out plants than cleaning the land. 312. When seed has been sown by the drill distributor, one of the advantages gained is tliat the land can be kept clean by cultivating between the rows. The horse-hoe works between the drills of corn, as shown in fig. 84. The most approved arrangements of the hoe blades to suit the con^ ditions of various crops and systems of cultivation are shown in fig. 85. 313. For root- crops grown in drills the imple- ment used in Scot- land (fig. 8G) is a type of drill scuffler, or drill harrow, and in England the horse- hoe employed is shown in fig. 87. Here the upright arms are dispensed with, and a cast-iron skim, turned up at the sides, substituted. The most important feature in this hoe is the application, of a tine harrow after cutters, which deposits the weeds, &c. on the top of tlie ground, and at the same time adapts itself to any inequality of the surface. 314. The inventor of the drill and father of the horse- hoeing husbandry was Jethro Tull. His main principle was that tillage will supply the place of manure. He argued that time and the tillage expended on the spaces between Fig. 84. — Garrett & Sons' Lever Horse-hoe. IMPLEMENTS FOR INTERCULTURE. 189 the plants were quite sufficient to supply all the available mineral matter and nitrates needed, and that the roots of plants had the power to gather this food. iJ ^j:i ^ For ; Wheat. For Beans and Peas. For Turnips or Mangel-wurzel. Fig. 85. 315. Adaptations of the Tullian system have been attempted by Wilkins of Wix and the Rev. Mr Smith of Lois Weedon. The Lois Weedon system is crop and Fig. 8G.— Sellar & Son's Scotch Drill Scuffler. fallow alternating in the same field. The difference in the Tullian and Lois Weedon systems is that in the former ploughs and horse-hoes are nsed, in the latter, spades and forks. Forking up the soil gives a better tilth. The diagram (fig. 88) shows the difference between the 190 PRINCIPLES OF AGRICULTURE. ordinary and Lois Weedon systems. At Lois Weedon, under this system, excellent crops of wheat were grown without manure in the same field for nearly twenty years. The wheat was in triple rows, one foot apart in the rows, with intervals of three feet. The in- tervals were dug two spits deep before winter, Fig. 87. -S. Corbett & Son's English Horse-hoe or Turnip Scuffler. scarified in spring, and forked through the summer ; this stirring being found to feed the corn-plants growing on each side, as well as prepare a fine and fertile seed-bed An ordinary and TuUian crop of Wheat, 12 inches apart in the rows. A Lois Weedon crop of Wheat, in triple rows, 12 inches apart in tlie rows, with 'intervals of three feet. Fig. 88. for the rows of wheat the following year. The wheat- rows and fallow-intervals succeeded each other alternately, the same strip being thus bare-fallowed every other year. The system is now abandoned. IMPLEMENTS FOR INTERCULTURE. 191 Questions. — l. What is the action of the horse-hoe? For what purpose is it used? 2. AVhat do you understand by tlie Lois Weedon system of cropping? 3. On what principles was ti\e horse-hoeing husbandry of Jethro Tull based ? CHAPTER XL. EXHAUSTION AND IMPROVEMENT OF SOILS. 316. Crops, as we know, are grown to feed people and animals ; and are themselves fed from the soil and air. Now, if every particle of animals and i^lants were given back again to the soil, it would then, on the whole, not only contain as much plant-food at one time as at another, but w^ouLl even become richer, because some substances which had been first of all obtained from, the air would afterwards be returned to the soil. But w^e know this is not the case, for animal productions, in the forms of milk, meat, wool, and hides, are being regularly carried away from the land where they were produced, to supply our shops with human food and clothing, and only to a small extent find their way back again to the fields. 317. And much the same may be said of many of the most valuable vegetable productions — the grain of wheat, barley, and oats, as well as fruits of all kinds. It is true the farmer takes care of the dung from the cattle, and such waste vegetable substances as straw, and returns them to the land again ; and this prevents it becoming poor as quickly as it otherwise would. Then, too, the loss may be largely supplied by a portion of the insoluble plant-food in the soil becoming soluble ; and in this way soils may yield good crops for many years together. But even then, in course of time, the soil must get gradually poorer ; for year after year it gives away from icitliiu much more than it receives back again from loitliout. 192 PRINCIPLES OF AGRICULTURE. The following table has been drawn up by Messrs Law^es & Gilbert : Illustration of the proportion of the constituents of crops groavn in rotation at once sold off the farm, and of those retained upon it for further use. Per Cent, of Total in the Crop At once sold off Retained on the Fann the Farm. for further use. Dry Matter 30-6 69*4 Nitrogen 43'6 66-6 Total Mineral Matter (ash) . . 14 '5 85-5 Phosphoric Acid 56'2 43*8 Potash 20-0 80-0 * Referring to the figures/ Messrs Lawes & Gilbert write, *the question arises, to what beneficial or profitable pur- poses are about two-thirds of the total vegetable substance grown — more than half its nitrogen, nearly half its phos- phoric acid, and about four-fifths of its- potash retained on the farm ? Briefly stated, it is for the feeding of animals for the 2^'oduction of meat, milk, arid manure, and for the exercise of force — tliat is, for their labour.^ We thus see that a certain proportion of the constituents of crops is lost directly, and even the proportion retained is also lost when the meat and milk produced is sold. 318. So, if we were asked, 'What is the reason why people manure their land?' w^e might reply, 'To give back to the soil the plant-food wdiich some crop had previously taken out, that it may have plenty for the next.' And it has been shown that a farmer, by being careful of all his waste vegetable substances and the dung of his live-stock, will get enough manure to keep his land good, as long as the land can itself supply, little by little, some food to his crops also. But a time will come when his farmyard manure alone will not be sufficient to keep up the fertility ; and he will then have to supply the deficiency by buying artificial manures. By a wise use of these, not only can EXHAUSTION AND IMPROVEMENT OF SOILS. 193 the fertility of tlie soil be kept up, but soils naturally poor may be rendered very fruitful. A soil is said to be ' poor ' when it contains an inadequate supply of active or soluble plant-food. We know that plants require some nine or ten different substances as food. Now these must all be present in the soil ; and they must all be in a condition in which they can be dissolved by water. For all mineral matter (from the soil) enters the rootlets of plants in the form of a solution. A soil is said to be ' worked out ' or ' exhausted ' when its store of soluble plant-food has been removed by the continuous growth of crops upon it, without any adequate return of fertilising substances or manures. When we say that a soil is 'exhausted,' we mean that in spite of the land having been well and carefully tilled, the crops present a weak and sickly appearance, so that the yield derived is very small. This condition of the soil may arise from a variety of causes. Thus it may be that one kind of crop has been continually grown on tlie same soil, without the food materials which the successive crops have each year taken from the soil having been added or returned to it in the form of manure. The soil is then deficient of that particular food material or materials essential to the proper growth of the special crop grown. * Other crops, however, do not necessarily require this one food material ; but perhaps need another one which was left in the soil by the first crop grown on it. Such different crops would then grow and flourish on the land ; but after a time the soil would be deprived of this second food material also, and on the principle already stated a third variety of crops would have to be grown on the land, till finally the soil is deprived of all its stock of soluble plant-food. No amount of ploughing, &c. would fit the soil for another batch of crops, and the soil would then be said to have been ' com- pletely exhausted,' but complete exhaustion is impossible, M 194 PRINCIPLES OF AGRICULTURE. Another reason why soil becomes exhausted is that the land may be naturally so poor that, although every means is taken by tilling to render the dormant constituents of the soil active, yet these are so deficient in quantity that they are readily used up by the crops in a few years' time. 319. If, however, poor soils are to be made more fertile, the cause of their poverty must first be known. In our chapter on fertile and barren soils, we learned that some of the causes of their poverty or infertility were wetness, sour- ness, coldness, and want of fresh air and fresh rain-water. Now, each of these faults may be set riglit by good under- drainage — that is, by laying lines of pipes underground : they will carry away the water that is spoiling the land, and keep the surface soil from being constantly in a soaked and sour condition. Fresh rain-water will then soak through it, instead of running off the surface, and will carry with it warmth, and gases that will improve the soil ; as it soaks down, too, fresh air will follow it, and sweeten and enrich the soil, as well as help the seeds to grow ; and the sun's heat, instead of being all used up in drying the land, will be absorbed by it, and so make it warm enough for more rapid plant-growth. 320. Corn-fields may often be seen ploughed in narrow raised furrows, so as to form gutters for the water, that the water may be carried more readily off ; and it will be noticed that in such fields the young corn looks yellow and sickly in the hollow parts, while on the top of each furrow it look's a much healthier green. This yellow appearance of either grass or corn is generally due to a wet soil. In winter, too, undrained land will frequently have a heavy mist hanging over it ; and snow will lie unmelted on it longer than on the warmer drained land. Wet land ploughs up in a glossy, soapy state — unlike the more crumbly condition of well-drained soil. Then, again, wet meadows produce rushes, sedges, and marsh grasses, instead of the better kinds EXHAUSTION AND IMPROVEMENT OF SOILS. 195 of meadow grasses and clovers. These are all signs to the fanner that he must improve his land by under-draining. 321. Another thing we learned in the chapter referred to, ■was, that each kind of plant-food must be present in the soil in a state of solution, and also in a form that will gradually become soluble. And to provide plants with these foods is the very object that the farmer has in view when he manures his land. The farmyard manure, Avhich is chiefly made up of the dung of farm animals, and straw in a rotten state, contains all the substances that plants require from the soil, both in a soluble and insoluble form — the phosphorus, the potash, the nitrogen, as well as the other less costly ones. 322. We have also seen that a soil must not contain substances that are poisonous to plants ; and in order to render harmless these organic acids, and other substances that have been spoken of as plant poisons, the farmer has to apply lime, just in the same condition as it is used in making mortar. There is generally enough lime present in soils for the needs of plants as food simply ; but sometimes he has to supply lime as a plant-food to such soils as peat soils, that contain very little of it in their natural state. For this purpose, unburnt lime in the form of chalk will do. 323. Growing plants, which are taken off the soil and the constituents not returned, are, we have seen, a way in which the soil is exhausted. But another source of loss is the ingred- ients carried away by drainage waters, washed out of the soil. 324. On the other hand, there are some sources of gain to the soiL (1) By working the land there is a slow conver- sion of subsoil into soil, and a conversion by natural agencies of unavailable matter into the available state. (2) Then rain falling on the ground carries doAvn substances from the atmosphere. These substances are either held mechanically, as dust and soot, or dissolved in the rain, as chlorides, sul- phates, and nitrates of sodium, calcium, and ammonium. 196 PRINCIPLES OF AGRICULTURE. Tables A, B, and C show first the average composition of rain-water falling in town and country, and the amount of certain constituents found at Kothamsted in rain-water, dew, and hoar-frost. The valuable substances added to the soil are ammonia and nitric acid. Analyses of rain-water made at nine different places in Europe, between 1865 and 1880, gave an average of 10-23 lb. of nitrogen per acre per annum brought down in the rainfall. Another source of gain (3) is the remains of plants in the soil, and (4) the manures, natural and artificial, which have been applied. Table A.— Average composition of samples of rain from VARIOUS districts OF ENGLAND AND SCOTLAND, IN PARTS per million. — {Fream. ) Nitrogen of Chlorine. Sulphuric Acid. Ammonia. Nitric Acid. England, country places, inland u towns 0-88 4-25 0-61 0-44 315 7-49 0-19 0-22 0-11 0-08 0-30 0-63 3-88 8-46 12-24 3-28 5-70 8-72 5-52 34-27 Scotlantl,country places, sea-coast „ .1 II inland... II towns 5-64 2-06 16-50 11 Glasf^'ow 70-19 Table B.— The maximum, minimum, and mean amounts of certain constituents in sixty-nine samples of rain- WATER, IN PARTS PER MILLION.— (i^rmWi.) ll H3 ^1 Nitrogen as i .2^ 1 £ < ll II 'A i Highest proportion Lowest proportion 85-8 6-2 3-72 0-21 0-66 0-03 1-28 0-04 0-44 0-01 1-94 0-13 16-5 0-0 160 0-0 Mean, 69 samples. 33-1 0-90 0-19 0-37 014* 0-70 31 4-7 The mean of 34 samples. EXHAUSTION AND IMPROVEMENT OF SOILS. 19' Table C— The maximum, minimum, and mean amounts of CERTAIN constituents IN SEVEN SAMPLES OF DEW AND HOAR-FROST, IN PARTS PER MILLION.— (/'>ertW4. ) i ii 1 3| o Nitrogen as 6 o .2 i: .2 5 5 11 5 ll Highest proportion Lowest proportion 80 26-4 4-50 l-9o 1-96 0-26 2-31 107 0-50 0-28 4-55 1-66 8-0 3-5 5-3 25 130 Mean, 7 samples.. 48-7 2-64 0-76 1-63 0-40* 2-79 19-0 Questions. — 1. What do you understand by soil exhaustion ? How can it be brought about? 2. What are the sources of gain to the soil ? 3. Under what circumstances would you prefer the cultivator to the plough? 4. How is it that an active cultiva- tion of the soil enriches the land, and thus becomes a substitute for manure ? CHAPTER XLT. CLAYING AND SANDING, PARING AND BURNING, MARLING, WARPING, ETC. 325. Soils that have to be improved may be arranged into two classes. (1) Those which contuin an abundant supply of plant- food.. These are susceptible of improvement chiefly by mechanical methods. (2) Those which are deficient in some available ingred- ient. These can be improved chiefly by chemical means along with mechanical methods. 326. Subsoiling, deep ploughing, and trenching all open up the soil, and therefore make it more accessible to natural agencies, and give plant roots a wider collecting * The mean of four analyses. 198 PRINCIPLES OF AGRICULTURE. field or area. The effect of deep ploughing and siibsoiling is shown best on stiff clay lands, and its value is fully realised when the land has been freed from superfluous water. 327. Soils are also improved by mixing — that is, to clay adding sand, sanding; and to sand clay, claying. Sand added to clay opens the pores of clay and makes it more permeable to the air. Clay, when added to sandy or peaty soils, consolidates and gives them body, and also mixes with them certain earthy and saline substances. It acts best in those soils deficient in the mechanical properties of clay. 328. Paring and burning is sometimes a form by which certain soils are improved. Stiff clays, or very foul and dirty lands, are the most suitable for this purpose. The surface is pared off and the sods are raked or harrowed up into heaps and slowly burned. The advantages of paring and burning are that from the ash the soil gets a valu- able top-dressing, the eggs and young of insects are killed, and weeds and seeds of weeds destroyed ; further, the soil being in a fine powdery state, it is able to absorb ammonia from the air. The ash ought to be black or dark brown in colour — not red. The drawback is the loss of organic matter and organic nitrogen compounds. For this reason, it is not an operation that will improve light soils of a sandy or gravelly nature. 329. Clay-burning is an operation found useful on very stiff, tenacious, and intractable clays, cultivated with diffi- culty and at considerable cost. In clay-burning, the tillage soil is removed and the stiff under-clay dug out and built up into heaps with refuse coal and w^ood, as in the process of charcoal-making. The clay is roasted at a dull red heat, accomplislied by keeping the air out as in charcoal-burning, and it is an operation that takes some weeks. This burnt clay will not resume its plastic character when moistened, and when mixed with the soil makes it loose, friable, and CLAYING AND SANDING, ETC. lOd easily worked ; but it also has a chemical action. The amount of soluble potash is increased, and any phosphates it may contain are rendered more available. The fertility of burnt clays is seen on beans, peas, potatoes, and the turnip tribe ; but a good deal depends on the original composition of tlic clay and the degree to which it has been burned. If it has been overheated, and there is a large amount of lime present — lime acts as a flux — it will bake into bricks or coarse glass, insoluble and unfit for anything but road- making. Voelcker found that in moderately burnt clay soluble potash was increased from 0*269 to 0*941 per cent., but in clay burnt at a high heat it was only 0*544 per cent. 330. Another form of improving land is l^y marling or the spreading of marl, a name given to clays containing variable quantities of carbonate of lime, and valuable for the lime and phosphates they contain. Marls are of different kinds : we have chalk marls, clay marls, shelly marls, slate or stone marls, an inferior variety coloured by iron, bog or peaty marls, and sandy marls, which are the poorest in character. Marl is put on for its lime, and shows best on land deficient in this constituent ; but on sandy soils, clay marls especially increase their coherence and water-holding capacity. 331. By warping is meant the covering of land by water- borne sediment, matter held in suspension. It is practised on tidal-river banks, usually on the flat borders near the mouths of sluggish rivers. It is simply running muddy water on to a flat surface and allowing it to stand still until the sediment settles, then slowly running the water off (fig. 89). The warp makes a rich top-dressing for the land, and in one way may be considered as an alluvial soil. The annual overflow of the Nile is warping also on a large scale. Dry warping is a tenu used to express the improvement of land by top-dressing it with a layer of alluvial soil, which has been carried and spread on it. 200 PRINCIPLES OF AGRICULTURE. 332. When a soil is deficient in organic matter, a simple way of improving it is by green manuring — that is, the seed of a quick-growing crop, such as mustard or vetches, is sown, and when it has attained a convenient height, just before flowering, it is ploughed into the ground. Thus Fig. 89. A, A, earth walls; B, B, fresh water coming down the river, is daniiiied up by the tide C ; D, flood-gate through which the water is run on to the land ; E, E, channels to assist in running off the water at sluice-gate F ; G, section of sluice-gate ; the boards are taken off one by one as the sediment deposits, and the water thus run off the land. all that was taken from the soil is directly returned, plus a large quantity of carbonaceous matter obtained from the air. 333. Other methods of improving soils by the agency of vegetation are meadowing, pasturing, and planting. Land laid down in grass is in some degree rested or recruited, and the longer it lies the greater the benefit. The im- provement takes place by the gradual accumulation of a layer of vegetable matter. This leads through the roots and residue in pasture to an increase in the percentage of nitrogen in the soil, and also of earthy and saline sub- stances. The physical condition of the soil also changes. CLAYING AND SANDING, ETC. 201 Boils at first unfit for arable culture have been also im- proved by tree-planting, and the action is twofold : (1) Trees cause vegetable matter to accumulate on the surface ; and (2) bring up from beneath substances important for plant-life, but in which the upper soil may have been originally deficient. Questions. —1. AVhat is meant by wet warping ? 2. For what purpose is clay-burning performed? Describe the operation. 3. What do you understand by mixing and marling? CHAPTER XLII. DRAINAGE. 334. As the drainage of land is so necessary for the healthy and . successful growth of crops, we will, in this chapter, endeavour to show how the removal of water from the land is carried out by under-drain- age. Just look at tlie diagram (tig. 90). It represents a field that is being drained. You will notice that lines of pipes are laid down in trenches, and these all lead into a main drain, which is in- tended to carry the water that is drained from the whole field into the nearest ditch or brook, and thence into f, f, furrow drains; M, the nearest river. If the field were a • '"''^'" '^''^'^ ^^''^^ "^^^''' deeper. narrow one, the parallel drains might all be made to run across the field into a ditch at once, instead of first discharging their water into a main drain ; tliis, however, is not a good plan, as the excessive number of openings increase the risk of obstruction by weeds, &c. On the other hand, if the field Avere a very large one, mor'e than one main drain might be necessary. 202 PRINCIPLES OF AGRICULTURE. 335. Tlie pipes are about a foot long ; and the hole in the small ones which are laid in the parallel drains is from 2 to 3| inches across ; while the hole in tlie pipes of the main drain is about double the diameter of the smaller pipes. 336. The parallel drains in very stiff clay soils should not be more than 5 yards apart, and about a yard deep ; while, in free-working soils, tliey may be as much as 8 yards apart, and a foot deeper. The main drains should be 3 inches deeper than the others. In laying the pipes, it is very important that a proper fall be given to them, so that the water and sediment or earth may not have the chance to stand and collect ; but this is not absolutely essential unless in level land. The fall should be about 1 inch in every 6 yards. It will be noticed in the diagram that the parallel drains on the opposite sides of the main drain do not enter it at the same points nor at right angles ; and this is to j^revent a collection of earth, or weakening of the main drain, in these places. 337. Many are unable to understand how water which soaked straight down over a whole field could be collected in the lines of pipes which were placed so far apart. The fact is, tlie water does not go down into the j)ipes at all, but rises up into them, entering mostly at the joints. Let us just follow the course of the rain. First of. all, we will suppose there has been a long, soaking rain in the autumn — the beginning of the wet season ; this gradually sinks straight down into the soil, more and more follows it all through the winter, and it sinks farther and farther down, much below the level of the drain-pipes, scarcely any going nenr them. At last it comes to a bed of clay, or some close substance, through which it cannot soak. Having at last come to a standstill, it thoroughly soaks the soil which lies on this impervious bed. More DRAINAGE. 203 Water continues to sink down, and the pores of tlie soil get filled with it higher and higher, till it rises to the level of the drains. Now they begin their work of keeping the water down to this level. They will keep running as long as the land is in a thoroughly soaked condition above them. 338. If we placed a cask on its end, with the bung-hole half-way up, and poured water in from the top, directly it was full to the bung-hole it would begin to run out ; and if we filled faster than the hole carried it away, the water would continue to run out of it after we had done pouring, till it was lowered to the level of the bottom of the bung- hole. This is exactly what takes place in the soil. We must look upon the impervious deep subsoil as the bottom of the barrel, the drains as the bung-hole, and the soil above as the part of the barrel above the bung-hole. 339. It sometimes happens that a clay field lying below the level of an adjoining gravelly or sandy bank or hill, is rendered too wet for cultivation by the overflow of a E C T I o N CLAC SUBSOIL Fig. 91. spring at a point where the two soils adjoin. In such a case, the clay field would be much better and much more cheaply drained by a single drain cut in the clay near the gravel bank, than by a scries of parallel drains. We shall readily understand the reason of this by looking carefully at the diagram of Elkington's System (fig. 91). 204 PRINCIPLES OP AGRICULTURE. The rain which falls on tlie gravel readily sinks down to the clay subsoil ; and as more and more sinks down, the water-level rises to the level of the adjoining clay, and there bursts out as a spring and overflows the field. Now, if a deep hole be dug near where the clay and gravel meet, it taps the saturated gravel below the level of the surface soil, and the water rises into it and is carried away by the drain, as long as the gravel is saturated above the level of the bottom of the hole. This drain is called a ia}) drain. The systems of drainage will be noted in detail in the next chapter. 340. The general advantages of drainage, natural or artificial, are as follows : (1) The temperature of soil and climate is improved, for so long as the sun's rays, required to warm the land, are expended on evaporating surplus water, the land is kept cold, and there is a waste of heat. (2) The temperature of the plant rises. When there is much water present in the soil, the food of plants is so diluted that a much greater quantity of fluid must be taken, so as to obtain essential food requirements. The presence, then, of so much water in stem and leaves keeps down their natural heat. (3) The mechanical and physical condition of the soil is improved. Pipeclay, when dry, can be naturally re- duced to a fine powder, and this is the action in a drained clay soil. When wet, it is close, compact, and adhesive ; remove the water, and it gradually contracts and cracks, and thus becomes open, friable, and mellow. (4) Air is admitted and sucked into the soil. Drains, by removing water, make room for the space to be filled by air, and as the water sinks and trickles away, it will suck the air in after it. The presence of air assists in the disintegration of mineral matter and the decomposition of organic matter. DRAINAGE. 205 (5) It improves soils that burn up in dry weather. How this is brought about is very simple. If ah be the surface of the soil, and cd the level of the waterlogged soil, then plant roots will penetrate as far as cd but no farther, as stagnant water is unwholesome. In a dry season. a- c d e / roots having little depth are burned up and the plant in- jured, by the rise of noxious substances into the upper layers by the force of surface evaporation and capillarity. By a drain, lower the level of stagnant water to e/, and the noxious substances will be washed out, and in times of drought the roots can go in search of water. (6) It prevents the formation of iron pans, as the rains sink through into the drains and gradually wash out the iron in the soil, which would otherwise have sunk to a lower level and formed into a solid cake. (7) It removes noxious matters from the soil. When a crop comes up strong and healthy, then begins to droop and wither, and at last completely dies aw^ay, these facts indicate the presence of noxious matters in the subsoil, which will be removed by drainage carrying away water containing them, and allowing air to enter and sweeten the soil. (8) It removes efflorescences of saline substances from the surface. In undrained soil the surplus water is re- moved by evaporation, and these saline incrustations follow; but a drained soil does not need to evaporate water as an outlet, so such efflorescences are prevented. Questions. —1. What .are the general advantages of drainage? 2. Explain how water gets into drainpipes, and why it does not escape into the soil after once heinj? admitted. 8. How does the drainaj?e from minor drains enter the main drain ? 206 PRINCIPLES OF AGRICULTURE. .CHAPTER XLIII DRAINAGE SYSTEMS AND METHODS. 341. The economical advantages of draining soils are chiefly these : (1) Heavy and stiff soils are more easily worked, and at less expense. (2) Lime and manures are more effective and go further. (3) Seed time and liarvest are earlier and surer. (4) Crops are larger or heavier, and finer in quality. (5) Good nutritive grasses grow in place of inferior ones. (6) Wheat and turnips can be grown on land where formerly poor oats and rye were raised. (7) Bare fallowing is rendered unnecessaiy. (8) The climate is improved both for men and live-stock. (9) The soil is enriched by what the rain brings down. (10) All the processes whereby plant-food is made available in the soil are promoted. 342. Drainage systems may be put into three classes : (1) Deep, thorough, parallel, furrow, leading, closed, covered, or minor drainage, which is an underground system for carrying water off the field. (2) Arterial — that is, the improvement of natural water- courses, or the making of large new ones. (3) Sink hole, dumb well, or swallow hole, which is the sinking of a shaft through impervious clay to a gravelly bed underneath. 343. The first-named class is what is generally under- stood as drainage. The early methods were generally carried out in clay lands, and consisted of ditches or ' thorows ' (hence ' thorough ' drainage) cut about two feet deep, and filled with some material, which on decay- ing left a channel for water to flow. In the Essex system, hedge cuttings, brushwood, twisted hop-bines, straw, or DRAINAGE SYSTEMS AND METHODS. 207 stubble, was placed at the bottom of the ditch, and the earth firmly replaced. The systems which next came into use were those of Smith of Deanston and Josiah Parkes, and the points may be best shown by comparison. Smith of Deanston's Views. Josiah Parkes's System. I. Frequent drains at intervals, Less frequent drains, tlie in- 10 to 24 feet. tervals being from 21 to 50 feet, with a preference for wide intervals. IT. Shallow depth not over 30 Deep drains with a minim urn inches, object being to free depth of 4 feet ; the object that depth of soil from stag- being to take away all stag- nant water. nant water, and convert fall- ing water into a fertilising agent, III. Parallel drains at regular Parallel drains same as Smith, distances throughout the but increased depth corn- whole field, without refer- pensating for increased width, ence to wet and dry portions. IV. Stones preferred to tiles Pipes of 1-inch bore the best, and pipes. 344. The next system w^as one of alternate deep and shallow drains, and called Herrini^ Bone. The modern system is a compromise, drains being of medium depth and width, and varying with the soil. 345. The first step in drainage is to find the cause or causes of wetness. Where irrigation is practised, drainage itself is the first step, and an indispensable one. Tlie signs that show the want of drainage are : (1) Plarits have a loltliered and sicMy ap'peavance^ and a bleached or yelloioish colour ; (2) freshly turned farrow- slices shoiv a glazed sur- face ; and (3) the ajppearance of sedges, rashes, and other coarse grasses. 208 PRINCIPLES OF AGRICULTURE. The causes of excessive wetness may be (1) too much rainfall for the natural means of escape by the subsoil ; (2) the presence of springs, or (3) of soakage water which has come from a porous stratum. 346. From whatever cause a soil requires drainage, the first operation is to sink trial pits or water-level test holes (fig. 92). The height at which the water stands in the test holes will indicate the ^°' ''' height of the water-table in the soil, and from this information we can determine the depth of the drains which will best meet our requirements. The second operation is to find an outlet and outfall. When the soil allows for percolation of water, the outfall must be more capacious than when the soil is impervious. 347. We have already noted that evaporation is lessened by drainage, and this is shown by an experiment conducted by Mr Charnock : Mean of 5 Years. The rainfall was 24-60 inches. Tlie evaporation from soil saturated 32-68 „ Evaporation from drained soil 19-74 n This shows that from un- drained soil the evaporation exceeded the rainfall by 8 inches, whilst from the same soil with the same rainfall the evaporation through drainage was reduced to 5 inches less than the rainfall. The excess of evaporation over rainfall in this instance was due to soak- age water. Besides stopping excessive evaporation, drain- DRAINAGE SYSTEMS AND METHODS. 209 age lowers the water-table as in fig. 93, giving plants a large area to grow in, and consequently mitigates the effect of drought. It also has the very practical result of increasing produce, as shown in the following table con- structed by Mr Thomson, Hangingside : Kind of Crop. From Inferior Land, From Good Land. Before being drained. After being drained. Before being drained. After beiiig drained. In the first rotation. In the second rotation. In the 1 In the lirst [ second rotation. | rotation. Barley Oats Bush. pks. 23 3 35 2| Bush. pks. 33 1 47 2i Bush. pks. 29 U 44 H Bush. pks. 27 3 38 Bush. pks. ■ Bush. pks. 38 36 2 52 li ; 50 348. The depth of a drain will vary (1) according to the character of soil and subsoil as shown in test hole ; (2) the depth of feeding-ground desired, and (3) security from tillage operations. The distances apart must also be studied at test holes, as intervals and depth beyond require- ments is simply waste. Experience has shown that a drain in a porous soil will draw from five to six times its depth on each side, in medium soils four to five times, and in clays two to three times its depth. 349. The cutting of drain trench is shown and may be divided into three sections. The illustration is for a 3^-foot drain, in which case the top spit, 14 or 15 inches wide, and 8 or 9 inches deep, can be removed by a digging spade or plough. The next section, the shaft of the trench, is dug out by a long-bladed draining spade. In depth this section will be 24 inches, and at the bottom 10 inches in width. The third section, the bottom of the trench, will be about 9 inches deep, dug out by draining spade and scoop, and just wide enough to admit the pipe. The direction of Fig. 94. 210 PRINCIPLES OF AGRICULTURE. the drains is at right angles to the main drain, but the contents are delivered at an acute angle. This is done by curving for a few feet the ends of the drains before they are joined to the main in the direction in which the water in tlie main is flowing. 350. The cylindrical drain-pipe is now in common use in the United Kingdom, and the egg-shaped pipe a favourite in America, and coming into general use ; but we will look at some of the difi'erent forms of drains which were in use at various periods, as many of these, though considered obsolete by the scientific drainer, can be advantageously used in the colonies, where drainage must be for some time in a state of Fig. 95. evolution. Fig. 95 represents a drain which is filled at the bottom with fagots, brushwood, poles, or tliorns, and the soil returned to its original place of top. These drains are a rough-and-ready way of draining land where wood is easier to obtain than even stones. 351. The next class of drains are known as wedge and shoulder drains, and are made of the surface turf. Fig. 96a shows that the surface turf has been lifted and cut to the size desired, and then placed grass downwards as a wedge in the shaft of the trench. The next (fig. 96^>) shows this wedge-shaped turf supported by a shoulder, and in fig. 96c the entire turf is employed. After placing the turf in any of the positions shown, the soil is firmly returned above it. 352. Plug-draining can be carried out in clays. A string of wooden blocks — poles or fagots — ^joined together by iron bands is laid at the bottom of the trench, and when clay has been puddled over this, it is drawn forward by means of a chain and lever and the operation repeated. Fig. 96. DRAINAGE SYSTEMS AND METHODS. 211 353. Stone drains are either made with small stones about 3 inches in diameter, or with flags or flat stones. In stone drains the turf is replaced when the trench is filled up. Fig. 97a shows a common stone drain as advocated by Smith of Deanston. Fig. 97 b shows a drain made by placing a flagstone on edge in the bottom of the trench and .t^ '*^W{Ma'< Fig. 98. Fig. 97. covering it with small stones, and another form is shown in fig. 97c. Figs. 97d and 97e show the use of flat stones in making triangular and square con- duits, and when these are well laid on a firm bottom, they have proved as drains to be practically indestruct- ible. 354. Peat drains are made with what may be termed peat pipes (fig. 98a). The peat is cut by a special spade, and when two peats are placed as shown in drain, a conduit for water is formed. Fig. 98b is a drain made with bricks which have a groove scooped out on one side, and when placed as shown, a channel for water is made. 355. The earliest form of tile drainage is shown in fig. 99a. The tile was like a horseshoe, and had broad flanges on which it rested on the bottom of the drain, and the toj) of the tile was pierced with holes to admit water. Fig. 99/; shows a drain with the actual horseshoe tile. They >yere laid on flat soles of tile or wood, then made with the 212 PRINCIPLES OF AGRICULTURE. Fig. 99. sole attached. Combinations of these tiles were made when a larger water capacity was desired. One was placed under the other, divided only by the sole, or three of them were placed like a pyramid. 356. The cylindrical form of pipe is shown in fig. 100«, and in practice it is found to possess advantages over every other kind. They assume three forms (fig. lOOZ^), and of these the egg-shaped is theoretically correct, as the very slightest flow of water will keep it free from sand and sediment. 357. Collared pipes, when there is a risk of displace- ment, are also occasionally used (fig. 101). Ordinary pipes may be put into a loose collar as shown (a), or the pipes may have a collar attached (h), and this form may be Fig. 100. Fig. 101. made water-tight, and is very serviceable when near trees or hedges. 358. We have noted some of the leading features in drainage, but a good deal more has to be learned which is just as necessary to understand the system thoroughly, but cannot very well be taught within the compass of this chapter. But we may finish by noting the causes of stop- page of drains. It may be due to (1) displacement of the pipes; (2) tlie accumulation, of sediment in the pipe; (3) the roots of trees or the crop in search of water entering into the pipe and filling it up like a sponge ; (4) the DRAINAGE SYSTEMS AND METHODS. 213 deposition of iron in the water as a sediment in the pipe ; or (5) the growth of fungi — green sludge. Questions.—!. What are the causes of stoppage in drain- pipes? 2. Should drains he shallow or deep in (1) clay, (2) light or shallow soil, and (3) deep alluvial soil? Give reasons why. 3. Explain the principle of sink-hole drainage. 4. What are the economical advantages of draining soils ? 5. What are the causes of excessive wetness in land, and the signs that show the want of drainage ? 6. On what points does the depth of a drain de- pend ? 7. What are shoulder drains and plug drains ? 8. Sketch the outline of some tile drains, and state the kind of tile used. 9. What is the connnon form of tile now used ? What form is theoretically the hest ? CHAPTEE XLIV. IRRIGATION. 359. Another way of improving land is by irrigating — that is, running a quantity of water or liquid manure over the land. It is a practice more common in India, Australia, California, and the continental states than in the United Kingdom, and gives the best results in warm climates. 360. One of the advantages of irrigation is, that it supplies sufficient moisture to the soil and plant. We know that there is an absolute necessity for water during plant growth ; in fact, from 5 to 9 per cent, of water must be present in the soil before the soil can supply water to the plant. Growing plants contain from 70 to 95 per cent, of water, and to that extent it is an actual want. In our ordinary farm-crops, from germination to maturity, water is transpired by the leaves, and the amount so used equals a depth of 12 inches over the whole soil covered by the crop. If a crop be stimulated by manures, a greater supply of water will be wanted. 214 PRINCIPLES OP AGRICULTURE. 361. By irrigation valuable plant- food is carried to all parts of the roots. Plant-food is matter soluble in water, and if the water-supply be inadequate, an insufficient quantity of nutriment is carried into the plant, and its growth is stunted or arrested ; and we know water can only enter by the roots. 362. Irrigation can also be practised at all seasons. Summer irrigation supplies moisture ; winter irrigation, fertility. In certain districts in Australia, and in whole provinces in India and southern America, which are sub- ject to drought in the growing season, water becomes the measure of fertility, and it is well established that the amount of growth depends upon the quantity of water supplied to a crop. Winter rains do crops little good — it is not their growing period — while summer rains would do good, but they are more of a sudden downpour, and seldom can be retained by the soil. "We see this in the heavy floods in the colonies, as the land gets cleared and the means of transpiration by trees is checked. When a large proportion of the country was covered with forest vegeta- tion, the newly-cleared land was filled with decaying organic matter, absorbent of water, as it was not then subjected to the influence of sweeping winds. I^ow, when the country is cleared, denuded of forests, and organic matter is being used up by continuous crop-growing, the rainfall is not held, and passes olf immediately, showing, itself in floods where formerly such a thing was unknown. 363. Irrigation is a cheap and ready means of making use of liquid manure- and town sewage. Water itself con- tains saline and fertilising matters — dissolved and invisible, — and by giving moisture enables manures to act. For example, Indian corn when abundantly watered has been grown on the Andes in almost moving sand ; and it is a matter of observation that light soils produce better in rainy years than in dry ones. It has been found that crops ItlRIGATION. 215 suffer less from drought on land that is well manured, in comparison with land inadequately fertilised ; and that a small amount of manure will do more good on irrigated land than a large quantity of manure on land without moisture. 364. By irrigation, when the drainage is good, acid and poisonous substances naturally present in the soil are washed away, and the temperature of the soil is improved when the water is warmer than the air. 365. The supply of water and the power to bring it into position are two requisites in irrigation ; and there are two circumstances under which it will not pay to irrigate, and these are : (1) When the lands are above the source of water-supply, and the cost of raising and making reservoirs for holding water would be more than the value of the benefit received. (2) When the land is so low that you cannot irrigate without a perfect system of sub-drainage, and the cost of this exceeds value of benefits. Wells are considered only to pay in market-gardens, where the high value of crop covers cost of raising water. The familiar unit of measure is the rate of one cubic foot per second, and it is calculated that only from one-half to one-third of the water applied is absorbed. 366. Three things must rule the amount of water to be applied : (1) Nature of soil. (2) Character of the climate. (3) Nature of the subsoil. (1) We must consider the nature of the soil, because soils differ in their power of absorbing and retaining water. Coarse gravel Avill not retain water; pure quartz will absorb little and part with it readily. Alluvial soils will absorb a quantity and retain it for a loug time. In France, they say that soils with 20 per cent, of sand are 216 iPRINCIPLES OF AGRICULTURE. to be irrigated once in fifteen days, and soils with 80 pef cent, of sand once every five days. (2) The character of the climate has to be considered, as quantity of water applied must differ in places which have an average rainfall of 40,. 20, or 10 inches. The direction winds are blowing have to be studied ; sometimes they are charged with moisture, at other periods they are thirsting for it. Climatic effects can be well illustrated by different legal allowances. In Italy, one cubic foot per second is considered sufficient for four acres ; in some parts of Spain, one cubic foot per second is the legal allowance for 70 acres, in other parts it is the allowance for 240 acres, and in some parts even for 1000 acres. (3) The character of the subsoil is a serious element in calculating the amount of water to be supplied. If the soil rests on coarse gravel, it will be like a sieve ; if on clay, just the reverse. The nature of the subsoil will determine the amount of loss by absorption ; the minimum figure estimated is 15 per cent. 367. The cost of irrigating is most where the area is small, as in gardens and market-gardens. It is least in meadows and pasture, when the channels are permanent ; and between these two come arable lands, where after each ploughing fresh channels have to be made. The systems commonly employed are the catch, meadow, or hillside; ridge and furrow or bed-work ; sub-irrigation, pipe irriga- tion, side irrigation, and sewage and liquid manure irrigation. 368. The catch-work system is seen in illustration (fig. 102). The feeders, ah, are at the highest point of the ground, from whicli the water overflows and runs to a lower level. In the overflow from ah the water finds its way to cd, which collects what comes to it as a drain; but in turn it acts as a feeder, and the surplus water descends to ef, which sends, it to gli, which again sends it on op, and IRRIGATION. 217 Part of the water which sends it to the main drain, Im. finds its way to the drain 71, which flows into the main drain, and the drain k can be used as a supply cliannel without waiting for overflows from higher levels. It must be re- membered that no descrip- tion of the catch- work system can have a univer- sal application. AB is a cross- section from ah to Im. regular in fig. supply Furrows for a slope are shown 103 : a is the channel, and h the surplus water drains, and the land be- tween ah is covered with a thin sheet of water or a net- work of small streams. ^^'^'Ob "=^r- c ci e TV f k "y h. I p m ^ Fig. 102. 3G9. The bed-work system is also shown by figs. 101 and 105, the latter showing the principle : a is the ridge and Fig. 104. h the furrow, while cd and ef are supply channels. The water is run on at the ridges, and surplus taken away by the furrows. The forms of furrows for running on and taking ofl' water are various. The typical one is as shown 218 PRINCIPLES OF AGRICULTURE. !l ^*^~*' c 3S>-> I I If 1 1 \ i 1 f I I I i i i <- _ i e ^ / i a. 1 i 6 i ill fig. 106, wliere the furrow-slice forms a bank, and prevents the water from a neighbouring channel getting in. 370. Sub-irrigation is saturating the soil with water by drains below the surface, and is the reverse operation to drainage. From main open drains the water is forced by pressure up these drains, and rises in the soil by capillary attraction. By this system the surface soil is not touched or harmed. This system has been employed in California, and it is said that a quarter of the water used underground is better than the whole on the surface. 371. Side irrigation is the soakagc of water from the sides of open drains. The next system, pipe irrigation, may be either above or under the ground. Iron pipes arc laid on the surface of the field, about thirty feet apart, and water pumped by steam-power through them. As the pipes are perforated, the land is showered as from the rose of a watering-pan. Another system is to have an elevated reservoir, and from this, at right angles, iron pipes are laid in the ground below the plough-line. To these pipes hydrants are attached, and the ground irrigated by a hundred feet hose. Fig. 105. Fig. 106. IRRIGATION. 21^ 372. Some points i-egardiiig irrigation must not be lost sight of. Irrigation is intense culture, and it is a highly advanced condition of agriculture ; and for successful irriga- tion the primary condition is drainage, natural or artificial. All waters will do for irrigation except those containing iron or draining from forest or bog land, or those containing the refuse of dye-works, chemical works, and other manufac- tures. The water should be kept flowing, but not allowed to run too long over one place. The application of water lower in temperature than the soil is injurious, and when water is applied on a clear, sunny, or windy day, the effect is to increase evaj^oration and cool the soil. Water should be applied moderately a day or so before sowing or transplanting, and to growing plants frequent moderate waterings should be given. There is far greater danger at this stage of giving too much rather than too little. Further, a soil should not be disturbed when wet ; hoeing, cultivating, weeding, &c. should be done when the soil is dry. 373. Sewage irrigation may be considered to be simply filtration. Light soils resting on a sandy subsoil will be found to be the best absorbents of it. A portion of the sewage of the Old Towm of Edinburgh is used as an irrigant on the meadows of Craigentinny, and sewage farms are to be found both in the colonies and at home. Sewage is usually distributed by gravitation. 374. A form of irrigating with liquid manure is shown in fig. 107. A head of water or liquid manure is obtained in a tank, from which it flows by main pipes under the ground to reservoirs ; then it can be turned on the land by pipes. This system is employed in market-gardening. A is the tank into which the sewage or liquid manure has been pumped up, and B the main pipe, deep underneath the ground, which carries the liquid manure to the distribut- ing centres, C. From these centres, on the surface of the 220 PRINCIPLES OP AGRICULTURE. soil, pipes, D — 12 feet long, with spigot and faucet joints, a^e laid as desired. When pipe Bd is removed, the liquid will issue from Dc and irrigate the section 3-4 ; and when Fig. 107. Dc is removed, it will issue from Dh and irrigate section 2-3, and so on. Questions.— 1. Name some of the advantages of irrigation. Will it always pay to irrigate ? 2. What three things rule the amoimt of water to he applied to land ? Explain the reasons why. .3. Name some of the systems of irrigation, and explain fully one of them. 221 NATURAL AND ARTIFICIAL FERTILISERS. [6. Manures. — Object of manuring the increase or maintenance of the fertility of land — Removal of i^lant-food from land hy drainage, crops, and ayiimal 2^'i^oduce ; return of plant food in manure. Application of chalk, marl, or lime, an ancient practice — In chalk and marl lime is combined with carbonic acid, as in soil — Continual ivaste of lime from surface soil — Recapitulate physical and chemical effects of carbonate of calcium in soil — It also aids decomposition of silicates, neutralises humic acid, promotes oxid- cdion of vegetable nmtter — Lime, how prepared from limestone ; its behaviour ivith ivater {hence ' quick ' or endowed with life) ; the chemistry of these processes-^Chemical effects of lime at first far 7nore energetic than those of chalk — The conversion of lime into carbonate in the soil — Lime from dolomite [if this is a local rock), the difference in its composition and action — Give detailed com- X>osition of marls if these are used locally — Soils and crops speci- ally benefited by liming — Quantities of chalk and lime applied. Precautions necessary when quicklime is employed. Farmyard 7na7iure composed of liquid and solid excrements plus litter — Solid excrements are undigested matter ; liquid, contain the nitrogenous ivaste products of the body, principally urea — Distribution of ash constituents betiveen them — Comp>arative value of liquid and solid p)ortion — Richness of manure dependent on character and amount of food, and on the use made of food by the animal — The manure of different aniirmls, characteristic differ- ences as to p)roportion of water — Different kinds of litter, their comjiosition and absorptive 2)0wer — Quantity of litter required for a horse, cow, and fattening ox, and quantity of fresh manure yielded — Fermentation of urea — I^osses of ammonia in stable frotn various ani^nals; how best diminished — Box feeding, its advan- tages — Feeding in open or covered yards, its advantages and disadvantages — Losses by drainage — Liquid manure, its com- position; hoiv dealt luith — Formation of tnanure heap — Fermen- tation of dung, its results — Losses in the manure heap, how pre- vented — Advantages of apjilying fresh manure to the land — Com- position per cent, and p)cr ton of farmyard manure — Its character 99 9 PRINCIPLES OF AGRIGUlvTURE, as a general manure — Its injlnence upon the physical properties of soils — Quantity available for use on a farm; how best employed — Slow action of the plant food it contains — Advantages of feeding animals upon the land. Bones, fresh, steamed, and boiled, their composition — For^iis in which employed — Soils and crops most benefited by their use — Quantities ajjj^lied — Sloicness of action. Superphosphate, the object of its manufacture — Chief nmtericds used — Chemistry of the process — Meaning of the terms tricalcic, dicalcic, and monocalcic phosphate, also of the commercicd, ^soluble,' ^reverted,' and ' insoluble ' phosphate — Composition of superphos- phate — Its action as manure compared with bone — Soils and crops most suitable for its use — Quantities applied — The combinations formed by phosphoric acid in the soil. Nitrate of soda, luhence obtained — Its composition — Nitrcdcs a naturcd plant food — Soluble, not retained by the soil — Precau- tions necessary to employ nitrate of soda advantageously — Crops most benefited by its use — Quantities employed. Kainitc, its composition, its origin — Freely soluble, but potash and nmgncsia retained by a good soil — Soils _ and crops most bene- fited by it — Quantities apjjlicd.^ CHAPTER XLV. MANURE. 375. Having now studied the various substances which crops require from the soil, with their chemical composition, and the way in which their quantity decreases in the soil, we will now be able to understand a description of the various manures that are employed by farmers to supply the defi- ciency of any or all of these substances ; the object of manuring being the increase or maintenance of the fertility of the land — that is, the available plant-food it contains, seeing that this plant-food is removed from the land b}'- drainage, crops, and animal produce. 376. It has been found that, as a rule, nitrogen, phos- phoric acid, and potash are the substances that require fJdf'Jlfj to be applied to soils to make or keep them fertile^ MANURE. 223 the others being generally present in sufficient quantities for the immediate and future requirements of crops. There is, however, one notable exception to this rule in the case of peaty soils. As we know, they contain scarcely any mineral matter at all, and therefore require manuring with all the ash ingredients. So, after being well drained, these soils are thoroughly dressed with clay before being culti- vated in order that they may have the needful supply of mineral matter for crops. Lime is often largely applied to soils, but not so much as a plant-food as to sweeten them, or to set potash free in a soluble condition for the use of crops, by taking its place in the insoluble portion of the soil. 377. Of the three most important manurial substances just mentioned, nitrogen is the most expensive to buy, but phosphoric acid is the one which requires to be most largely purchased by the farmer. The greater part of the phosphoric acid taken up by a plant is at last carried into the seed, so that a farmer, by selling his wheat and barley, removes the phosphoric acid which these grains contain completely from the farm. The percentage of phosphoric acid in cultivated plants is given by Messrs Way & Ogden, and others, as follows : Phosphoric Acid Proportion of Ash. in Ash. AVheat, average 1-67 46-00 Do. straw 5-10 5-43 Bailey, average 2-34 35*20 Do. straw 5-36 • 326 Oats, average, inchiding husk 2-90 18'19 Do. straw 5-10 3-19 Beans, grain 4-00 37'57 Byegrass, (hied 5*89 13-51 Meadow hay, dried 8'06 9-85 Bed clover, dried 11-17 4-12 Turnips, bulbs -78 9-74 Potatoes 1-03 13-55 Mangels -88 4-19 Carrots -91 8*55 224 PRINCIPLES OP AGRICULTURE. But the greatei* part of the potash, and ahnost all the silica and other ash constituents, are contained in the straw, and as this is mostly returned to the land again in the farmyard manure, the soil is not permanently robbed of them. 378. Again, the young animals that are reared on a farm require phosphoric acid to form their growing bones, for bones consist chiefly of phosphate of lime ; and fat animals that are sold off a farm for human food carry away in their bones a great deal of phosphoric acid ; also milk, which is largely sold for human food, carries with it phosphoric acid, which would, naturally, help to form the bones of the young calf. Phosphate of lime is the most abundant ingredient in the skeleton of all the higher animals, which is made up of about 33 parts of water, 40 phosphate of lime, 7 carbonate of lime, and 20 of gelatine. Now in each of these cases the phosphoric acid has been obtained from the food which has been grown on the farm ; so we see, a farm suffers a great loss of this scarce sub- stance by rearing young stock, and selling fat stock or milk. The potash, on the other hand, is little needed by animals, and passes from them chiefly in their urine, and may there- fore be returned to the land in the farmyard manure. 379. Much the same may be said of nitrogen as of phosphoric acid ; it is largely contained in the seeds, and milk or flesh of animals that are sold off' a farm, and is required to make the lean or muscle of young growing stock ; but a small quantity is regularly carried into the soil from the atmosphere in the form of ammonia or nitric acid dissolved in rain-water, and crops of the clover tribe also have the power of absorbing through their root nodules some nitrogen from the atmosphere ; so that by good management, much of the nitrogen which is sold off" a farm will be again replaced without purchase. 380, Farmers have found that by buying nutritious foods for their cattle, such as oilcake, they greatly increase the MANURE. 225 quantity of nitrogen contained in the dung ; and so, with the natural supply just mentioned, they can replace the nitrogen sold off the farm. But if they wish to keep their land productive, they must buy phosphoric acid. Although phosphoric acid is not the most abundant ingredient in the ash of plants, yet from its comparative scarcity in the soils of nearly all districts of the world, and the very marked effect which the absence or abund- ance of it in the soil produces on the development and quality of all our useful cultivated plants, it is by far the most important ingredient amongst those which require to be added to the soil to increase the quantity and quality of cultivated crops. Phosphorus, combined with oxygen and calcium as phosphate of lime or calcium phosphate, can be detected in minute quantities in many rocks, as well as in all fertile soils ; yet in most of these the quantity is so small, or is combined in such a manner, that phosj^hate of lime in some form must be applied to ail lands that are not excessively rich, or have been long in cultivation before full paying crops of good quality can be produced. In many parts of the United States and Canada sulphur seems to be more deficient in soils tlian phosphorus, and a top-dressing of plaster — -i.e. sulphate of lime, produces a more marked effect upon crops than even phosphate of lime. In districts having a very dry climate, such as Hungary and the south of Eussia, where the soil is also rich, top-dressing with artificial manure has little effect, but in the poorer soils of countries having a moderate summer rainfall, a top- dressing of phosphate of lime has usually a beneficial result. The proportion of phosphoric acid in soils varies up to 40 parts in 10,000, or about 4 tons per acre in 10 inches of soil; the black earth of liussia contains about 15 parts in 10,000; but the fertility of a soil, so far as it depends upon the phosphoric acid, is regulated not so much by its quantity as by the combination in which it exists, render- o 226 PRINCIPLES OF AGRICULTURE. ing it available or non-available to the plant. In Australia, all through the country, with but few exceptions, there is a marked deficiency of phosphates in the soil. We shall explain in a later chapter the various sources of supply of this substance ; but we can now pretty plainly see the reason why of the three important plant-foods — nitrogen, phosphoric acid, and potash — the phosphoric acid is the one which will pay the wise farmer best to use judiciously. Questions, — 1. What is the object of manuring? How is plant-food removed from the land? 2. Name three most im- portant maniirial substances. 3. Why is phosphoric acid of such importance as a manurial agent ? CHAPTEE XL VI. THE CHARACTER AND PREPARATION OF FARMYARD MANURE. 381. Farmyard manure is a 'general' manure — that is, it supplies all the essential elements of plant-food, and consists of the dung and urine of farm stock, and the straw which has been used as litter. Of these, the dung contains nearly all the phosphoric acid, and the urine and straw nearly all the potash; the urine also contains the most nitrogen, but the straw scarcely any. One thousand parts of animal excrements contain : Cow. Horse. Sheep. Pig. Water Solid matters* Dung Urine 860 915 140 85 Dung Urine 750 900 250 100 Dung Urine 640 950 360 50 Dung Urine 760 976 240 24 * Containing Nitrogen 1000 1000 .3-6 9 .3-0 ... 2-2 16 1000 1000 60 11 4-0 ... 3-5 14 1000 1000 6 8 5 3 8 1000 1000 7 '0 3 -0 Phosphoric Acid... Potash and Soda... 5-0 1-2 6-5 2-0 PREPARATION OF FARMYARD MANURE. 227 From this, it will be seen that farmyard manure without the urine would he poor in nitrogen, and would also lose a considerahle amount of potash ; without the dung, tliere would scarcely he any phosphoric acid ; and by omitting the straw, there would be a loss of potash and other ash ingredients; besides which, the straw is necessary to absorb the liquid urine, and so prevent waste, as well as to render the whole of convenient consistency for easy removal. 382. A hundred pounds of well-rotted farmyard manure generally contains seventy-five pounds of water, a little more than half a pound of nitrogen, about half a pound of I)otash, and less than half a pound of phosphoric acid. Hence there is but one pound and a half of these three substances in the twenty-five pounds of dry matter; so that it is a most bulky manure, and therefore has to be carted in large quantities to the land, and requires some labour to spread it properly. From this, it will be seen that it is expensive in its application to the soil, and yet its bulk is of value ; for it opens up stiff soils, and adds much humus to light soils, which helps them to absorb and retain moisture and ammonia for the use of plants. Farmyard and stable manure is not only bulky, but, all things considered, costly to prepare and costly to apply. The great bulk of it consists of water and vege- table matter, and it is used to the beat advantage oidy in the immediate neighbourhood of its production, where little transport will be required. When rotten, it contains nitrogen, and all the ash constituents in a soluble condition, ready for the present use of the crop ; but it also contains still more in an insoluble form, which becomes soluble by degrees, so that it supplies a crop steadily with food through the whole period of its growth. This is a great point in its favour. 228 PRINCIPLES OF AGRICULTURE. COMPOSITION OF WELL-ROTTED FARMYARD MANURE. Soluble (utilis- Insoluble (utilis- niofal able at once, able in the future). ^ • Water ... 75'4 Organic matter 37 12-8 16-5 [yielding Nitrogen] [-3] [-3] [-6] Potash -45 -04 -49 Soda -02 -04 -06 Lime -33 1'67 2- Magnesia -05 -09 -14 Iron Peroxide '5 "5 Sodium Chloride -04 ... '04 Phosphoric Acid -18 -27 -45 Sulphuric Acid -06 '06 '12 Carhonic Acid -1 1-3 1*4 Silica -26 2-4 2-66 Loss ... '24 100-00 383. Farmyard manure is termed, as already noted, a general manure, because it supplies all the kinds of food required from the soil by plants. Those which only supply one or two manurial substances to a crop are named special manures. Manures are sometimes divided into two classes, termed 'natural' and 'artificial;' and further subdivided into ' animal ' manures, ' vegetable ' manures, ' guano,' ' phosphatic ' manures, and ' saline ' and ' earthy ' manures. All materials which are used for the purpose of supplying plant-food to the soil are called fertilisers. Tlie following is a list of the fertilisers now generally used. There may be many fertilisers bearing different names, but their names are only given them by manufacturers as a trade mark. They are all made from materials in the follow- ing list ; and as regards application, considerable skill has to be exercised. Fertilisers, natural and artificial, are used to feed the crop, and what is not subsequently recovered by being utilised by a crop during growth is simply wasted. PRfiPARATloisr 0*" FARMYARD MANURE. 220 LIST OF FERTILISERS. Mainly Nitrogenous. Nitrogen only Nitrogen preponderating, but containinfj also smaller quantities of phosphoric acid and potash Nitrogen and Potash Mainly Phosphoric Acid. Phosphoric Acid only Phosphoric Acid preponder- ating, but containing also smaller quantities of nitrogen Potash Manures. Potash Salts only. A well-balanced Fertiliser. ) Sulphate of ammonia. ( Nitrate of soda. Farmyard and stable manure, night-soil, dried blood, desic- cated slaughteryard refuse, and fish manure, horn, damaged cakes, shoddy, &c. Nitrate of potash (saltpetre). («) Phosphoric acid slowly soluble: Bone ash, bone-char, mineral phosphates, Thomas slag, some guanos. (b) Phosphoric acid readily sol- uble : Superphosphates made from bone-ash, bone-char, and mineral phosphates, and ^ some guanos. f {a) Phosphoric acid slowly I soluble : Bone-dust, bone- ! meal, and some guanos. (b) Phosphoric acid readily sol- uble : Superphosphates made from bone-dust and from some guanos. ' Crude and impure, such as kainite. Pure and concentrated, such as muriate and sulphate of potash. Compost heap made from de- cayed vegetable matter, such as decayed -wood, kitchen refuse, road sweepings, weeds, fallen leaves, and forest gleanings. 230 Principles of agriculture). 384. All farmyard manure is not of equal value, and for many reasons. The richest manure is obtained from the horse stable. Here no flesh or fat is laid on or milk sold, and the only loss is the work done, and to repair this the carbon compounds in food are used ; further, horse urine is more concentrated. Sheep dung is more like horse manure. Stock that are being fattened on corn, oilcake, or other nutritious food, produce dung and urine richer in nitrogen than others. Young animals that require the phosphoric acid and nitrogen to help to build up their bone and muscle, take more of those substances from their food, and therefore produce a poor manure. Milking animals, too, produce a poor manure, because of the demand upon their food for the nitrogen and mineral matters required for the milk, so that the age and food of an animal, as well as the purpose for which it is kept, greatly influence the quality of the manure produced by it. We have seen that farmyard manure is composed of the liquid and solid ex- crements of animals plus litter. The solid excrement is made up of undigested matter; the liquid contains the nitrogenous waste products of the body, principally urea, and this is considered to be an available source of nitrogen to plants. The composition of farmyard manure depends on the animals contributing it, the character and amount of their food, and the use made of the food hy the animal, along iDith the nature and amount of litter added. Reference to the analyses already given will show that there are character- istic diff'erences as to proportion of water in the manure of different animals, and that the distribution of ash con- stituents in the liquid and solid excrements also varies. Cattle dung, tliough most abundant, is the least valuable in composition. It decomposes slowly and gives out little heat, hence it is called a cold manure. The urine of cattle is richer as a fertiliser than their excreta. Horse dung contains less water than cattle dung, and decomposes rapidly PRiiPARATION OF FARMYARD MANURE. 23 1 in tlie soil, and is therefore a liot manure. Sheep dung decomposes more rapidly than cattle dung, and not so quickly as horse dung. It is richer in solid matters than the former. Pigs' dung decomposes slowly, and it may be either rich or poor according to the feeding of the animal. Birds' dung partakes more of the nature of urine than fseces, and is a good manure when obtainable. The com- position of this dung is given by Professor Anderson as : Hen. Duck. Goose. Pigeon. Water 60-88 46-65 77-08 58-32 Organic matter* 19-22 36-12 13-44 28-25 Phosphates 4-47 3'15 0-89 2-69 Sulphate of lime ... ... 1-75 Carbonate of Ume 7*85 3-01 Alkaline salts 1-09 0-32 294 1-99 Sand 6-69 10-75 565 7-00 100-00 100-00 100-00 100-00 ♦Yielding Ammonia... 0-74 0-85 0-67 1-75 The straw of oat, wheat, and barley, which is the litter generally of cattle, contains about five parts of nitrogen, ten of potash, and three of phosphoric acid per 1000 parts; and as 2000 to 3000 lb. of straw is obtained per acre, when returned in farmyard manure the soil gets back some of the ingredients extracted. Bracken fern, peat moss, sawdust, and other substances are also used as litter. The greater the absorbent power of the litter, the better will be the manure, and roughly-chaffed straw and peat moss litter gives a good consolidated bed of dung. 385. Then, again, farmyard manure may be almost entirely spoiled by bad management; hence it is very important that a farmer should manage his manure in such a way as to prevent loss of valuable plant-food. And this is the more important from its being an expensive manure 232 IPRINOIPLES of AGtllCULTUilE. both to make and apply to the land, and yet so valuable as a food to all kinds of crops when really well prepared. It is not at all uncommon for the urine, which is of nearly double the value of dung, to be allowed to run to waste. 386. Farmyard manure in the United Kingdom is princi- pally made in the stock or fold yards in winter, when it is too cold for farm animals to be left in the open fields. Sometimes these yards are covered, but move frequently arc open to the sky, with sheds on one or more sides for the shelter of the live-stock. When they are open, they receive the whole of the winter's rain, and therefore require much more straw to absorb the moisture and make them comfort- able for the cattle. Sometimes you see a yard in a miser- ably wet state — the cattle half-way up to their knees in slush ; in other cases they are so well cared for, that they are almost knee-deep in clean straw. ISTow, in neither case are you likely to get a really good manure; for in the former a great deal of the valuable manure would probably run away in the gutters and be lost ; and in the latter, tlic manure would consist of little else than straw. In order to obtain good manure from an open yard, and at the same time keep the cattle comfortable, the sheds should be troughed and spouted to catch the roof-water, which Avould otherwise stream into the yard ; only just sufficient straw should be used as litter ; and a tank should be provided to collect all the liquid draining from the yard and stable's, that ■ nothing be lost. In a covered yard, less straw is required to keep the cattle comfortable and absorb the moisture, because no rain falls there, and so the best manure is obtained from it. Yard manure gets w^ell mixed and pressed down by the cattle walking about on it ; and when it reaches a depth of a foot or more, it is, on some dry frosty day, carted out and' laid in a large heap. Manure produced by cattle in boxes — box feeding — is much superior PREPARATION OF FARMYARD MANURE. 233 to ordinary farmyard manure, and this is due to less straw being used and the urine being almost entirely preserved. Way's analysis shows : Bnx Ordinary M-- "Sir* Water 71-40 7100 Dry matter * 28-60 29-00 100-00 100 00 * Containing Nitrogen = to Ammonia 2-37 1-70 Phosphoric Acid 0-30 0-26 Potash and Soda 2-00 O'SO 387. In the dung-heap two sources of loss have to be guarded against — drainage, and excess in fermentation. The way in which this heap is made is a matter of great import- ance ; and we must study the chemical changes which go on in the manure-heap during its fermentation or rotting, in order that we may understand the reasons for the methods employed. Fermentation cannot proceed without the aid of air ; consequently, the more loosely the manure is heaped together, the more easily will air get into it, and the quicker will it ferment ; and the closer it is pressed together, the slower will it ferment. In fermentation, oxygen of the air combines with substances in the manure, and, as is always the case when oxidation takes place, heat is pro- duced. We can note how hot fresh stable manure gets, when placed in a heap for a cucumber bed. Now, if water be poured on the heap, many of the openings get filled with water instead of air, and the whole heap is cooled ; conse- quently, fermentation is checked. Both by pressing the manure tightly down, and also, if necessary, by a wise application of water, the heap may be made to ferment slowly. 388. But is there any advantage in causing manure to ferment slowly? There is a great advantage. We have 234 .PRINCIPLES OP AGRICULTURE. seen tliat in tlie decay of organic matter, amongst othef tilings, water, ammonia, and carbonic acid are produced; but besides these, other organic acids are formed from the con- tained hydrogen, carbon, and oxygen. We also know that ammonia with water acts as a powerful base ; consequently it readily combines with either carbonic acid or those other organic acids (humic acid, ulmic acid, &c.) to form salts. Now rapid fermentation favoars the production of carbonic acid, which combines with ammonia in the manner just described to form carbonate of ammonia (smelling-salts) ; but this is a M&vy volatile salt, and therefore flies away into the air ; and in this way the farmer may lose the nitrogen contained in the ammonia, which is so expensive and necessary for his crops. Even free nitrogen gas may pass off if the heap becomes too dry. On the other hand, the slow fermentation obtained under the influence of pressure and moisture, encourages the formation of the otlier organic acids which also combine with ammonia ; but the salts thus produced (humate of ammonia, ulmate of ammonia, &c.) are not volatile, and therefore do not escape into the air. They are, nevertheless, soliihle ; hence care must be taken that they do not run away, as they are often allowed to do, in the liquid which runs from a dung-heap. These are the substances which give the dark -brown (almost black) colour to the drainage-water of a manure-heap. In the rotting of the manure, much of the other insoluble matter also becomes soluble, and this, in like manner, may be carried ofl" in solution. Through fermentation the manure becomes ' ripe ' or mellow and better adapted to be of immediate, service to growing plants. Well-fermented dung is called * rotten ' or 'short' manure, and unfermented dung is known as 'fresh' or ' long ' manure. 389. Let us now return to the making of the heap. It should first of all have an impervious bottom, with some very absorptive substance, like dried peat, dry loam, PREPARATION OP FARMYARD MANURE. 235 or gypsum (sulphate of lime), laid on it to suck up the liquid manure. The heap should then be built higli in the middle and slanting down to the ground at each end ; each load sliould be drawn from one end right over to the other side before being emptied ; in this way the manure gets pressed very tightly down, load by load. The top should be made somewhat roof-shaped, to shed rain-water ofip, so that as little as possible may soak through. If the heap be made under a shed, loss from drainage will be saved, as in the case of the covered yard ; but there may be a loss in gas, from the heap becoming too hot and dry. This may be prevented, and the manure improved, by pump- ing the liquid manure from the tank over it, to cool and moisten it. Dung-heaps are sometimes covered with earth or sprinkled with gypsum to prevent the ammonia escaping, and an open drain is sometimes made round the heap, to conduct the liquid that would otherwise be lost into a well, from which it is pumped over the manure. 390. Dr Voelcker states that farmyard manure undergoes the following changes : (1) During fermentation the pro- portion of soluble organic and mineral matter increases. (2) During ripening, peculiar organic acids are formed from the litter and other non-nitrogenous organic matter. (3) These acids — such as humic and ulmic — form with potash, soda, and ammonia dark-coloured, very soluble compounds, as seen in the drainings from a dung-heap. (4) During fermentation, ammonia is produced from the nitrogenous constituents of dung, and it is partly held by the humus substances produced at the same time. (5) A quantity of volatile ammoniacal compounds escape into the air. (6) During fermentation the proportion of organic matter decreases, whilst the mineral substances increase in a corresponding degree. (7) But the proportion of soluble nitrates is larger in rotten than in fresh dung. 391. We have noted that cows and pigs produce a cold ^36 PRINCIPLES OF AGRICtJLtURlJ. manure, and horses and sheep a hot manure. But a heap can get too hot — fire-fanged — or mouldy, and when in this state its virtue is destroyed, for the germs on which fermen- tation depends are killed. When fermentation is slow, dung-heaps are turned over so as to allow access of air, but there is a loss of nitrogen in doing so. It will be recol- 'lected that it was stated that urine contains urea, and by fermentation this is changed into a volatile substance and lost. Now this loss takes place chiefly in the first few days, while the manure is in the stall. The loss may be diminished by the liberal use of litter, spent tan, sawdust, or peat moss, or by sprinkling dry earth, powdered gypsum, or marl, especially under cover. Moss litter makes a hot manure, though not so hot as straw, but it has the advan- tage of being obtainable in a dry powdery condition, and can be drilled. Qup:stions. — 1. What is ta general manure? 2. Distinguish between horse, cow, sheep, and pig dung. 3. What changes does farniyard manure undergo ? 4. What are the nianurial substances of value in straw, urine, and dung? How may any of these be lost to the farmer? 5. Give the percentage com- position of farmyard manure in respect of nitrogen, phosphoric acid, potash, organic matter, antl water. Which of these improve the texture of both clay and sandy soils ? 6. Under what con- ditions is the most valuable farmyard manure produced, and how would you regulate its fermentation ? CHAPTER XLVII. COMPOSITION AND EFFECT OF FARMYARD MANURE. 392. Farmyard manure is universally esteemed as a fertiliser by practical men for the following reasons : (1) For its general composition, as it contains all the constituents of plant-life. COMPOSITION AND EFFECT OF FARMYARD MANURE. 237 (2) Because it can be applied to all soils, and crops respond to farmyard dung which will not be affected by artificial fertilisers. (3) For the reactions of decomposing matter in the dung, which benefits the soil chemically and physically. (4) For dung has a cumulative fertility — that is, it lasts long by giving plant-food slowly, and not all at once. (5) It has the power of liberating this store of plant- food when wanted — active in summer, latent in winter. (6) The mechanical effect on the soil is beneficial, and can be controlled. 393. Short and well-rotted dung is applied to light and open soils. In this state the ingredients are available to the plant, so that the crop can make use of it when wanted ; and it also has the effect of making the land firmer and less permeable by water — in fact, more retentive. Long and fresh or green manure is better suited for stiff soils. The long fresh straw opens up the soil, promotes oxidation, and makes it more Avorkable, while the soil itself is able to retain the products of decomposition as tliey may take place. Voelcker recommends that manure should be spread on the land, and the rain will wash the soluble matters into the soil. The objection raised to this is, that fer- mentation of the manure will not take place so rapidly after the manure is ploughed in, owing to its soluble nitrogenous compounds having been washed out, and in many cases lost. 394. Drainings from manure-heaps and urine are valuable, and should be stored in tanks. Stable, cowshed, and heap should all drain into a manure tank. Liquid manure — that is, the drainings or washings from manure — has less nitrogen than urine, but it contains phosphates which urine has not, and when diluted with an equal bulk of water, loses little valuable matter by evaporation. 238 PRINCIPLES OF AGRICULTURE. 395. The quantity of manure that can be obtained depends largely on the amount of indigestible matter in the diet — that is, practically on the food and litter given. Warington gives some data in the following table : PER 100 POUNDS LIVE-WEIGHT PER WEEK. Total dry food re- ceived by the animal. Results ijroduced. Dry manure produced (solid excrement and urine exclusive oC litter). Food used for heat and worlc. increase in live- weight. Oxen. . Sheej). Pigs.. 12-5 lb. 160 H 27-0 - 4-56 lb. 5-10 „ 6-27 n 6-86 lb. 9-06 „ 12-58 H 1-13 lb. 1-76 n 6-43 „ If an animal voids 12 lb. of dung, 8 lb. of litter may be assumed, and we get 20 lb. of dry manure, to which add 60 lb. of water, and we have 80 lb. of wet manure per day, or a ton per month. As the excrements of cattle and pigs are more watery than those of sheep and horses, the former require a larger proportion of litter. The chemical com- position of food is only a partial guide to manurial value, as more depends on the extent to which each constituent of the food is digestible, upon the nature of the other foods given, and on the kind of animal. 396. The worth of the litter used in making farmyard manure depends on two factors. First, its power of retain- ing water, as shown in the following table : WATER RETAINED BY 1 PART OF LITTER. {Warington.) Dead leaves 2'0 Straw 2-2— 3-0 Peat moss 3 '8 Sawdust 4-2-4-4 Spent tan 4-0 — 5*0 Peat 5-0— 8-0 Second, upon the manurial value of its constituents. COMPOSITION AND EFFECT OF FARMYARD MANURE. 239 MANUBIAL CONSTITUENTS IN 100 PARTS OF LITTER. ( Warington.) Nitrogen. ^^'^iJ^^"^ Potash. Dead leaves 08 03 0-3 Straw 0-4— 0-6 0-2— 03 OG— 1-6 Peat moss 08 trace trace Sawdust 0-2— 0-7 0-3 07 Spent tan 0*5 — rO Peat 1-0— 2-0 397. The feeding of animals on the land is an advan- tageous form of applying manure — sheep-feeding being a well-known instance. The advantages are, that animal manure free from a great bulk of litter is more immediately available for the use of plants, and not in the form of little or slowly soluble compounds. The disadvantages are, irregular distribution of the manure, and loss by drainage during winter or a rainy season. Questions. — 1. Why is farmyard manure generally esteemed ? 2. Is the feeding of animals on land advantageous ? 3, What effect has food, condition, and age of animal on manure? 4. What chemical changes take place in the fermentation of the manure-heap, and how does tlie construction of the heap influence the fermentation and the value of the manure? CHAPTER XLVIII. food in relation to manure. 398. The dung and urine are of the utmost importance to the farmer, as they constitute his chief manures. The only constituents of food that are of manurial value are the nitrogen and ash constituents ; hence, if the live-weight of an animal remain unchanged, and there is no production of milk, the quantity of nitrogen and ash constituents in the dung and urine will be exactly the same as that 240 PRINCIPLES OF AGRICULTURE. contained in the food, because the repair of tissues will be exactly equivalent to the amount worn out. If, how- ever, the animal is either growing, increasing in weight, or giving milk, the Aveight of nitrogen and ash excreted must be less than the weight supplied in the food. A fattening ox or sheep stores up as much as 5 per cent, of the nitrogen of the food in the form of increased weight of flesh, consequently over 95 per cent, of it appears in the solid and liquid excrement. A pig, being fed on more digestible and concentrated food, increases in weight much more rapidly, and would store 15 per cent, of the nitrogen, leaving about 85 per cent, in the excrement. 399. If the food is of average digestibility and quality, the urine will contain 75 per cent, of the nitrogen and 95 per cent, of the potash ; while the solid excrement will contain 80 per cent, of the phosphoric acid, 90 per cent, of the lime, and 70 per cent, of the magnesia. Both the liquid and solid excrement of sheep contain much less water than the excrements of oxen and pigs, and are therefore more concentrated. 400. It should be remembered that urea very soon decomposes on exposure to the air, giving off ammonia gas very rapidly; the urine should therefore be apjolied to the soil as soon as possible ; there the nitrogen soon forms nitrates, and thus becomes the favourite nitrogenous food of plants. If the urine cannot be applied at once to the soil, the ammonia should be prevented from flying away by the use of dilute sulphuric acid, solution of proto- sulphate of iron (green vitriol), or gypsum, whereby sul- phate of ammonia, which is non-volatile, will be formed. 401. The following table gives the quantities of nitrogen, potash, and phosphoric acid (fertilising constituents) con- tained in 1000 parts of ordinary cattle food. The value of farmyard manure depends greatly on the feeding of the animals that has made it. An animal may consume a FOOD IN RELATION TO MANURE. 241 hundredweight of molasses, but the manure produced is worth next to nothing : but if the animal eats a hundred- weight of linseed-cake, then the undigested constituents which will pass out of its body will possess manurial value. MANURIAL CONSTITUENTS IN 1000 PARTS OF ORDINARY CATTLE FOODS. {Wariugton.) Drv ^^^^' ,Mr.ffl^ Nitrogen. Potash, plioric matter. ^^^^^ Cotton-cake (decorticated).. 91 8 70-4 15*8 SO'o Rape-cake 887 50-5 IS'O 20-0 Linseed-cake 883 43*2 12-5 16-2 Cotton-cake(undecorticated)878 33 '3 20-0 227 Linseed 882 32*8 lO'O 13-5 Pahn-kernel meal (English). 930 25-0 5-5 12-2 Beans 855 40-8 129 12-1 Peas 857 35-8 10-1 8*4 Malt-dust 905 379 208 18*2 Bran 860 232 15-3 269 Oats 870 20-6 48 6*8 Rice-meal 900 19-1 6-1 238 Wheat 877 187 52 79 Rye 857 176 58 8-5 Barley 860 17*0 4-7 7-8 Maize 890 16'6 3-7 57 Brewers' grains 234 7 8 4 3 9 Clover hay 840 197 186 5*6 Meadow hay 857 15-5 16-0 4-3 Bean-straw 840 13-0 19-4 2*9 Oat-straw 857 6-4 16*3 2*8 Barley-straw 857 5-6 107 1-9 Wheat-straw 857 4*8 6-3 2-2 Potatoes 250 3-4 5-8 1-6 Swedes 107 2-2 2*0 0-6 Carrots 140 2'1 3*0 I'l Mangels 120 1-8 4-6 07 Turnips 80 1-6 2-9 O'S P 242 rRINCIPLES OF AGRICULTUBE. 402. TABLE SHOWING THE DATA, THE METHOD, AXD THE VALUE OF CATTLE FOODS AFTER CONSUMPTION, Fattening In- crease in Live weight (Oxen or Sheep). Description of Food Food tol In- crease. Linseed Liuseed-eake.. . . Decorticated . . ) cotton-cake . )" Palin-nut cake . . Uiidecorticated \ cotton-cake . . ) Cocoa-nut cake . . Rape-cake Peas Beans Lentils Tares (.seed) Indian corn Wheat Malt Barley Oats Rice-meal Locust-beans Malt-coMibs Fine jjollanl Coarse pollard. . . Bran Clover hay Meadow hay .... Pea-straw Oat-sti-aw Wlieat-straw .... Barley-straw. . . . Bean-straw Potatoes Carrots Parsnips Swedi.sh turnips. Mangel-wurzels.. Yellow turnips. . White turnips... . In Fattening Increase (at 1 27 per cent). 8-0 (10) 14-0 1.5 •() 160 lS-0. 21-0 '23-0 2-2 -0 00-0 85-7 75-0 109-1 9(5 133-3 150 In- crease per ton of Food. lb. 448-0 373-3 344-6 320-0 280-0 280-0 (224) 320-0 3-20-0 320-0 320-0 311 1 311-1 3-20-0 311-1 298-7 298-7 248-9 280-0 29S-7 •280-0 248-9 160-0 149-3 140-0 1-24-4 106-7 97-4 101-8 37-3 26-1 29-9 20-5 23-3 16-8 14-9 7o 3-60 4-75 6-60 2-50 3-75 3-40 4-90 3-60 4-00 4-20 4-20 1-70 1-80 1-70 1-65 2-00 1-90 1-20 3-90 2-45 2-50 2-50 2-40 1-50 1-00 0-50 0-45 0-40 0-90 0-25 0-20 0-22 0-25 0-22 0-20 0-lS lb. 80-64 106-40 147-84 56-00 76-16 109-76 From 1 ton of Food. Ih. 5-69 4-74 4-38 4-00 3-56 3-56 2-84 80-64 89-60 94 08 94-08 38-08 40-32 38 08 36-96 44-80 42-56 26-88 87-36 54-88 56-00 56-00 53-76 33-60 22-40 11-20 10-08 8-96 20 16 5-00 4-48 4-93 5-60 4-93 4 -48 4-03 Per cent. of total con- sumed. 4-06 4-06 4-06 4-06 3-95 3-95 4-06 3-95 3-79 3-16 3 -.56 3-79 3 -.56 3-16 2-03 1-90 1-78 1-58 1-36 1-24 1 29 0-47 0-.33 0-38 0-26 0-30 0-21 0-19 7o 7-06 4-45 2-96 7-25 4-24 4-67 2-59 5-03 4-53 4-32 4-32 10-37 9-80 10-66 10-69 8-46 8-91 11-76 4-08 6-91 6-35 5-64 3-78 5-C5 7-95 14-11 13-49 13-84 6-39 8-39 7-37 7-71 4-64 6-0-) 4-69 4-71 Total Nitro- remani- gen ing for 6(1 ual Man- Am- ure. monia. lb. lb. 74-95 91-0 101-66 123-4 143-46 174-2 51-94 03-1 80-44 97-7 72-60 88-2 106-92 129-8 76-58 93-0 85-54 103-9 90-02 109-3 90-02 109-3 34-13 41-4 36-37 44-2 34-02 41-3 33-01 401 41-01 49 -8 38-77 47-1 23-72 28-8 83-80 101-8 51 -09 62 52 -44 63-7 52-84 64-2 51-73 62-8 31-70 38-5 20-02 25-0 9-62 11-7 8-72 10-6 7-72 9-4 18-87 22-9 5-13 6-2 4-15 5-0 4-55 5-5 5-34 6-5 4-63 5-6 4-27 5-2 3-84 4-7 1 Value of Am- monia at 6d. per lb. £ s. d. 2 5 6 3 18 4 7 1 1 11 7 2 S 10 4 1 4 11 2 6 6 2 11 11 2 14 8 2 14 8 9 2 1 8 1 4 11 3 6 14 5 2 10 11 1 11 1 11 10 1 12 1 1 11 5 19 3 12 6 5 10 5 4 4 8 11 6 3 1 2 6 2 9 3 3 2 10 2 7 2 4 FOOD IN RELATION TO MANURE. 243 RESULTS OF THE ESTIMATION OF THE ORIGINAL MANURE SUPPOSING IT EXERCISED ITS FULL THEORETICAL EFFECT. PHOSPHORIC ACID. POTASH. In Fattening In Fattening In Food. Increase at In Food. (0-80 percent.) (0-11 cei per t.) original Manure value Per Total Per Total per ton of Food From cent. re- Value Value Per Per Iton of main- Per Per Iton of main- at sumed. cent. ton. of total ing for per lb. cent. ton. of total ing for 2^d. per lb. Food. con- Man- Food. con- Man- sumed. ure. sumed. In ure. % lb. lb. 7o lb. S. d. 7o lb. lb. lb. s. a. £ S. d. 1-54 34-50 3-85 11-16 30-05 7 S 1-.37 30-09 0-49 1-00 30-20 3 2 19 5 2 00 44-80 3-21 7-17 41-59 10 5 1-40 31-30 0-41 1-31 30-95 6 5 3 18 3-10 09-44 2-90 4-26 00-48 16 8 2-00 44-80 38 0-85 44-42 9 3 5 13 1-20 26-88 2-75 10-23 24-13 0-50 11-20 0-35 313 10-85 2 3 1 19 10 2-00 44-80 2-41 5-38 42-39 10 7 2-00 44-80 031 0-09 44-49 5 11 3 5 4 1-40 31-3G 2-41 7-68 28-95 7 3 2-00 44-80 0-31 0-09 44-49 9 3 3 7 2 fjQ 5(5-00 1-93 3-45 54-07 13 6 1-50 33-00 0-25 0-74 33-35 11 4 5 4 5 4 0-85 19-04 2-75 14-44 10-29 4 1 0-90 21-50 0-35 1-03 21-15 2 15 rio 24-04 2-75 11-10 21-89 5 6 1-30 29-12 0-35 1-20 28-77 3 3 5 0-75 10-80 2-75 10-37 14-05 3 6 0-70 15-08 0-35 2-23 15-33 3 2 3 14 0-80 17-92 2-75 15-35 15-17 3 9 0-80 17-92 0-35 1-95 17-57 3 8 3 2 1 0-60 13-44 2-68 19-94 10-70 2 8 0-37 8-29 0-34 4-10 7-95 \ 8 15 1 9-8r, 19-04 2-08 14 08 10-30 4 1 0-53 11-87 0-34 2-80 11-53 2 5 18 7 0-80 17-92 2-75 15-35 15-17 3 9 0-50 11-20 0-35 3-13 10-85 2 3 16 8 0-7 r, 10 80 2-08 15-95 14-12 3 6 0-55 12-32 0-34 2-70 11-98 2 1 6 1 0-GO 13-44 2-57 (19-1-2) 10-87 2 8 0-50 11-20 0-33 2-94 10-87 2 3 1 9 10 (0T,(») (13-44) (191-2);(10-S7) (2 8) (0-37) (8-29) 0-33 (4-00) (7-90) (1 8) (I 7 10) 2-14 0-27 2-(»0 44-80 2-41 5 38 42-39 10 7 2-00 44-80 0-31 0-09 44-49 9 3 3 10 9 2<>0 04-90 3-90 02-39 15 7 1-40 32-70 0-33 1-01 32-37 6 9 2 13 4 3-50 78-40 2-41 3-07 75-99 19 150 33-00 0-31 0-92 33-29 6 11 2 17 9 3-uO O-.'iT 80-64 214 2 05 78-50 19 8 1-45 32-48 0-27 0-83 32-21 6 8 2 IS 5 12-77 1-38 10-81 11-39 2 10 1-50 33 00 0-18 0-54 33-42 7 2 13 0-40 8-90 1-28 14-28 7-08 1 11 1-00 35-84 10 0-45 35 08 7 5 18 7 O-Sh 7-84 1-20 15-31 0-04 1 8 1-00 22-40 0-15 0-07 22-25 4 8 18 10 0-24 5-38 1-07 19-89 4-31 1 1 1-00 22-40 14 0-03 22-26 4 8 11 7 0-24 5-38 0-92 17-10 4-40 1 1 0-80 17-92 0-12 0-07 17-80 3 8 10 1 0-18 4-03 0-84 20-84 3-19 9 100 22-40 Oil 0-49 22-29 4 8 10 1 0-30 0-72 0-88 13 10 5-84 1 5 1-00 22-40 0-11 0-49 22-29 4 8 17 7 0-1.5 3-30 0-32 9-52 3-04 9 0-.55 12-32 0-04 0-32 12-28 2 7 5 09 2-02 0-22 10-89 1-80 5 28 6-27 0-03 0-48 0-24 1 4 4 3 0-lt> 4-2(i 0-20 0-10 4-00 1 0-30 8-00 0-03 0-37 8-03 1 8 5 5 0(5 1-34 0-18 13-43 1-10 4 0-22 4-93 0-02 0-41 4-91 1 4 7 0-07 1-57 0-20 12-74 1-37 4 0-40 8-90 0-03 0-34 8-93 1 10 5 (0-06) (1-34) 0-14 (10-78 (1-20) (0 4) (0-22) (4-93) 0-02 (0-34) (4-91) (1 0) (0 3 11) 0-0,'i 1-12 0-13 11-01 0-99 3 0-30 0-72 0-02 0-30 0-70 1 5 4 244 PRINCIPLES OF AGRICULTURE. 403. The imexliausted value of farmyard dung is a subject in which every farmer is interested. We know that some of the plant ingredients are readily taken up, others pass freely out of the soil, and some are temporarily changed into an inert or dormant condition. Sir J. B. Lawes of Rothamsted, and Sir J. Henry Gilbert have drawn up a table (402) which gives the proportion retained by the animal, and the proportion voided in manure of the fertilising ingredients in feeding substances. Some of the points to be considered are the age and condition of the animal, and the food given (of course, money value of food is always changing). Then comes the management, loss which takes place in fermentation, and further loss which may have taken place in storage or application. All these factors will give data to guide us in considering the tendency of the fertilising ingredients to pass out of the soil. Having assumed this, the next point is to value unexhausted residues by discounting — according to lapse of time, system of cropping and farm management — the original value of the dung (or consumed food) when made and applied. Questions. — 1. What considerations determine the value of animal excreta as manure ? For what nianurial substances are the solid and liquid excrement respectively most valuable? 2. What do you understand by ' unexhausted ' manures ? 3. How can volatile substances in manure and urine be best retained ? CHAPTER XLIX. OTHER GENERAL MANURES. 404. In this chapter we shall speak of a number of sub- stances which, like farmyard manure, contain all the materials which plants require from the soil. Most animal and vegetable substances are of this character. We will first consider green-crop manures. Mustard, rape, turnips, OTHER GENERAL MANURES. 245 Vetches, and lupines are frequently grown for the simple purpose of being ploughed in, while green, to improve the soil. While growing, they gather mineral matter, nitrogen^ and water from the soil, and carbon and some little nitrogen, in the form of ammonia, from the air. When ploughed in, they therefore enrich the soil only by the little nitrogen and carbon they gathered from the air. But the mineral matter is returned in a much better form for the ready supply of the next crop than it was in for them. They also add humus to the soil, and so greatly improve light land; and the liumic and carbonic acids which are set free in the soil by the decay of the humus, enable the water to dissolve more dormant mineral matter. Green manures are even more bulky than farmyard manures, for they contain more than 80 lb. of water in each 100 lb. ; hence they render stiff soils more open, and so improve their texture. If grown in autumn, they use up the nitric acid which is so rapidly formed in the soil at that season, and so prevent its being washed through by the autumn and winter rains, and preserve it for the use of the suc- ceeding crop. It is generally considered, however, that as meat and milk fetch the farmer such good prices in the market, it is more profitable to apply these crops as manure in a second-hand way, by first using them as food for stock. 405. Green manuring is a simple way of improving a soil deficient in organic matter, especially in hot climates. The characteristic advantage of green manuring lies in the humus added to the soil, and another factor is that vegetable matter rots readily in the green state. Plants grown should be ploughed in when the flower has just begun to open, and not when the seed has formed. For this purpose, in the United Kingdom, buckwheat, rye, winter tares, clover, and rape are sown. In the United States the clover crop is ploughed in, or the first crop cut, and the second ploughed in. On the poor lands of the northern states, Indian corn 246 PRINCIPLES OP AGtllCULTUIlE. is ploughed in ; in Italy, the second or third crop of lucerne. In Tuscany, the white lupin ; in France^ the bean, vetch, and clover; in Germany, borage, and the spurry on the sandy soils of Holstein, are all ploughed in. The best result is obtained by green manuring with leguminous crops, as then, in addition to the organic matter, the soil gains nitrogen which these crops have drawn from the air. 406. The organic manures which we shall note in this chapter may be divided into two classes — vegetable and animal. Vegetable manure serves three purposes. First, it loosens and opens the land. Second, it supplies nitro- genous food to the growing plant. Third, it yields saline and earthy matters in a state fit to be taken up by plants. Near the sea-coast, seaweed can often be obtained for the mere trouble of collecting it ; and if ploughed in while fresh, it is very much like green manuring. Its manurial value is generally reckoned as equal to that of farm- yard manure. When in a dry condition, it contains from 1 to 3 per cent, of nitrogen, about 3 per cent, of potash, and a half per cent, of phosphoric acid. Seaweeds decompose readily, and the value depends on the different varieties of weed in the heap. Some are richer than others. On the south-east coast of Fifeshire, in Kent, the Lothians and the south-western counties of Scotland, it is much used. It is a favourite manure for potatoes in Ireland, and the famous red-soil potatoes of Dunbar are raised on soils manured with seaweed. Seaweeds reduced to ashes con- stitute kelp, which is a good general manure, especially for potatoes. Kelp contains from 20 to 40 per cent, of potassium salts, and 3 to 8 per cent, of calcium phosphate. *Driftweed' contains less potash than 'cut- weed.' 407. Straw has little manurial value unless well rotted, and as it ferments with comparative difficulty, it is usually mixed with some substance that ferments readily — urine or droppings of cattle. Sawdust makes a poor manure ; it OTHER GENERAL MANURES. Uf is sometimes used charred or saturated with liquid manure. Bran, brewers' grains, and malt-dust or combings are used as manures, but it is foolish to do so, as they are useful foods. As manures, brewers' grains are poor in nitrogen, potash, and phosphoric acid. Bran contains half a per cent, of nitrogen and phosphoric acid, and a little more potash, while malt-dust contains 3 to 4 per cent, of nitrogen, about 2 per cent, of phosphoric acid, and slightly more of potash. Peat and tanners' bark are vegetable substances like straw, difficult to work up, but good in a compost heap. Leaves of trees, coal-dust, and charcoal are all used as manures. In some soils, leaves produce sourness owing to the quantity of organic acid formed during decomposition ; generally they contain from '6 to 1 per cent, of nitrogen, *! to '3 per cent, of potash, and *! to •4 per cent, of phosphoric acid. 408. Oilcakes are sometimes used as manures, and are very valuable ones too ; but they are also such nutritious foods that it is much more profitable to use them first of all as foods; they will then, in the second place, enrich the manure-heap. The oilcake made from rape-seed is not much relished by cattle, so that it is cheaper than other kinds, and may be used profitably as a manure. These substances are more valuable for the nitrogen which they contain than for the mineral matters. 409. Peruvian guano is a very powerful general manure, and one of the most valuable concentrated manures that can be obtained. It is particularly rich in nitrogen and phosphoric acid. It consists of the dried dung of sea-birds, which has accumulated in the course of centuries to a great depth on the coast of Peru, in South America. It is an excellent form of top-dressing for corn or grass crops. Guanos are divided into two classes — viz. (a) those contain- ing nitrogen, and (h) those of a purely phosphatic nature. Nitrogenous guanos can only be formed in rainless districts. ^48 PRINCIPLES OF AGRICULTURE. Each of these two kinds of guanos wc will notice fuller in our chapters on phosphatic and nitrogenous manures. 410. Dried blood and fish are good general manures ; the former containing the mineral matters which make bone, as well as the nitrogenous substances which form lean ; and the latter being really that of which guano was formed, for the sea-birds who deposited the guano lived on fish. The flesh, or carcasses of animals, is equal to blood as a manure. A carcass weighing 500 lb., besides organic matter, will give about 12 lb. of ammonia and 24 lb. of bone phosphate ; and dried blood contains 9 to 12 per cent, of nitrogen. Hides, horns, hoofs, hair, and feathers are rich in nitrogen, containing from 15 to 17 per cent. If means are not adopted to hasten their decomposition, they will remain years in the soil undecomposed. Fish guano, made in Norway and the United States from fisli offal, is very insoluble and slow in decomposing owing to the amount of oil present. Animal guano, or meat-meal, is more active than fish guano. It is the refuse and remains of animals used in beef extract and tinned meat works, and is largely manufactured in South America, Australia, and IS^ew Zealand. There are two kinds — some nitrogenous, contain- ing from 11 to 13 per cent, of nitrogen ; others phosphatic, containing from 14 to 19 per cent, of phosphoric acid. To apply the word ' guano ' to dried meat and fish is not strictly correct, because guano is a corruption of the Peru- vian word huano, dung — the excreta of a bird or animal. 411. Woollen rags and woollen wastes, such as the * shoddy ' of the cloth factories, aie used as manures, and are mainly valuable for the nitrogen they contain. They might therefore be classed along with hides, horns, hoofs, and hair, among the special nitrogenous manures. Woollen rags and wastes are very slow in decaying, and therefore yield up their nitrogen very gradually ; but they are last- ing, and are often used as hop manures. Wool is also a OTHER GENERAL J^IANURES. 249 substance rich in nitrogen. Some varieties contain very large proportions of a peculiar fatty matter termed sidntj ■which is rich in potash. Eaw merino wool contains from one-fourth to one- third of its av eight of suint. 1000 lb. of raw merino wool yield from 70 to 90 lb. of potassium carbon- ate, and from 5 to 6 lb. of potassium chloride and sulphate. Questions. — 1. What are nianiires, general manures, special manures, natural manures, and artificial manures? 2. Enum- erate the general manures, and indicate their values as supplying plant-food and improving the texture of the soil. 3. What is green manuring, and what is its use and value ? 4. Name some vegetable and animal manures, and state their value. CHAPTER L. PHOSPIIATIC MANURES. 412. We now commence the consideration of special manures — that is, those that are applied for the purpose of adding certain special substances only to the soil, and not all those required by crops. As already explained, phosphoric acid requires special application more generally than others, because it is never plentiful in the soil, and yet is largely carried quite away in the grain, bones, or milk that are sold off a farm. 413. We will start from what we know already— namely, that bones consist mainly of phosphate of lime. But there are three phosi)hates of lime — tricaldc 'phosphate, or three- limed phosphate ; dicalcic j^l^ospliate (also called bicalcic phosphate), or two-limed phosphate ; and monocalcic phos- phate, or one-limed phosphate. The first of these is the one which occurs in bones, and is not at all soluble in water ; the second is very slowly soluble ; and the third, which is called superphosphate, is very readily soluble. The following table will perhaps make this matter clearer : 250 PRINCIPLES OF AGRICULTURE. Base. Acid. Salt. -J. . / + iPliospholic Acid = Tricalcic, or insoliiLle bone -J. . I phosphate. J . / + Phosphoric Acid = Dkalcic, or very slowly soluble Water ) phosphate. " / + Phosphoric Acid = Monocalcic, or very soluble ^l^ll j 5?/i^cr-pliosphate. From it will be seen that phosphoric acid requires three equivalents of base, either lime or water, to form any of the three calcium salts; and it will also explain why the last is named sw^:>er-phosphate — namely, because the proportion of phosphoric acid to lime in it, is much greater than in ordinary phosphate. 414. Bone phosphate was the only one used at one time ; the bones were broken into pieces called half-inch bone, and when spread on the land, were very slowly dissolved by the carbonic acid of the rain, before they became suitable for plant-food. If, however, raw bones, which have had the fat first removed from them by steaming, are ground into bone-meal, and applied to the soil, good results are apparent much sooner, because the phosphate of lime is more diffused through the soil; and, being in a fine state of division, is much more quickly made soluble for plant use. Raw bones also contain much organic matter, which will yield nearly four per cent, of nitrogen. Extracted bones — that is, bones whose oil has been ex- tracted by steaming — show a high percentage of phosphoric acid. Commercially, bones for manure are sold as half- inch bones, quarter-inch bones, bone-meal, bone-dust, and bone-flour. Other forms are fermented bones, dissolved bones, bone ash, and bone black. 415. Since bone phosphate was first applied to the land, large stores of tricalcic phosphate have been discovered in phospSatic manures. 261 various parts of the world as minerals, in the form of fossils or pebbles called coprolites, and of rock called apatite and phosphorite. The first mineral phosphate to come into use was Cambridgeshire coprolites from the Upper Greensand of England. Then other deposits of coprolites, but of in- ferior quality, were discovered in the Lower Greensand and Tertiary, and in France, of rock or crust guanos in many parts of the West Indies, of apatite in Canada and ISTorway, of phosphorite spar in Spain, of the Nassau phosphate in Germany, of large deposits of phowsphatic nodules in South Carolina, of still larger deposits of various qualities in Florida, of large, but low quality, deposits in Russia, and recently of deposits of great extent and value in Algeria. These mineral phosphates are very hard, but if ground to powder and applied to soils which contain much humus — old meadow or peaty land — they are gradually dissolved by the humic and carbonic acids which the decay of the humus produces, and prove most valuable manures. The average amount of phosphoric acid in these mineral phosphates is : Phos. Acitl, In Per cent. Phosphorite, Spanish.. 20 to 42 Carolina phosphate 25 m 27 Florida rock phosphate 32 i. 87 Florida river phosphate 25 n 30 Algerine phosphate 28 n 32 Phos. Acid, In Per cent, Cambridge coprolites. , , 26 to 28 French phosphates 17 n 38 Belgian phosphate 10 n 28 Ptock gnano 30 ., 40 Apatite 30 .. 42 Phosphatic rock is broken by hammers or stone-breaking machinery, then ground to a fine powder by various l + Phosphoric Acid Lime ) = Tricalcic Phosphate. Water \ ^ /Sulphuric Acid ) Water ] I Sulphuric Acid t Oil of Vitriol (True Sulphuric Acid). Linie j Water > + Phosphoric Acid Water ) = Monocalcic Phosphate. PHOSPHATIC MANURES. 253 water in return ; and the result is, a mixture of monocalcic l»hosphate and sulphate of lime, which is the superphos- phate of the manure manufacturer. The change can be illustrated by the use of chemical symbols. Tricalcic pliosphate is (CaO)3P205, or CagPgOg, and sulphuric acid is represented by H.^SO^, or HgOSOg. Two parts of sulphuric acid to one of phosphate is taken, and we can show it thus: Tricalcic , Sulphmic Phosphate. "^ Acid. CaO. HsOim i£b y (•■■pY>^\|-^^^«^ } '^'^3 CaO CaO } ^03 CaH4P208, , Monocalcic + -»-ar5U4, Phosphate. Gypsum. 417. Now, monocalcic phosphate is a very acid salt — perhaps too acid for the immediate use of plants ; but it has been found that, being soluble, it easily gets diffused in the soil, but cannot remain soluble long, for either lime, iron, or alumina will take the place of the M'ater, and reduce it to a less soluble state. A great many experiments have shown that a mixture of bone-meal, or ground mineral phosphate with superphosphate, produces a much, healthier growth and better yield than superphos- phate alone, and is much cheaper; the price of superphos- phate being about double that of the tricalcic phosphate. By thus mixing the most soluble and least soluble phos- phates together, a more natural and lasting plant-food is produced, resembling the middle or slowly soluble phos- phate, produced by the action of the very weak carbonic acid on the tricalcic phosphate in the soil. The superphos- phate produced from bones is generally called ' dissolveci 254 PRINCIPLES OF AGRICULTURE. bone,' to distinguish it from 'mineral superphosphate.' The mixed phosphate may be called 'reduced superphos- phate.' When a soluble phosphate has 'gone back/ and lost its original character,, it is termed 'reduced,' or 're- verted,' and has an agricultural value between soluble and undissolved phosphates. 418. Phosphatic manures produce a wonderful effect upon root-crops, which come once in a rotation ; and as tliese are eaten on the farm, a great deal of the phosphoric acid is returned to the land, in a suitable form, for the use of the corn-crops which follow. These, in the last stage of their growth, take nearly all the phosphoric acid which they have gathered from the soil, up into tlie seed. It is therefore a seed-forming manure, and favours early maturity in corn-crops. The activity of the various phosphates is influenced by climate. In a dry warm season if is found that finely ground bones, guano, ground rock guano, and several kinds of phosphates, such as Cambridge coprolites, Carolina and Algerine phosphates, produce a good effect on all root and cereal crops. In a wet and cold season, or on cold or heavy soils, the effects of insoluble phosphates are not so favour- able, and better results are got from soluble phosphates. The activity of Thomas phosphate powder is intermediate between soluble phosphate and ground mineral phosphate, it being decidedly more active than well-ground bone-meal. Some kinds of phosphates act so slowly in the undissolved state as to be practically useless, unless on some soils of special composition. To this class belong Eodonda and Alta Vela phosphates, in which the ]ihosphoric acid is combined with alumina, and nlso apatite, a crystalline form of phosphate of lime, and the Florida phosphates. The soils on which superphosphate gives the best results are the 'lime' ones, and it is used chiefly for turnips nnd the corn- crops, especially barley. PHOSPHATIC MANURES. 255 419. Some phosphates, finely ground, are used as man- ures, and the most suitable for this purpose are Thomas slag and phosphatic guanos. Thomas slag is a material sometimes called ' basic cinder,' ^ basic phosphate,' 'basic slag,' or 'Thomas phosphate,' and is a phosphatic manure which has come very largely into use in the last few years. It is a residual material obtained as a bye-product in the manufacture of steel from phos- phoric pig-iron. The phosphorus of the iron, which would otherwise render the steel made from it unfit for most purposes, is removed by lining the Bessemer ' converters ' (in which pig-iron is decarbonised) with a coating of lime and magnesia. The phosphorus is converted into phosphoric acid, and attaches itself to the lime; but at the high temperature of the molten metal, it forms, not ordinary or tribasic phosphate, but a phosphate containing more lime and having peculiarly valuable properties. Slag has four parts of lime and one of phosphoric acid. When finely ground, it is found to be remarkably efficacious as manure, the phosphate being far more readily available than mere finely ground ordinary mineral phosphate. It is of various qualities, ranging from about 12 per cent, of phosphoric acid (equal to 26 per cent, of tribasic pliosphate of lime) to over 20 per cent, of phosphoric acid (equal to nearly 44 per cent, of pliosphate). The efficacy of this fertiliser depends largely upon the fineness to Avhicli it has been ground. Of course the phosphates are more insoluble than those in superphosphate, thus taking a longer time to affect the plant, and so requiriug earlier cowing. At the same time the phosphates in basic slag are much more soluble than those in bones, and for a somewhat curious reason. When freshly made, the soluble phosphates in superphosphate are readily solul)le in water. If, however, kept any length of time, a certain portion of them 'go back ' and become, as we have seen, what is know;). 256 PRINCIPLES OF AGRICULTURE. along with other terms as ' jDrecipitated ' phosphates. When mixed with the soil, all the soluble becomes precipitated ])hosphates, as it seems in this form only can the plant assimilate it. In order to, do this, the phosphoric acid combines with a larger amount of lime than it could combine with in its soluble form, so that we have three forms of manurial phosphates — soluble, precipitated, and insoluble, the second containing twice as much, and the third thrice as much lime as the first. In basic slag we have, however, it seems, a form containing four times as much lime, and naturally w^ould consider it to be even more insoluble than bone-meal or the insoluble phos- phates of coprolites, &c. It seems, however, such is not the case, and the attempt to carry more lime than it is able makes it more liable to lose it, and so come into the con- dition of precipitated phosphate. 420. Tlie phosphatic guanos, along with slag, are used direct without being acted on by sulphuric acid. The follow- ing table gives the percentage composition of some of them : PHOSPHATIC GUANOS. Phosphoric In Calcic Acid. Pliosi>hate. Per cent. Per cent. Baker Island 39 85 Enderbury 37 81 Aves 34 74 Sidney Island 34 74 Maiden Island 32 70 Browse Island 31 68 Huon Island 28 61 Superphosphate and dissolved bones, along with other substances which have been acted upon by an acid, are termed acid phosphatic manures, and when free from acid, as in basic cinder, non-acid phosphatic manures. Super- phosphate forms the basis of almost all ' manufactured ' manures, especially what is termed the ' special ' manures^ PHOSPHATIC MANURES. 257 such as turnip and potato manures. Superphosphate made from bones is known as dissolved bones, and shouki be termed bone superphosphate in contradistinction to mineral superphosphate. We must also distinguish be- tween dissolved bones and dissolved bone compound, which is a mixed manure made from mineral superphosphate, with variable quantities of bone, blood, &c. The following analysis shows the difference between a bone and a mineral superphosphate : Mineral Bone Superplios- Superphosphate. phate, or pure dissolved bones. Moisture 1500 12'06 Organic and volatile matters 12-00 32*06* ' Monobasic or nionocalcic phosphate of lime 1800 14-65 Equal to tribasic or tricalcic phos- phate of lime rendered soluble by acid [28-28] [22-94] Insoluble phosphates 600 20-95 Sulphate of lime and alkaline salts.42"50 18*87 Insoluble matters 650 141 100-00 100-00 Questions. — l. From what sources are phosphatic manures obtained? What would be about the percentage of phosphoric acid in a rich soil? Show how it is permanently removed from the farm. 2. Explain what is meant by tricalcic phosphate, superphosphate, and reduced phosphate. 3. What chemical change takes place in the manufacture of superphosphate of lime ? What bases in the soil ' fix ' soluble phosphate, and how do plants succeed in feeding on phosphoric acid when thus fixed ? 4. Of what value is ' bone-meal ' (ground from steamed bones) as a manure? Compare with it phosphorite powder. What crops are specially benefited by the application of phos- phatic manures? Where is the ultimate destination of phos- phoric acid in the plant? 5. AVliat is 'bcisic cinder,' 'reduced phosphate,' 'dissolved bone compound,' 'Baker Island guano,' 'apatite,' and ' mineral superphosphate ? ' * Containing nitrogen 3-09 Equal to ammonia S'Zp Q 258 PRINCIPLES OF AGRICULTURE. 421. PERCENTAGES OF NITROGEN, PHOSPHORIC ACID, AND POTASH IN SOME PHOSPHATES AND MANURES. Manures. Nitrogen. Phosi)horic Acid. South Carolina phosphate.., Belgian n Somme n Estremaduia n Canadian n Aiuba II Curacao n Navassa h Cambridge coprolites , Bedfordshire i Pas de Calais n Seaweed (in dry matter) Fish manure Peruvian guano Ichaboe guano Baker Island guano Maiden Island n Oilcakes Sodium nitrate Sulphate of ammonia Dried hoofs and horns Dried blood Meat-meal guano — Nitrogenous Phosphatic Shoddy and wool waste Soot Fresh bones Steamed bones Bone-ash Basic slag Superphosphate (ordinary). . Superphosphate (liigh class) Muriate of potash. Nitrate of potash...'. Kainite Wood-ashes Coal-ashes Bats' guano Pure dissolved bones Dissolved bone compound... Steamed bone-flour Dissolved Peruvian guano.. Per cent. 1 to 3 7 to 10 2-5 to 9 12 '5 •4 2-5 to 7 15 to 16 20 15 9 to 12 11 to 13 6 to 7 3 to 8 3-5 3-5 1-4 14 2-2 to 2-5 2 5 Per cent. 25 18 33 23 33 to 39 39 40 32 26 24 20 8 to 10 14 to 21 9 34 35 1 -5 to 3 •6 to 3 14 to 17 19 29 34 17 11 to 12 17 4 to 6 *7 13 to 16 13 to 16 25 to 27 11 NITROGENOUS MANURES. 259 CHAPTEE LI. NITROGENOUS MANURES. 422. Most of the general manures which we have noticed are also valuable nitrogenous manures ; but those that we are now going to consider are special manures, bought and applied by the farmer, solely for the nitrogen which they contain. The first is, nitrate of soda, which is brought from Peru and Northern Chili in South America, where it occurs in immense beds many feet thick, and the salt is purified by dissolving and recrystallising it. Being so soluble, it is a very rapidly acting manure, especially on grain and grass-crops ; in a few days, in spring, it Avill change a sickly yellow corn-crop to a dark healthy-looking green. But its effect is greater on the leaf and straw than on the grain ; it is usual, therefore, to mix | cwt. of nitrate of soda with about three times as much common salt, as a dressing for an acre of corn, to prevent a too luxuriant growth of straw at the expense of the grain. This is not so necessary for grass, because it is grown for its leaf and stem, and not for its seed. Nitrate of soda also has a very good effect on mangels and cabbages. It is more easily washed out of the soil by rain than any other manure, and therefore should be applied as a top-dressing to crops while they are in active growth, and able to use it at once, and not during the rainy periods of late autumn and winter. The nitrate of soda of commerce contains from 15 to 16 per cent, of nitrogen, and is valuable solely for its nitrogen. Of all artificial or concentrated manures it is quickest in its action. The usual impurity is common salt. 423. Nitrate of soda is called a plant stimulant, because 260 PRINCIPLES OF AGPtlCULTURE. it gives a plant a sudden activity of growth, which enables it to gather more rapidly from the air and soil the substances which it requires, other than the nitrogen supplied in the nitrate itself. Hence land should be well supplied with those other ingredients that are essential for plant growth in sufficient quantities and in an available condition, before nitrate of soda is applied. This is the reason why nitrates have proved most heneficial tvhen iLsed tuith j^^^osphatic manures. It has been called a 'whip,' and is said to ' scourge ' the land and ' exhaust the soil.' As a matter of fact, it simply supplies a plant-food to the plant, by which the growth is promoted. Nitrate of soda is specially suited for corn-crops and mangels and for clay lands. The following is the analysis of an average sample of nitrate of soda : Moisture 2'59 Common salt - 1*22 Other impurities -36 Pure nitrate of soda * 95 '83 100-00 424. Sulphate of ammonia is another special nitrogenous manure, and is as valuable as nitrate of soda ; it is not quite so rapid in its action as nitrate, but it is not so easily washed out of the soil. It is obtained from the ammonia liquor of gas-works, by mixing Avith it sulphuric acid. It is a special manure, valuable only for its nitrogen and suited for corn-crops, but is best employed mixed with phosphate and potassium salts. It is the most highly nitrogenous of all the concentrated manures, containing 24- 25 per cent, of ammonia or 19 -8-20 '6 per cent, of nitrogen. About I cwt. of sulphate of ammonia contains as much nitrogen as 1 cwt. of nitrate of soda, and it is the nitro- genous ingredient in the ' special ' manures. As it is not * Equal to about Nitrogen 15"5 or Ammonia 19*0 NITROGENOUS MANURES. 261 90 liable to be washed out of the soil as nitrate of sodn, it lias the advantage over nitrate of soda in wet seasons. Sidphate of ammonia should never he mixed with basic slag, because the sulphuric acid in the ammonia combines with the lime in the slag, forming sulphate of lime, and the ammonia then passes off as a gas and is lost. Nitrate of soda can be safely mixed with the slag, but it should not be mixed with superphosphate, as the sulphuric acid in the superphosphate combines with the soda, and the nitrogen passes off as a gas and is lost. On the other hand, sulphate of ammonia can be mixed safely with super- phosphate and most other substances Avith the exception of slag, but it should not be mixed with lime, nor applied to land which has been recently limed. 425. Soot contains a small percentage of sulphate of anmionia; hence its value as a top-dressing for spring corn. Soot also contains from 16 to 40 per cent, of mineral matter. The amount of ammonia depends upon tlie extent to which the soot is mixed with ashes and other refuse. It is regarded sometimes as a stimulant simply because quick in its action ; but it supplies an essential plant-food — nitrogen. 426. Nitrogenous manure can be classed under three heads according as the nitrogen exists in the form of nitrates, as nitrate of soda, or ammonium compounds, as sulphate of ammonia or combined with organic matter, as blood, guano, and offal, and the other organic manures we have noted in a former chapter. These substances are soluble in the following order, the most soluble standing at the head : Fresh urine. Fish-scrap. Dried hlood. Dried offal. Dried and pounded flesh. Coarse hone-meal. Guano. Horn-ineal. Fine bone-meal. Dung. Oilcake. Hair and wool. 262 PRINCIPLES OP AGRICULTURE. 427. The only nitrogenous manure we have still to notice, so as to complete our list, is guano. The composition of guanos at present in use is given in the following table : NITROGENOUS GUANOS. Nitrogc,.. A„„„o„i.. r..»,>horic ^TrMc.c Per cent. Per cent. Per cent. Per cent. Corcovado 11 13 15 33 Saldanha Bay 9 11 9 20 Ichaboe 8 10 9 20 Pabel Ion de Pica 7 9 14 31 PimtadeLobos 4 5 15 33 Huanillos 6 7 13 28 Nitrogenous guano is a highly concentrated manure, and can be used for corn-crops, potatoes, and roots. The nitrogen is chiefly present as uric acid and as ammonium salts. Damp Peruvian gnano is sometimes treated with a small proportion of sulphuric acid, and is then called 'dissolved guano.' These nitrogenous guanos can only come from rainless districts, as the nitrogenous portion becomes washed away where raiu falls. Questions. — 1. What valuable maiuirial substance does nitrate of soda supply to plants ? It is called a plant ' stimulant ' and a soil ' exhauster.' What do you understand by these terms? 2. On what crops is the effect of nitrogenous manures most marked ? Why is salt a])plied with nitrate of soda ? 3. Whence is sulpliate of anunonia obtained? What plant-food is it vahi- able for ? How should nitrate of soda or sulpliate of ammonia be applied ? CHAPTER LIT. POTASH AND OTHER MANURES. 428. Potash is not so much required as a special manure as either phosphoric acid or nitrogen, because it is contained in many soils in sufficient quantity for POTASH AND OTHER MANURES. 263 the wants of most crops ; and also, because it is nearly all returned to the soil year by year in the farmytird manure, especially when the urine is returned. It has, however, in many cases greatly improved the crops of the clover and root classes of plants, which require a great deal of this ash ingredient ; but especially has it been found an excellent potato manure. 429. Nitrate of potash (nitre or saltpetre) is the most valuable of all potash manures, because the nitrogen which it contains, alone makes it as valuable as nitrate of soda as a nitrogenous manure. But this salt is the one chiefly used in the manufacture of gunpowder; and the great demand for it for that purpose causes it to be too expensive for purchase as a manure. 430. The reason why nitrate of potash is mentioned here as a manure, though rarely bought by farmers for that purpose, is, because there are ways in which farmers can produce it for tliemselves roughly. Whenever animal matters (such as clippings of hides, dung, urine, &c.) are mixed with lime and vegetable substances, or earth containing potash, and exposed to the air, nitrate of potash is formed. A look at our table of salts (par. 52) will show that nitrate of potash consists of potash, nitrogen^ and oxygen. The nitrogen is supplied from the animal matters, and some, too, from the vegetable substances; the oxygen from the air; and the potash from the earth, urine, and vegetable matters. The lime combines readily with the nitric acid which is first pro- duced, and then the potash displaces the lime. The potash will not so readily combine with the nitric acid as the lime ; hence the use of the lime to start the com- bination. The growers of early potatoes on the Ayrshire coast, in Scotland, specially bargain for all the potash in their potato manure to be from nitrate of potash. 431. When lime is applied to a soil that has been ^64 t'itlNClPLEg OF AGRICULTURE. heavily manured, and well opened up by tillage for admis- sion of air, the change which has been described slowly takes place; and so this valuable manure, nitrate of potash, is produced in the soil. Careful farmers also collect the clippings of hedges, scourings of ditches, and other like refuse matters, mix them with lime, and form them into what is called a compost heap; by so doing, they are preparing a certain quantity of nitrate of potash, to enrich their land with. 432. There is, however, one material which is cheap enough to be purchasable by the farmer as a special potash manure, and that is kainite. This substance is found in large quantities at Leopoldshall and Stassfurt in Prussia (near Magdeburg), overlying an immense bed of rock-salt at a great depth below the surface of the earth. Kainite consists of chloride of potassium, sulphate of magnesium and water, with the chlorides of sodium and magnesium in addition. It will contain about 13 per cent, of potash. Mr Clement Cadle has proposed that farmers should mix kainite with the farmyard manure as they cart it into the heap ; it will there under- go a gradual change ; the potash will probably combine with the nitric acid produced in the fermentation of the manure, and thus form the valuable nitrate of potash we first spoke of in this chapter; besides which, the sulphates and chlorides have the power of ' fixing ' the ammonia. 433. Potassium chloride, under the name of muriate of potash, has been used as a manure for many years. It is much richer in potash than kainite, and contains 52*35 per cent, of potassium, which is equal to 63'1 per cent, of dry potash. It is obtained as a bye-product in the manufacture of potassium chlorate, of sugar from beetroot, and other manufactures. Potassium sulphate is also obtained as a bye-product in a number of manu- factures, and is used as a potash manure. Wood ashes POTASH AND OTHER MANURES. 265 are also a source of potash, containing between 5 and 10' per cent. Potash manures produce the best result on pasture and leguminous crops; potatoes and root-crops also seem to benefit. On clay soils they have no effect, and are only lil^ely to be beneficial on light soils. Mag- nesium sulphate was formerly introduced by manufacturers into ' special ' manures, but it is not purchased directly as a manure. Though freely soluble, a good soil ^vi\\ retain both potash and magnesia. 434. Common salt (chloride of sodium) is used as a manure for mangels and for mixing with nitrate of soda. Its action in the soil is not understood, but apparently it is both physical and chemical, and resembles in many respects the action of lime. It causes clay particles to coagulate, and helps to set free potash and phosphoric acid in the soil. In certain soils the use of salt leads to the formation of a pan ; and, if present in too large a quantity, will make a soil sterile. 435. Of the manures we have now noted, it may be said that when the three ingredients, nitrogen, phos- phoric acid, and potash, are applied alone, the most favourable results will be obtained when nitrogen is used for cereal crops, phosphoric acid for root-crops, and Ijotash for leguminous crops, and these are termed the dominant manures. Questions.— 1. What is kainite, and for what manurial sub- stance is it valuable ? 2. Is saltpetre a good manure ? 3. What do you know about the muriate of potash ? CHAPTER LIIL LIME. 436. Lime is one of the chief ash constituents of the clover and root classes of crops, and is contained in smaller 266 PRINCIPLES OP AGRICULTURE. proportions in the ashes of all otlier classes of plants; it is therefore a very important plant-food. By a dress- ing of lime, fields have been known to bring forth common white clover, where nothing of the sort had been seen before ; and so lime frequently improves pastures by caus- ing highly nutritious wild plants to spring up for the lirst time. In this way it greatly benefits clay soils that are sometimes deficient in a natural supply of lime, and peaty soils that are also poor in this and other mineral plant-food. Light dressings applied to w^orn-out pastures often quite change their character for the better. 437. And yet, except in the cases just mentioned, lime is not applied to soils so much for the purpose of feeding crops directly itself, as for setting free the dormant plant- food of the soil for their use. We will endeavour to explain the many ways in which it thus liberates these valuable substances. 438. Potash and soda are bound up with silica and other mineral substances in the insoluble rocky particles of the soil, and in this condition are unable to feed plants ; but, as we know, water containing carbonic acid is able very slowly to dissolve the potash and soda out, and so break up the combination; but lime is such a powerful base that it can do this work quicldy ; it turns out the bases, potash and soda, and takes their place. They are thus set free to form compounds with any acids they can find in the soil ; but the compounds which they then form are soluble, and can therefore be absorbed by the roots of plants. Exchanges of this kind are constantly going on in the soil. 439. We said in our last chapter that lime was the active base in combining with nitric acid, but was after- wards replaced by potash, to form nitrate of potash. We have also noted the use of alumina in the soil, to retain potash and ammonia in the loosely-combined form of LIME. 267 double silicates, ready when required to give up potash, ammonia, and silica to the plant. Kow, lime is the active base which generally begins the formation of these double silicates by taking the place of part of the alumina tluit is combined with the silica. But the double silicate of alumina and lime once being formed, the potash or ammonia will easily replace the lime. 440. So lime, by liberating potash and soda from the dormant mineral matter of the soil, and helping to form nitrate of potash, and the donble silicates in the soil, prepares a great deal of important plant-food for the use of all kinds of crops. 441. Eut this is not all ; it is even more destructive to the organic matter of the soil than to the mineral portion, causing it to quickly break up into water, carbonic or other organic acids, and ammonia. So here again it sets free the nitrogen as a plant-food from its dormant state. Lime aids decomposition of silicates, promotes oxidation of vegetable matter, and neutralises liumic acid. 442. The general effect of lime is to render available the plant-food already in the soil. Without itself supplying any significant amount, it will plainly be seen from all this^ that if lime were applied constantly to the land, the land would become gradually exhausted of those substances set free by the lime, and really would be made poorer and poorer. Lime is, therefore, an exhaustive manure. 443. There is another use of lime — namely, that of sweetening sour land, and thereby making it more suitable for the growth of farm-crops. Land is soured by the decay of vegetable matter in a wet state, and the consequent pro- duction of certain organic acids. Lime combines with these acids, thereby forming salts which are not at all acid in character. 444. Now, there are two ways in which all these changes may be brought about by the use of lime — a slow, and a 268 PRINCIPLES OF AGRICULTURE. very quick way. If chalk (carbonate of lime) be used, these changes are all brought about very slowly ; but if quicklime (burnt lime) be applied, they take place very rapidly. Quicklime should never be used in a sandy soil, because it soon destroys the vegetable matter in it, which helps to keep such a soil cool and moist, and to retain soluble manure in it. And even on clay soils, which are natiiralhj retentive of moisture, it should not be used oftener than once every six or eight years ; and the land should at other times be well manured, because of the exhaustive character of the lime. It may be used on peaty soils, as they contain an almost unlimited amount of vege- table matter, and are generally at first sour. It may also be used with advantage on stiff clays, for they are the ones where the double silicates can be formed. It is often used, too, on old pastures when first broken up, to bring the large amount of organic matter, which has accumulated in the course of years, into a serviceable condition for the crop intended to be next grown. Under other conditions, the slowly-acting carbonate of lime only should be applied. 445. When quicklime is to be used for the land, it should be placed in small heaps over the field ; water should then be poured on each heap to slake or crumble the lumps to powder ; the heaps should at once be covered with earth, to prevent, as much as possible, the carbonic acid gas of the air being absorbed ; and it should, without loss of time, be spread over the field, and harrowed in. A better plan is to empty the shells near a supply of water, then cart the slaked, lime to the field and spread it from the cart; by so doing it is much more regularly slaked. Lime has a great tendency to sink into the soil of itself, so should not be ploughed in. If it be exposed to the air, or allowed to remain in heaps for long, it will absorb carbonic acid gas, and a good deal of it will be converted into carbonate of Hme again. LIME. 269 446. There is yet one more important use of lime. It improves the texture of soils, and for this purpose can be used as chalk. Coming, as it does, midway between sand and clay, it helps to make sandy soils more retentive and firm, and clays more ojjen and friable. 447. Marls are frequently used for this purpose ; they are mixtures of clay and chalk, and frequently contain small quantities of phosphoric acid, and other ash ingredi- ents. AVhen containing a large proportion of clay, they aie especially valuable to sandy and peaty soils, both as manures and consolidators. Some marls supply a notable quantity of phosphoric acid, but they are chiefly put on land for the sake of the carbonate of lime they bring. 448. Gypsum, w^hich is made of lime and sulphuric acid, is used as a manure in Germany on grass land, and in the United States for every kind of crop, giving striking results with Indian corn. It promotes the process of nitrification, but its chief value probably lies in the fact that it acts on the potash in the soil, and renders it available for plant requirements. It is of little use on soils containing any large amount of lime, and is unnecessary where superphosphates are used. Gypsum, which is the same material as plaster of Paris, is termed in America as a manure ' land plaster,' and the application of it termed ' plastering.' ' Liming ' land may mean the application to land of quicklime (caustic lime), slaked lime (hydrated or slack lime), or carbonate of lime (limestone and chalk). The rocks called dolomites, or magnesian limestones, contain a large proportion of magnesium carbonate. For agricultural purposes they are of less value than other limestones, as they cannot be applied freely and abundantly to the land, as they possess a burning or scorching quality. 449. Lime, as we have seen, is found in many forms, as earth phosphates (calcium phosphate) in bones and guanos, as carbonates in chalk and hard rock, and as a sulphate in 270 PRINCIPLES OF AGRICULTURE. gypsum. When limestone is burned in a kiln, heat drives off the carbonic acid, and the pure lime is left behind. Pure carbonate of lime consists of Carbon dioxide, Carbonic acid (COg) 44 per cent. Pure lime (CaO) 56 100 If this pure lime (quick or caustic), which has a great affinity for Avater, be slaked by means of water, it heats, emits steam, swells, cracks, and becomes a fine white powder, Avhich consists of Lime 76 per cent. Water. 24 100 As soon as lime is slaked it begins to absorb carbonic acid, and in the course of time is brought back into the mild uncaustic carbonate. If quicklime be left to itself, the same changes take place spontaneously. The advantages of burning lime are partly mechanical and partly chemical : mechanical, as it is obtained as an exceedingly fine powder, which can be spread over a large surface and intimately mixed with the soil ; and chemical, because it is in a more or less active and caustic state, till it absorbs carbonic acid from the air or soil ; till then it is energetic in its action. 450. The quantity of lime to be applied, and the frequency of the dressing, depends on the kind of land, the depth of the soil, the quantity and kind of vegetable matter which the soil contains, and the species of culture to Avhich it is subjected. The caustic or hydrated form of lime is applied (1) to heavy clays, (2) to peaty soils, (3) to any soil which has an excess of vegetable matter, and (4) to soils soured by the presence of poisonous salts of iron or the lower organic acids. Mild lime (chalk, marl, &c.) is applied to light lands poor in organic matter. LIME. 271 The action of lime in a caustic state is to (a) combine with free acids in the soil, and thus to sweeten it. It also (h) decomposes certain compounds of iron, manganese, and alumina in the soil, and renders them unhurtful to vegeta- tion, and (c) liberates compounds of potash, soda, and ammonia, and makes them available. Further, the organic matter in the soil (d) is made to undergo decomposition more rapidly, and (e) nitrogen is made more available, by its conversion into ammonia and nitric acid being promoted. The effects of mild lime are, that (1) it supplies directly a portion of plant-food in such soils as are deficient in it. It neutralises (2) all acid substances formed in the soil — the action of alkali on an acid ; and (3) during the decay of organic matter it aids and promotes the production of nitric acid by the process of nitrification. Caustic lime, when it is reconverted into carbonate, has no chemical virtue over mild lime, but it has the mechanical advantage of being in a fine powder and more uniformly diffused through the soil. The mechanical action of lime is, that it (1) adds bulk to the soil, and (2) makes it looser and more friable by keeping the clay coagulated, and it assists (3) the percolation of water through stiff soils. 451. A form of lime not considered very valuable as a manure is gas-lime, and as such it is principally used in the heavy clay districts. The principal use of gas-lime is as a specific for wire- worms, and fresh gas-lime at the rate of ten or twelve tons per acre is a pretty certain cure for these pests. Fresh gas- lime contains sulphides and sulphates of lime (combinations of quicklime and sulphuretted hydrogen), which are in- jurious to all forms of life, whether fungoid, vegetable, insectal, or animal. So when it is proposed to use gas-li«ie to destroy anything, it should be used as fresh as possible. But when used for manurial purposes, gas-lime should be 272 PRINCIPLES OF AGRICULTURE. exposed to the air until these sulphides and sulphates are converted into gypsum (sulphate of lime). This may he done by carting the gas-lime into heaps, and allowing it to remain for twelve months before use, or the process may be hastened by mixing the gas-lime with an equal bulk (or a greater bulk) of any refuse materials. And similarly the same end may be secured by spreading the gas-lime on the surface of the land, and allowing it to remain there. Gas-lime and lime of all kinds is removed from the soil by several causes. The rains wash it out from the land, the crops carry away a portion of it, and it has a great natural tendency to sink into the land out of the reach of plants. In wet and undrained soils this sinking tendency leads to the formation of a pan. 452. From what has been said in this chapter, it will be seen that lime may be used as a manure when it is in either of the following forms: (1) Quicklime or caustic lime; (2) gas-lime — i.e. lime which has been used in gas- works in the purification of the coal-gas ; (3) slaked lime — i.e. quicklime which has combined with water, and is therefore a hydrate of lime ; (4) carbonate of lime (usually applied in the form of chalk) ; (5) gypsum or sulphate of lime ; (6) phosphate of lime. Questions. — 1. What are the effects on a soil of dressing it with carbonate of lime and quicklime? 2. Why is quicklime said to be an exhauster to the soil ? What are the conditions you would lay down for regulating the use of quicklime ? 3. In what forms do we use lime as a manure, and what are the special advantages of each ? 4. Hoav does the character of the soil influence the use and application of lime ? 273 THE CROPS OF THE FAEM. [7. Crops. — Show amounts of dry matter, nitrogen, phosphoric acid, potash, lime, and silica in average crops of wheat, barley, oats, meadow Jiay, red-clover hay, beans, turnips, mangel and potatoes, and any other crops coinmon to the district, in pounds per acre — Classify as rich or poor in nitrogen, in potash, in silica — Regard separately the part of the crop removed from the field, or sold off the farm, p)ointing out what procedure exhausts the land most in important ash constituents — Show, if possible, icliat is the loss to the land by sale of products in any simple rotation usual in the district. Point Old the suitability of different crop)S for various climates, and any marked preference of particular crops for a special hind of soil — Show the differences in the root develojmient of crops, their length of p>eriod of growth, the feeding power of their roots — What is easy for one crop to obtain is difficult for another — Compare wheat and beans as to their capacity for obtaining nitrogen and silica, and turnips and mangel as to their capacity for obtaining phosphates from the soil — The selection of manures is generally based on the special needs of the crop, and not on its composition ; a general manure frequently not required^ Shoiv from public ex- periments the effect of nitrcde of soda on cereal crops and mangel, and the effect of superpthosphate on barley and turnips — Some cro2)s, as potatoes and pasture, visually require a general mamire.'] CHAPTER LIY. ROTATION OF CROPS. 453. The expression ' rotation of crops ' means the order in which a series of crops is made to follow each other again and again on the same ground. Rotations are to he found in many systems of farming. These systems may be classed as follows : R 274 PRINCIPI^ES OF AGRICULTURE. (1) Continuous crop growing, or growing the same kind of crop year after year on the same land without manure. This is TuU's system, and the system in new countries on virgin land. (2) Bare fallowing, that is, giving the soil a rest from crop growing. (3) Lois Weedon system of alternate crop and fallow. (4) Green-crop fallowing, where a green or root crop is substituted for the bare fallow. (5) All grass and stock and no crop, as on hill-farms. (6) Front's 'profitable clay farming,' as carried on at Blount's Farm, Sawbridge worth, where no farmyard dung was either made or applied, and no live-stock kept except ten working-horses. The whole of the crop, hay, and cereals were sold off the land, and the manures used were artificials, which presented plant essentials in a fairly soluble form. (7) Growing crop under a system of irrigation. Adaptations, modifications, and combinations of these systems are what will be found in modern practice. 454. Three great objects are attained by growing crops in a good rotation : First, a larger amount of food is obtained, with less exhaustion to the land, and at a smaller expense, than can be obtained by any other means ; secondly, provision is made for a thorough cultivation and cleaning of the land ; and, tlnrdhj, the rotation is a great convenience to the farmer, and lessens his risks. 455. By this time we are quite familiar with the fact that some crops draw very largely on the soil for certain ash constituents, while other crops take very little of these particular substances, but require more of other ash con- stituents. The cereals, for instance, take a very large quantity of silica and very little lime ; while the legumes and roots take a very large quantity of lime, scarcely any silica, and a very much larger quantity of potash, than the ROTATION OF CROPS. 275 cereals; so that, by growing cereals alternately with the legumes and roots, the demand for the different ash con- stituents is more evenly divided amongst them. And thus a crop of beans and wheat can be grown with less exhaus- tion to the land than either two crops of wheat or two crops of beans in succession ; and at the same time, the total yield of the two unlike crops will be greater than that of the two like ones. Too much stress must not be laid on the silica taken by plants, as it seems in part an accidental ingredient; and Pierre has shown that it is erroneous to attribute the ' laying ' of corn to a deficiency of silica. 456. Another fact is, that some crops are subsoil feeders, and others surface feeders; some what we may term choice feeders, others greedy feeders. We can see that if two deep greedy feeders are grown in succession they will exhaust the subsoil more than a greedy and a choice one, and that two greedy surface feeders will in like manner impoverish the surface soil more than a greedy and a choice one. Now, if the greedy ones are mainly spent on the land where they are grown, their hungry searching nature actually enables them to collect food for choice ones that will feed in the same ground. For instance, clover goes very deep, and collects and feeds on nitrogen in almost any soluble form, and in its abund- ance of roots stores up a supply in the subsoil for the deep-rooted wheat which may follow. Or, again, the hungry surface-feeding turnips are fed off by sheep, and so the surface soil is well filled with plant-food in a good form for the choice surface-feeding barley which will follow. 457. But besides these diflferences of foods, differences of feeding grounds, and differences of feeding powers, crops differ in the times of their growth. Turnips grow all through the summer and autumn, and not only seize upon the nitric acid that is formed in tHe soil by the decay of 276 PRINCIPLES OF AGRICULTURE. manure and organic matter during the summer months, but prevent the rains of autumn washing the nitrates down beyond the reach of plants, and also secure the ammonia and nitric acid that are carried in from the atmosphere by those rains. Clover, again, by continuous growth through at least two summers and a winter, also prevents waste of nitric acid and other soluble plant-food in the soil. Barley and many other crops, on the other hand, do not commence their active growth till spring ; and nearly cease to draw food from the soil by their blooming time ; consequently they derive no benefit from the nitrates produced in the soil during the months of summer heat ; and if they alone were grown, the nitrates and other soluble substances in the soil, together with the ammonia and nitric acid carried in by the rain, would be in a great measure washed out by the rain each autumn and winter. AVhat a saving of valuable plant-food it must be, then, to let such short-lived spring and early summer feeders be preceded and followed by autumn-growing crops ! 458. From these remarks, it will be seen that the first advantage stated as arising from a good rotation is one of very great importance to the farmer. But it is not left for man to settle this question alone, for nature herself teaches the necessity as well as the advantage of growing crops in rotation, in many cases. For instance, an attempt to grow clover or beans continuously on the same land results in clover or bean * sickness ; ' and the continuous growth of turnips results in poor or diseased crops. 459. In the second place, a good rotation provides for the thorough cultivation and cleaning of the land. In some of our early chapters on tillage, we showed the im- portance of tillage operations, both as a means of enriching the land and ridding it of weeds. And in a good rotation, the land, during one year of the course, is set apart specially for this purpose, and only such crops are then grower on it KOTATION OP CROPS. 277 as will not interfere with its "being tlioronghly stirred and cleaned. The land tlms set apart for cultivation and clean- ing is termed fallow land. 460. The objects of fallowing are : (1) To clean the land, and (2) to give it a rest from grain-crop growing. By it (3) the soil gets weathered ; and (4) when a fine surface is kept, nitrogen is absorbed from the air; (5) a fallow crop produces green winter food, and thus provides an extra amount of manure. The great disadvantages of bare fallowing are : (1) The want of a crop, with consequent growth of weeds. (2) The loss of plant-food (nitrates) in wet seasons, by washing by rain. (3) The cost of the system, the land not giving any return while bare of crop. 461. The third advantage of a good rotation is its general convenience to the farmer. By having his farm divided into as many parts as there are courses in the rotation, his prospects are not all staked on one crop : if his corn be spoiled with rain, his cattle-food may be abundant; and the same rain that spoils his hay greatly favours the early growth of his turnips. Again, by cultivat- ing a variety of crops that require attention at different times of the year, the labour of the farm is more uniformly spread over every part of the year. In early spring, in the United Kingdom, ploughing and harrowing have to be done for spring-sown corn ; later, the farmer is busy, well stirring and cleaning his fallow, and sowing his earlier roots. In early summer, sheep-shearing, turnip-sowing, and hay- making Avill keep all hands employed; and turnip-hoeing and harvest work of various kinds will follow close after each other till early autumn. Autumn cultivation for wheat, and the storing of roots and orchard fruits, will next have to be done ; and in winter, hedging and ditching, threshing, and extra cattle-tending will still find 278 PRINCIPLES OP AGRICULTURE. occupation for many; This variety also tends to spread expenses over the \vllole year, and to give the farmer com- modities for market at hearly all times. 462. ' Rotation of ctops,' then, is the order in which farm-crops are groWn^ in relation to each other on the same land, through a setles of years ; the principle being, to grow on the same lahd the same species of crop, only after the greatest interval of time that is consistent with good management and remunerative return. On this subject there are two general rules : (1) Crops that require the same ingredients for their growth should be as far as possible from each other in any rotation. (2) Crops with roots of the same habit of growth should not follow each other. Clover, which usually precedes and is a good preparation for wheat, is considered by some farmers an exception to this rule. Questions. — 1. What are the ol>jects of fallowing, and the disadvantages of a bare fallowing? 2. Give two rules regarding rotation of crops. 3. Name some systems of farming. CHAPTER LV. ROTATION FOR A LIGHT SOIL. 463. We will first take a rotation suitable for light soils. The crops that are best adapted for such soils are turnips, barley, and clovers; Though wheat is best grown upon naturally firm soils, yet the cultivation of clover will enable even light soils to produce fair crops of wheat. 464. The rotation about to be mentioned is one in very general use in England, especially in the east, centre, and south ; but is often slightly altered from its simplest form to suit the special character of the soil. It is called the ROTATION FOR A LIGHT SOIL. 279 Norfolk rotation, and is a four-course rotation, which nieans that it consists of a series of four crops, each of which comes round on the same laud in proper order every four years. 465. Light soils are cheap to work, as they can easily be broken up by the plough with a small expenditure of horse-power, and can be reduced to a line condition and thoroughly cleaned without much trouble. They are also much improved by sheep-treading and sheep-manuring ; and the crops are very suitable for sheep feeding on the land in folds. We must therefore always associate in our minds, light soils and the IS'orfolk or four-course rotation. But these same soils are unable to retain moisture and soluble plant-food Avell, and are therefore generally poor, and unable to stand drought. 466. The following diagram is intended to represent the four divisions of a farm cultivated on the four-course system. The rotation moves from right to left, so that No. 1 field, which is in cropped fallow now, with turnips, will bear barley next year, clover the following, and lastly wheat; after which it will come in as fallow again. FOUR-COURSE OR NORFOLK ROTATION. Field No. 1. Field No. 2. Field No. 3. Field No. 4. 1st Year Cropped Fallow, Turnips, and Swedes. Barley. Clover. Wheat. 2d Year Barley. Clover. Wheat. Fallow. 3d Year Clover. Wheat. Fallow. Barley. 4 th Year Wheat. Fallow. Barley. Clover. 280 PRINCIPLES OF AGRICULTURE. 467. The first thing noticeable about this rotation is, tliat half the farm is producing corn for market ; and half, fodder for sheep. Also that the fodder crops are grown alternately with the corn crops ; and that the first fodder and corn crops are surface feeders, and the second, subsoil feeders. Further, that the land undergoes a thorough tillage and cleaning every fourth year. By the frequent growth of fodder crops, and thorough tillage, the fertility of the land is kept up. This typical rotation may be represented also in this manner : FalloAV Crop. Cereal Crop. <^ / Cereal Crop. Leguminous Crop. In this rotation many plants may be grown : (1) An autumn-sown cereal. — Wheat. (2) Fallow Crop. — Eoots : Turnips, mangel, cabbage, potatoes, &c. (3) Spring-sown cereals. — Barley or oats. (4) Leguminous crop. — Clover (hay), peas, beans. 468. We will follow the rotation through. First of all, the old wheat stubble is broken up by the plough, and the land receives a good manuring with farmyard manure, and perhaps a little phosphate of lime in a very slowly soluble form. The farmyard manure should be well rotted, so that it may not take up much room in the soil, and should be applied just before sowing-time, because light soils are not retentive enough to hold the soluble matters of the manure for any great length of time before the crop is able to make use of them. By means of roller and harrow a fine tilth is ROTATION FOR A LIGHT SOIL. 281 obtained, the weeds are collected and burned, and the fallow is ready in England for swede-sowing in May^ and turnip- sowing in June. All through the summer the soil is kept hoed between the rows, and thus the dormant food in the soil is gradually made soluble by the action of the rain and air, and the roots greedily feed upon the active plant-food thus produced, as well as npon the manure which was applied, and the nitrogen carried into the soil in autumn by the rain. And by cropping the fallow with roots, the active plant-food produced in the soil by fallowing is prevented from escaping from the soil. 469. In winter the sheep will consume these roots on the land, and so the plant-food that has been collected by the turnips from the various sources we have just mentioned will be again added to the surface soil in a slowly soluble form for the barley crop of the following year. Clover will be sown in the young barley in spring, and though at first it may take some little surface-food from the barley, its roots will soon go beyond the roots of the barley, and feed in a lower layer of the soil. After the barley has been harvested, the clover should have a top-dressing of well-rotted farmyard manure, to give it a good start for the winter. Its roots will continue to spread and search for food all the next spring and summer, and so prevent any loss of plant-food by drainage ; and after the farmer has removed the first crop of clover as hay, and penned his sheep on the aftermath, he will plough the clover stubble up in autumn for wheat. The wheat will find a supply of food at the surface, in its first stage of growth, from the sheep manure and decaying clover stubble and leaves, and in the subsoil, in its later stages, from the decay of the clover roots. 470. This rotation may be lengthened into a five or even six course, by keeping the clover down for one or two more years before ploughing it up for wheat; it would 282 flUNCIPLES OF AGRICULTURE. then be : Roots, Barley, Clover, Clover, Wheat ; or, Roots, Barley, Clover, Clover, Clover, Wheat. What is here called clover, would then probably be a mixture of sainfoin, white clover, perennial (not common) red clover, and trefoil, as these succeed better for a few years together than common red clover, along with grass seeds. The five-course or Berwick rotation is : Wheat, Roots, Barley, Seeds (hay), Seeds (pasture). In Scotland oats follow clover, and the usual rotation for a light soil is : Roots, Wheat or barley. Clover and seeds (hay), Clover and seeds (pasture), Oats. Questions. — 1. What do you understand by the Norfolk rotation, and how may it be most easily converted into a five, six, or seven years' rotation? 2. Briefly explain why it is ad- visable to adopt rotation of crops. 3. What is meant by a good rotation of crops, and what advantages does the farmer gain by it ? CHAPTEE LVI. ROTATION FOR A CLAY SOIL. 471. We have said that clay soils are retentive of moisture and manure, and they are therefore either natur- ally more fertile than light soils, or are more capable of becoming so by liberal manuring, and are better able to stand a drought. But they require to be well drained, and cultivated on a system that will tend to separate the particles of soil, and make the land more friable in texture. Clay soils are very expensive to work, for they require a great expenditure of horse-power to break them up ; and it is very difficult to clean them, and reduce them to a fine condition. Autumn cultivation by steam-power for the next summer's fallow, by which the soil is exposed in a rough condition to the crumbling influence of frost, has consequently been found of great benefit to these soils, •where the climate is not too wet. As roots cannot be ROTATION FOR A CLAY SOtL. 283 eaten on tlie land, they have to be carted off, and the manure carted back again ; this is a further expense that h'ght lands are not subject to. 472. The crops suitable for clay soils are, wheat, beans, oats, mangels, kohl-rabi, cabbage, clovers, and those forage crops that can be eaten off in summer, such as vetches, early white turnips, rape, and trifolium (crimson clover). Clay farms generally have a large 2:)roportion of the land laid down in permanent pasture, and therefore must be made suitable for cattle-feeding. Hence clay farms are always associated in our mind with wheat-growing, and dairies or cattle-feeding. 473. The following is a good rotation for clay farms : Fallow Crop (vetches, cabbages, mangel, rape, &c.). Wheat, Clover, Wheat, Beans. It will be seen that this is a five-course rotation, and that wheat comes after the fallow, when the land is in its most fertile condition ; it thus takes the place of the barley of a light soil. It will also be observed that the rule of alternating the cereal with leguminous or fodder crops is unbroken. But by this system of cropping, beans are grown for market, in addition to the two wheat crops. On poor cold clays, oats frequently take the place of the second wheat crop. 474. The cleaning only takes place once in five years, consequently some of the land becomes very foul, and requires the whole of the summer to clean it thoroughly ; when this is the case, only the cleaner portion of the fallow can be cropped. On rich clays this rotation is often lengthened into a six-course, by growing another crop of wheat after beans thus : Fallow (bare or cropped), Wheat, Clover, Wheat, Beans, Wheat. By this course, a farmer would have two-thirds of his farm producing corn for sale each year. Another modification of the six-course shift is Roots, Barley, Clover, Wheat, Beans or potatoes. Wheat. In Scotland the oat crop adapts itself better 284 PRINCIPLES OF AGRICULTURE. to the colder climate than wheat. The most successful rotation is the following, practised in East Lothian : Turnips and swedes, Barley, Clover (seeds), Oats, Potatoes, Wheat. In the Carse of Gowrie, a rich clay district, the East Lotliiaii course is altered to a seven-years' course : Fallow (bare or cropped), Wheat, Barley, Clover, Oats, Beans, Wheat. 475. We will note the way in which the fallow would be cropped in the southern half of England. The cleanest portion of it would be ploughed up in autumn, as soon as the previous corn crop was removed, and winter vetches would be sown. These would be eaten off, or cut as green fodder for horses and cattle late in spring, in time for the ground to get a thorough summer's cleaning. The next cleanest j)ortion might be cleaned, and well manured for cabbage-planting in spring, and kept well hoed between the rows, as long as the size of the plants allowed of its being done convoiiently. A considerable portion of the fallow would be well cleaned and manured for mangels. Kohl-rabi might also be planted, if the farm were situated in a mild climate ; or early white turnips, if in a damp one. On fouler portions that took longer to clean, or even on the ground cleaned after tlie vetches, rape might be sown. And the foulest piece of all would probably have to remain a bare fallow. The fallow year is the one for thorough cleaning, thorough tillage, and thorough manuring. 476. Shorter rotations than have been named are known, and used to be practised on clay soils, and still exist. There is the two-course shift : Wheat, Beans ; but as an occasional fallow is taken, it is not exclusively a two-course system. The three-field course is a system as old as the 11th century, and is the system of cropping still practised in Europe among peasant proprietors : Fallow (bare), winter Corn (wheat), summer Corn (beans or oats). The three-course rotation is adapted for poorer classes of clay soil. It is an inexpensive course, and two-thirds is under EOTATION FOR A CLAY SOIL. 285 corn every year. Roots wliicli are expensive to cultivate are not grown, and a large head of stock is not carried. Questions. — 1. Write out a rotation for a clay soil, and show the suitability of the arrangement. 2. Give an example of a ijve-course rotation, and explain why the crops are arranged in the particular order which you show. 3. Point out the essential difference between the cultivation of light and heavy soils. Show how it determines the cropping of the fallow. CHAPTER LVII. ROTATION FOR LOAMS. 477. Loams are the most valuable of all soils, because they are more retentive of moisture and manure than light soils, and are not so expensive to work as clays. Also because almost all crops can be grown on them, and they are adapted alike for sheep-farming, dairy-farming, and cattle-feeding. 478. The following, a modification of the simjDle four- course rotation, is an excellent one for such soils ; and farm- ing of the most profitable kind is carried on under it in Berk- shire and South Oxfordshire : Fallow, Barley (with clover sown in half the barley ground). Beans and clover. Wheat. 479. A piece of the cleanest wheat-stubble is sown with trifolium, which comes in as early green food in spring. Another piece is ploughed and prepared for winter vetches, which will be ready for use as soon as the trifolium is finished. If it be a clay loam, cabbages may be next planted on another patch of the fallow ; or if in the less rainy parts of England, mangels. A considerable portion will be prepared for swedes ; and the trifolium and vetch ground, or any other late-cleaned part of the fallow, will be sown in June with late turnips. 480. From this it will be seen that two crops — fodder and tnrnips — aye obtained in one year off the same patch 286 PRINCIPLES OF AGRICULTURE. of the fallow. Turnips are liable to a disease called 'finger and toe,' if they are grown on the same ground too frequently ; it would be well, therefore, to let them exchange places with mangels when the rotation next comes round. 481. Only half the young barley, which follows the fallow, is sown with clover for the next year ; the other half being required for beans. When the rotation comes round again, the clover and beans will exchange places, and so they only come on the same ground once in eight years. There is no fear of clover or bean sickness under such a system. The beans will be hoed well when young ; and the wheat that comes on the clover portion, will, if possible, be hoed also. By thus taking every opportunity of ridding his land of weeds, and having the fallow every fourth year, the farmer is able to grow a much larger quantity of sheep-keep on his fallow than he would if he allowed it to get into a foul condition. Frequently, too, stubble-turnips or rape are drilled between the beans to furnish sheep-food after the beans are removed. Mustard also, as a 'catch crop,' is not unfrequently grown on the ground of the first corn crop that is carried. 482. This rotation under good management enables a farmer to grow a larger quantity of corn each year than the four-course system in its simplest form; and at the same time to grow a large quantity of wool and mutton. If none of the fodder crops fail, he has a continuous supply of sheep-keep throughout the year, without the aid of pasture- land. The first fodder crop of the year would be the trifolium ; after which would come the vetches; the next crop would be the aftermath clover; and this would be followed by the mustard, rape, or stubble-turnips ; and the stored mangels and swedes, the turnips in the field, and the hay from the first clover crop, would form a plentiful winter supply till trifolium was ready again in the spring. Still, a little pasture is always particularly useful in case ROTATION FOR LOAMS. 287 of failure of any of these crops, or in the event of one crop being finished before the next is quite ready. 483. A considerable quantity of oilcake is frequently used in fattening sheep, which yields a manure rich in nitrogen. So that all that is necessary by this rotation to thoroughly keep up the fertility of the soil, is the purchase of a moderate quantity of phosphate of lime for root-crops. 484. In drawing up any course of rotations some points have to be considered: (1) The suitability of the climate for the plants intended to be grown. The rainfall may be little or excessive. Deeply-rooted crops, as wheat, red clover, lucerne, sainfoin, and mangels, are best fitted to resist drought, while shallow-rooted crops, as grass and turnips, suffer from it. Again, seasons of deficient light and heat mean late harvests. Then the character of the winter has a considerable influence on the followino; season. In climates where the Avinter is wet, nitrates are lost by drainage, and the land contains an excessive amount of moisture. Where frost and snow is the character of the winter, the nitrates are not lost owing to the frozen con- dition of the soil, and the snow when melted is mostly removed by surface drainage. Crops like different climates. Thus wheat likes hot and dry weather, while oats ripen in a moist atmosphere. Mangels require heat and can resist drought, while turnips like a cool moist climate. (2) The next point is the character of the land, for there is a regular connection between plants and soils. Wafer-cress grows where there is carbonate of lime in the water ; the mare's-tail (Equisetum) is present where soluble silica abounds ; clovers like lime, and leguminous crops, gypsum. Wheat thrives in clay, oats and clover in heavy and compact loams, and harley and turnips in open and free loams. Maize likes an open, free, and even sandy soil; rye, a sandy soil; and rice, a stiff, wet, impervious clay. Bean^ 288 PRINCIPLES OF AGRICULTURE. thrive in stiff, well-drained clays ; peas do best on rather light land ; the cocoa-tree, in sandy soils of the coast ; and cotton, in dry, open alluvial soils (sea islands) and dry and porous uplands (chalk-marls of Alabama), with a hot, dry, and somewhat droughty climate. The tea-plant grows in warm sloping banks, on light, dry loams free from clay; the cactus tribe (fleshy and Avater-bearing) in light, dry sands, exposed three-fourths of the year to a burning sun; and oil-palms, in the moist sea-sands of AYest Africa. The cinnamon-tree rejoices in an almost pure sand ; and the hop, in an open, rich, calcareous loam. The date loves sandy but well- watered places ; and coffee flourishes in rich, dry soils and warm situations. Then, again, plants seem to alternate with each other on the same soil. Burn down a forest of pines in Sweden, and one of birch takes its place for a while. 'Jlie pines after a time again spring up, and ultimately supersede the birch. These changes take place naturally. On the shores of the Khine are seen ancient forests of oak from two to four centuries old, gradually giving place at present to a natural growtli of beech, and others where the pine is succeeding to both. In the Palatinate, the ancient oak- woods are followed by natural pines ; and in the Jura, the Tyrol, and Bohemia, the pine alternates with the beech.* 485. The third consideration is (3) the vital power and healthy growth of the plant to be cultivated. Grow a crop too often, and the land gets ' sick ' of it — clover, for example, requires not less than four years of an interval. This sickening occurs in nature ; forests of any special variety, after some generations, sicken and die out. Scotch investigators have pointed out that this is due to the soil becoming sterile of the micro-organisms which give the * The above on the * alternation of plants,' and soils favourable for their growth, is taken from the new edition of Johnston's Elements of Agric ultural Chemistrt/, ROTATION FOR LOAMS. 289 plant its means of life existence. It also indicates a change in the chemical composition of the soil. (4) The next point is the mechanical force or labour of the farm, with its economical application, so that tillage, sowing, and harvesting can be easily and economically done. Late sown and early sown, summer corn and winter corn, and so on, allowing the work itself to be done in a sys- tematic rotation. (5) The last point is the markets or means of sale for the produce when grown. This is a very important and practical consideration. Rotations have sprung from neces- sity, and are kept up by convenience. No system of rotations is to be followed slavishly, but any course can be drawn up which has a principle in it, and which leads to the profitable cultivation of the soil. A farmer may work on the principle of alternating crops — food for man, then food for beast ; a corn crop and a root crop ; a crop sold off the land, and a crop eaten on it; and he can make it as long as he likes, and the more he varies the crop the better. The following table shows the different rotations, and notes some of their modifications and extensions : TABLE OF ROTATIONS. Tivo-conrse Shift.— Vs'hetit, Beans. Three-course Shift. — Fallow (bare or cabbages grown), Wheat, Beans or Oats. Foiir-course Shift. — Roots, Barley, Clover, Wheat. Five-course Shift. — Wheat, Roots, Barley, Seeds, Seeds. Six-course Shift.— liooia, Barley, Clover, Oats, Potatoes, Wheat. Modifications and Extensions of above Courses. — Roots, Barley, Peas, Wheat : Barley, half Beans and Clover, half Barley and Wheat, Roots : Roots, Barley or Wheat, Clovei-, Potatoes, Wlieat: Roots, Barley, Clover, Wheat, Beans or Oats: Potatoes, Wheat, Barley, Turnips, Barley-seeds : Fallow, Wheat, Clover, Wheat, Beans, AVheat : Roots, W^heat, Seeds, Seeds, Seeds, Seeds or Oats : winter Rye and Roots, Wheat, Clover, Clover, S 290 PRINCIPLES OF AGRICULTURE. Oats, winter Vetches and late Roots, early Roots, "Wheat, Barley : Vetches and late Turnips, "Wheat, Barley, ^Yinter Rye and Swedes, Barley, Clover, Wheat. Fallow is the basis of all rotations, and crops grown in rotation are : (1) Fallotc crops, those which are restorative and renovating, taking the place of a bare fallow ; Fodder or green crojjs, those cultivated for green leaf, and have partly the effect of fallow crops ; (3) Cor7i ci'o^js, which are either M'hite cereal or straw crops, and black or pulse crops. 486. CHARACTERISTIC ASH INGREDIENTS OF CROPS. Crops. 1 K2O. 03 Na^O. S MgO. 13 CaO. P.2O5. u SO3. 1" SiO^. .S CI. Wheat grain Wheat straw and chaff 31-3 115 3-2 1-6 12-3 2-5 3-2 5-8 461 5-3 2-5 1-9 69:1 i'l Rye "Tain 28-8 15-4 4-3 2-6 11-6 2-9 3-9 7-9 45-6 5-3 1-9 2-6 588 Rye straw 1-4 Barley grain, with hnsk Barley straw 21-2 21-6 3-5 4-1 8-2 2-4 23 7-7 32-8 4-5 2-0 3-7 28-4 541 Oat grain, with husk. . Oat straw 15-6 20-5 2-5 6-4 7-2 3-8 3-7 7-4 213 4-1 1-5 3-3 46-4 49-5 0-4 3-6 Maize grain Maize stalks 27-8 36-3 3-9 125 15-0 5-7 2-5 10-8 46 8 83 1-5 5-2 1-6 280 Peas 40 9 21-4 31 5-7 7-6 7-2 5-4 38-8 35-3 7 1 4-3 61 0-8 5-4 1-4 6-3 Beans 38-5 32-7 6-0 8-7 7-3 7-3 6-3 25-3 34-6 7-9 8-2 2-2 0-8 5-5 1-5 7-3 Potato tubers. . . 60-9 14-5 1-7 2-7 4-6 16 8 2-4 39 18-3 61 7-0 5-6 1-9 8-0 2-7 4-6 Sugar beetroot Sugar beet tops 480 22-3 10-4 18-8 9-5 16-2 6-4 19-7 14-4 7-6 4-7 65 3-8 3-5 2-3 4-7 Mangels Mangel tops 53 1 29-1. 14-8 210 5-1 9-7 4-6 11-4 9-6 5 1 3-3 7-4 3-3 4-8 6-6 11-3 Turnips Turnip tops 48-6 28-1 8-7 6-0 2-6 2-5 12-1 34-8 10-6 6-7 12-3 133 0-7 1-5 51 8-7 37 17 20-7 19-8 5-2 5-0 10-9 32 7 11-2 31 6-9 8-4 2 3-7 4-9 Carrot tops . 10-2 Kohl-rabi. 46-5 144 5-7 4-0 1-9 4 8-5 33-6 13-3 10-4 7-6 120 0-9 10-4 4-7 Kohl-rabi tops 4-0 ROTATION FOR LOAMS. 291 Questions.— 1. Draw up a rotation for a good loam, and state tlie principle which has guided you. 2. What points would you consider in drawing up any rotation ? 3. How would you modify the Norfolk rotation for (1) a rich loam, and (2) a poor sandy soil ? Give reasons. CHAPTEK LVIII. DISTINCTIVE CHARACTERISTICS OF CROPS. 487. The chemistry of crops points out many distinctive features, and the composition of our ordinary crops is as shown in table, par. 74. The table, par. 486, has been compiled from analyses of the various plants named. The root-crops are rich in potash ; the legumes in nitrogen, with a fair amount of potash and lime ; and the cereals in silica, with a good percentage of phosphoric acid. The following table shows concisely the leading ash ingredients in our crops : I KgO caiid NaoO. .3 1 MgO. s CaO. o • P-Ps. i SiO.2. If SO3. 6 CI. Cereals— Grain 30 13-27 44 27-41 CO 37 33 12 3 7 7 3-9 3-16 4 3 7 5 25-39 6-12 10-35 8 46 5 35 8 8-18 3-8 8 2 50-70 1 5 1-4 3 35 2-5 2-5 4 2-6 5-12 6-13 4 1 2 2 6-7 39 5-17 5 Straw Legumes— Seed Straw Root-crops— Roots. .. Tops Grasses— In flower 488. Cereal crops contain less nitrogen than either root or leguminous crops; the amount of phosphoric acid is 292 PEINCIPLES OF AGRICULTURE. about the same as in other crops, but potash and lime are much less; but the characteristic feature is the large amount of silica, although this ingredient is not essential for their growth, as they can do without it. Wheat and rye have deeper roots and a longer growth than barley or oats, and thus have more time and a larger area in which to get food. Barley roots are more on the surface than any of the cereals. The nitrogen in these crops is obtained from nitrates, and, though they contain the least of all the crops, they respond best to nitrogenous manures, and then to a phosphatic manure when mixed with a nitrogenous one. Grasses which are grown for hay or fodder are like cereal crops, but contain more potash and lime, and less phosphoric acid. Their roots are far shorter, and therefore they are less able to collect food. For this reason, though nitrogen- ous manures have the same effect on them as on cereals, they also want supplies of potash, lime, and phosphoric acid. 489. The leguminous crops are either grain crops, as beans and peas, or fodder crops, as clover and lucerne. The large amount of nitrogen they contain is their charac- teristic feature, it being twice as much as that found in cereal crops, while the quantities of potash and lime are also very large. As a rule, the legumes are deep-rooted plants, and we have already seen that these roots have an appendage, in the form of tubercles, by which they can obtain nitrogen. These micro-organisms are another charac- teristic feature of these crops, as their absence means barrenness for the leguminous plant, and may be the cause of clover- or bean-sick land. The legumes respond best to potash manures, then to phosphates, gypsum, and lime. 490. In the root-crops, potash preponderates, and is the characteristic feature ; they also contain a good amount of nitrogen, lime, and phosphoric acid. Turnips especially have also a large amount of sulphur. Turnips, swedes, and potatoes are surface-feeders; mangels, in comparison, have DISTINCTIVE CHARACTERISTICS OF CROPS. 293 deep roots. Turnips can take up nitrogen from the soil, but have little power to take up phosphoric acid ; the result is, that phosphatic manures are found to be the best for them. Potatoes want general manuring, and also give a good return when kainite is used. Mangels are not like turnips — they can draw nitrogen, potash, and phosphoric acid from the soil, and this makes them an exhaustive crop to grow. Phosphatic manures are not so important as in turnips, and nitrate of soda is found to produce a great elfect. 491. These various characteristics of crops show us the reason why, in practice, the selection of manures is based on the special needs of the crop, and not on its composition. Frequently a general manure is not needed, and far less is it necessary to add all the plant-food constituents of a crop, unless the crop is to be raised on absolutely barren sand. The characteristics of different crops which specially fit them to succeed, or prepare for each other, are, diflferences in periods of growth, range of roots, powers of assimilation, and quantity of food required. Difference in period of growth has a marked effect as regards use of soil nitrogen, for those plants which are actively growing and not matur- ing in summer, will be able best to get supplies of nitrogen through the nitrification going on in the soil. Regarding the power of assimilation little is known, except we see that cereals can assimilate silica, and legumes nitrogen, readily. Wheat, rye, mangels, red clover, and lucerne are deep- rooted crops, while white clover, potatoes, turnips, and barley arc shallow-rooted ; and in a rotation, by growing a deep-rooted crop, the subsoil is made to contribute to the fertility of the soil ; and when a shallow-rooted crop is taken, the food accumulated at the surface is used. 492. The growing of crops means a certain amount of plant-food taken out of the soil. Prom table, par. 74, we get the requisite information regarding the loss which soil may suffer. The crop may be removed from the field 594 PRINCIPLES OF AGRICULTURE. but used on the farm as fodder, &c., or it may be sold off the farm altogether. The latter procedure will exhaust the land more than the former, because in the first-stated procedure, the ash ingredients will be returned in the shape of manure, less tlie small proportion that may have been digested. The loss to the land by sale of products in any simple rotation, is shown in the following table, drawn up by Warington. In the table it has been assumed that the whole of the urine and manure is returned without loss to the land, and no account has been taken of the nitrates lost by drainage. ESTIMATED LOSSES PER ACRE DURING A FOUR-COURSE ROTATION BY SALE OF CORN AND MEAT. Average Phos- obtained Disposal of Crop. Nitrogen. Pj^fjf Pol..sh. per acre. lb. lb. lb. 14 tons. Swedes— 14 tons used in feeding 6 '8 4'03 0"51 40 bushels. Barley— 2 bushels used for seed, 38 bushels sold ..32-3 14-35 960 3 tons. Seeds (clover and grass) — 3 tons of hay used in feeding 1 9 6-51 82 30 bushels. Wheat — 2 bushels used for seed, 28 bushels sold 0-8 13-35 9-05 Straw — half -ton used in feed- ing, rest of straw returned in manure 1-2 0-72 009 82-0 38-96 20-07 Deduct amount received in manure through 440 lb. of oats purchased and fed to horses, and 700 lb. of oilcake purchased and used in feeding 36-5 1274 10-70 Total loss in 4 years 45-5 26-22 937 Average loss per year 11-4 6-56 2-,34 Regarding loss of nitrates by diainage, it is calculated in England that the average annual loss of nitrogen (as nitrates) is not less than 7 lb. per acre. On the other hand, it is calculated that the rainfall annually supplies 4 to 5 lb. of nitrogen per acre, and the quantity absorbed from the atmosphere by plant and soil is unknown. DISTINCTIVE CHARACTERISTICS OF CROPS. 295 Questions,— 1. What are the distinctive characteristics of grasses and root-crops? 2. Show how manuring is affected by the various cliaracteristics of crops. 3. Is there any loss of plant- food in a rotation, and how does it arise ? 4. Name the most effective manures for mangels, beans, barley, and turnips, and state your reason. 493. CLASSIFICATIOIS^ OF FARM PLANTS. PHANEROGAMS. CRYPTOGAMS. 1. Flowering plants. 1. Non-flowering plants. 2. Reproduce by means of seed. 2. Reproduce by means of spores. 1 Include Ferns, Mosses, Sea- 1 1 weeds, Lichens, Fungi. Dicotyledons. MON OCOT Y LEDONS. Gymnosperms. Examples — Fir. Larch. Yew. Contain two seed Contain one seed leaves; usually leaf; produces has a tap-root ; many root- net - veined fibres ; parallel leaves. veined leaves. DICOTYLEDONS— Natural Orders. Crucifer^— Swedes (Brassica campestris) ; Turnips (Brassica rapa) ; Rape (Brassica napus) ; Cabbage (Brassica oleracea) ; Thousand-headed Kale (Brassica oleracea) ; Kohl-rabi (Brassica caulorapce) ; Mustard (Sinapis alba). Caryophyllace^— Spurrey (Spergida arvensis). Linages — Flax (Linum usitatissimum). Leguminos^— Peas (Pismn sativum) ; Beans (Fala vulgaris) ; Clovers (Trifol- iinn), various ; Trefoil (Medicago lupulina) ; Lucerne (Medicago sativa) ; Sainfoin (Onobrychis sativa); Vetches or Tares (Vicia sativa); Bird's-foot Trefoil" (Loitts major and corniculatiis) ; Kidney Vetch (Anthyllis vulneraria) ; Melilot (Melilotus vulgaris) ; Lupines (Lupiuus hiteus and angustifolvus) ; Gorse (Ulex Europceus) ; Serradella (Ornitliopus sativus). Umbellifer^— Carrot (Daucus carota) ; Parsnip (Pastinaca sativum). Composite— Yarrow or Milfoil (Achillea millefolium); Chicory or Succory (Cichorium Intybus). SoLANACE^— Potato (Solaiiuvi tuberosum) ; Tobacco (Nicotiana tabacum). Boragine^— Prickly Comfrey (Sy^nphytum asperimum). Chenopodiace^— Mangel-wurzel (Beta vulgaris) ; Sugar Beet (Beta), species. Polygonace^— Buckwheat (Polygonum Fagopyrum). Urticage^— Hop (II%m%d%is lupulus). MONOCOTYLEDONS— Natural Orders. Liliage^— Onion (Allium cepa). Gramine.e— Wheat (Triticum vulgare) ; Rye (Secale cereale) ; Barley (Ilordeum vidgare); Oats (Avena sativa); Maize (Zea mays); Rice (Oryza sativa); Millet (Panicum miliaceum); Sugar-cane (Saccharum officinarum); Sorghum (SorgJmm aaccharatum) ; All grasses. 296 {The following Chapters give some details regarding our Farm- crops, which it is desirable the student of Elementary Agriculture should study {although not noted in the ^Science and Art' Syllabus), as an introduction to a more detailed and ^advanced' course.] CHAPTER LIX. WHEAT AND RYE. 494. We may divide our farm-crops into three classes — namely, grasses, legumes, and roots. AYe have already spoken of these same three divisions as tlie silica, lime, and potash classes. The grasses may again be divided into the cereals or grain-producers — as wheat, barley, and oats; and the fodder grasses — such as meadow- grass and rye-grass. In like manner, the legumes may be divided into those that are grown for their seed — as beans and peas ; and those that are grown for fodder — such as clovers, vetches, lucerne, and sainfoin. The roots include turnips, mangels, potatoes, carrots, and parsnips. There are also other crops — as cabbage, rape, and kohl-rabi, which, though belonging to the turnip tribe by nature and chemical constitution, are grown for their stems and leaves only, like clovers and vetches ; they therefore form a link between the legumes and roots. 495. The first crop we shall speak of is wheat. There are seven ditferent species of wheat, but the best wheats are found in three groups. (1) Triticum sativum, the common wheat of England, America, and India. (2) Triticum tiirgidiim, cone wheats, grown for quantity, not quality. (3) Triticum durum, hard wheat. The land best adapted WHEAT AND RYE. m for the growth of this important crop is a fertile clay, or clay loam. Some wheats are bearded or awned (fig. 108a), Fig. 108. Webbs' Cone Wheat, beanled variety ((t), ami Kinver Giant Wheat (h). and others beardless (fig. 108^). They are again divided into groups, according as the ears are wliite, reddish, or red, and subdivided according to the smooth or downy character 298 PRINCIPLES OF AGRICULTURE. of the chaff; the final division is determined by the colour of the grain, white, red, or yellow. The term ' chested ' wheat means the number of mature grains formed in eacli spikelet. Wheat is also divided into 'hard' and 'soft' classes, the 'hard' being generally grain produced in climates with little moisture, and contains a large per- centage of gluten. 496. Wheat is generally sown in autumn, and it is hardy enough to stand the cold of a severe winter, particularly if protected by a covering of snow. The variety which is sown in spring is seldom so successful in its growth as winter wheat, though the hard wheats of Manitoba are spring sown. Wheat is not easily affected by a drought on firm land ; in fact, it likes a dry summer and hot ripening time. In spring, the young wheat is rolled to make the land firm, as it thrives best in a firm soil. The points in the selection of seed-wheat are that it be true to its sort, perfect in itself, fully matured, and brought from an earlier district. 497. Wheat should be cut soon after the upper portion of the straw turns yellow, which will be about a fortnight before the grain is quite ripe. The grains are then heaviest, and contain the largest proportions of starch and gluten for grinding into flour. If wheat be allowed to stand till it is ' dead ripe,' some of the starch changes to woody fibre, thereby giving the grains a thicker skin. It is then a better protected seed, but less suitable for the miller, for he likes a grain which contains the largest proportion of flour and the least proportion of bran. 498. The best manures for wheat are a mixture of nitro- genous and phosphatic manures. On fertile soils, nitrogen- ous manures alone have a tendency to encourage a luxuri- ant grassy growth, instead of a large yield of grain ; and especially is this the case in a wet season. This is partly controlled by the use of superphosphate with the nitrogen, WHEAT AND RYE. 299 and more completely by the use of salt. Common salt, like the acids, renders soluble many of the mineral substances in the soil, such as the phosj^hates, and by so doing, enables the plant to mature its seeds sooner than it otherwise would. We can apply nitrogenous manures with profit if we bear in mind the different periods in the life of a plant. (1) Germination, the period parallel to the sucking of a young mammal. (2) Active root production, usually in winter, when leaf makes little progress, and temperature of soil is warmer than air. (3) Rapid formation of the up- ward axis and leaf. (4) Inflorescence, impregnation, and fructification. (5) \\; hi I Maturing' or ripening If nitrofjenous \ \\ manures be applied at the third stage, the growth of stem and leaf is excited ; and if applied at the fourth stage, production of fruit or grain is said to be stimulated, but this is doubtful. 499. Rye (Secede cereale) is a plant (fig. 109) which produces a grain very similar to wheat. In England it is sown as an autumn catch crop or * stolen ' crop, the other crops grown for this purpose being vetches, winter barley, winter oats, and crimson clover or trifolium. Rye is the bread corn of the people of northern and mid Europe. When sown in autumn it ripens early ; when spring sown it occupies the ground longer than any other cereal. It is awned like barley, but it has a sea- Webbs' Giant Rye. green colour which prevents it being mis- taken for it, and is the cereal crop of poor light soils, Fig. 109. 300 PRINCIPLES OF AGRICULTURE. Sometimes a mixed crop of wheat and rye is grown, called Maslen or Meslin, and when grown together, the crop is heavier and the seed larger. In agriculture, by ' seed ' we do not mean the true botanical seed, but that which is sown, so that wheat and rye are naked grains, while barley and oats have an extra sheath. The straw of rye has a pith inside Avhicli makes it good litter, but the worst of all the cereals for fodder. I\ye is subject, along with some grasses, to a peculiar fungoid disease called Ergot, and prevalent when the crop is grown on boggy land. The spurs of ergot are large, and prominent on rye, rye- grass, and tall Fescue Grass, and small and numerous in Cock's-foot Grass. The ])resence of ergot makes rye as a food most dangerous for man and beast. Questions. — 1. Name the common crops which ])articnlarly suit («) a heavy land ; {b) light land. 2. What soil conditions are best for the growth of wheat ? 3. How can you distinguish the seeds of the common varieties of oats, rye, and wheat? 4. Describe what takes place in the germination of a wheat-grain. State its internal and external changes. 5. Point out some broad distinctions between the grasses, legumes, and roots. 6. What are the best soils for rye, and what artificial manure would you use ? Give reasons. CHAPTER LX. BARLEY. 500. Light soils containing lime are generally considered the best for barley. • The reason of this is, that these are the soils which produce the best barley for malting. And this is the purpose for which it is mainly grown in Eng- land. Malting barley, too, brings the farmer a higher price than any other kind. But it does not at all follow that other soils will not produce as large a crop, and of as good quality, for other purpose ^ • in fact, a much larger BARLEY. 301 yield of better feeding barley can be grown on fertile clays or clay loams. 501. Common barley [Hordeum vidgare) is four-rowed, and a variety is called Bere or Bigg. There is also a two- rowed barley {Hordeum disticlium) and a six-rowed {Hordeum hexasHclmm). It is a bearded cereal, the awns be- ing long and rough, and the varieties grown by farmers (fig. 110 a and h) belong to the Hordeum disticlium class. The best known of this class is the Chevalier barley, which is the foundation of many of the best samples of malting barley, which should be plump, fair in colour, fine skinned, sweet, and in a good condition. Hordeum hexasticlmm (English winter barley) is grown almost exclu- sively as a fodder crop. When germinating, as in the process of malting, it will be noticed that the plumule goes upwards under the sheath. 502. Barley matures in a much shorter time than wheat, and can therefore be grown very much farther to the north ^^'^- HO. -Carters' Prize Prolific ,- . , . . . , . - Barley (a), and Goldthorije than wheat, in countries which Barley (6). enjoy only short summers. It requires to be sown in spring, at a dry time ; a wet or rather muddy seed-bed is sure to lessen the yield of barley considerably. It is a shallow-rooted crop, and for this reason, and also because it is generally grown on light soils 302 PRINCIPLES OF AGRICULTURE. that do not retain moisture well, it suffers seriously from a drought. Barley should not be cut before it is dead ripe if it be intended for malting ; for if the albuminoids be not fully matured, an objectionable fermentation may after- wards take place in the preparation of malt liquors. The best barley is grown when land is in a depleted condition, rather than in a high condition. The soil most suitable is a light, dry, friable and porous one, resting on a naturally drained subsoil. 503. The best manures for barley, as for all grasses, are those rich in nitrogen and phosphoric acid ; hence nitrate of soda and superphosphate of lime act very beneficially on a barley crop. 504. We must bear in mind the fact that there is no difference between malting and grinding barley. A¥hat commands the attention of the maltster is malting, and the balance left over is grinding barley. Certain conditions are necessary to produce a good sample of barley which will please the maltster. The place in the rotation must be care- fully chosen and the ground selected with care. Further, the soil must be in a good and proper condition, and the seed of good pedigree, changed from year to year. The climate of England — humid and temperate — is beyond comparison the best climate to grow barley suited for malting, but before it comes into the maltster's hands various little details have to be attended to. Period of cutting affects sample ; grain should be hard (cannot be penetrated by the finger-nail), and out of the pink striped stage. Harvesting must also be done carefully, for should it heat in the rick, it will contract a bitter taste and reddish colour. Again, there are two difficulties in threshing ; it must not be dressed too long or too short. When the awns are taken off too short, the germinating power is less ; if too long, the weight is light. Questions. — 1. What do you understand by malting l)ailey ? BARLEY. 303 What are the points in a good sample of bailey ? 2, Name three species of barley. What is here ? 3. W^liat is the best climate, soil condition of land, and manure for growing barley ? CHAPTER LXI. OATS. 505. The oat is one of the hardiest plants that is culti- vated ; it can be successfully grown on poor clays, on peaty soils, and even on marshy and undrained land; it will thrive at a great height above the sea-level ; and will ripen in a damp climate and at a low summer temperature. These are very unfavourable conditions for the growth of either wheat or barley, and therefore they give place to oats when these conditions prevail. The oat delights in a well-drained, fertile clay, and in a pleasant climate, if not too dry, and gives a large yield. 506. But in addition to being a large cropper, it is a most nutritious grain. When separated from the husk, which, unlike the chaff of wheat, is closely attached to the grain, the oat contains a greater proportion of nitrogenous or flesh-forming matter than either wheat or barley ; and as much as a tenth of its non-nitrogenous (fat-forming) matter exists in the valuable form of fat, whereas in wheat and barley it is nearly all in the form of starch. For these reasons oatmeal is one of the most strengthening and fattening vegetable foods that can be eaten, and is particularly w^ell adapted for growing children, and as a diet for somewhat cold climates like the Scotch High- lands. 507. The nitrogenous part of wheat is called gluten, and wheat contains more of this substance than any other grain. And this is why wheaten flour makes the best bread. The gluten gives the peculiar stickiness to 304 PRINCIPLES OF AGRICULTURE. dough which enables it to stretch without breaking, when blown into bubbles l)y the carbonic acid gas produced by the action of the yeast on the starch of the flour. And so, much of the gas is prevented from escaping, and we get bread full of tiny boles, or as it is generally called, light or crumby bread. Barley-meal is much poorer than wheaten flour in gluten, and therefore is not so suitable for bread-making. And the chief albuminoid of oats is more like legumen than gluten, consequently oatmeal is quite unflt for loaf-making, though it is frequently made into tbin cakes. 508. There are many varieties of oats, some white and some black, some early and some late ; some requiring to be sown in autumn, others in spring; some suitable for high-lying districts, others not, because liable to shed their seeds in high winds ; some suitable for peaty and marshy soils, some for poor clays, and others for better soils. Oats do not grow in compact ears like wheat and barley, but hang, two or three seeds together, on a cluster of little branches. In some varieties, these little branches hang all around the flower-stem, at a considerable distance apart ; while in others, these seed-branches hang closely together, and all on one side of the stem. On account of these peculiarities of growth, the oat-grains on the same stem do not all ripen together : the earlier ones, therefore, have to wait for the later ones, so that oats cannot be cut more than a week before they are dead ripe. 509. There are six species of oats, but the two generally grown are Avena sativa, the Common or Bell Oat (fig. Ilia shows the variety known as Webbs' Challenge White Oat), and Aimia orientales, Tartary or Sideway oats, represented by Webbs' Prolific Black Oat (fig. 111^). The colour of white and black oats is due to the sheath, which is the dried flowering glume and pale. Tartarian oats are widely grown, and are the popular ' horse ' oat, though the ' potato ' OATS. 305 oat is the variety used for high-class horses, as in racing stables. A point to notice in the Potato Oat is that it has Fig. 111.— Webbs' Challenge White Oat (a), and Prolific Black Oat (6). Bosom Pickle in Potato Oat (c). a bosom pickle — that is, a small oat-grain enclosed with the larger grain, and lying, so to speak, on its bosom T 306 PRINCIPLES OF AGRICULTURE. (fig. lllc). Furtlierj this oat is the only exception to tlio general rule regarding oats — that mixed seeds give the best results and returns. Oat straw is good fodder, only second to hay. It has also been noted that nitrogenous manures make a more marked improvement on an oat crop than on either wheat or barley. Questions. — 1. Why does the oat generally take the place of wheat in Scotland ? Compare the two grains in regard to their nutritious qualities. 2. Describe the general appearance of two well-marked species of oats. 3. AYliat do you understand by a bosom pickle ? CHAPTEELXII. MEADOW-GRASS AND MEADOW-HAY. 510. Grass-land is either pasture or meadow. That which is always used exclusively as grazing ground is called pasture, and tliat which is occasionally mown for hay is termed meadow. Most farms have some grass-land, but some few have none, while others consist almost entirely of grass-land. The part of a farm that is regularly under the plough, and actively cultivated, is called the arable or tillage portion. There are two very different kinds of land that are used for grazing purposes. First, the hilly dis- tricts, that are too poor to pay for cultivation as arable lands ; these produce short sweet herbage, upon which large numbers of sheep are fed. And next, the fertile plains in damper districts, and the banks of the rivers, where luxuri- ant crops of rich grass fatten our cattle, and supply us with milk and butter and cheese. Dairy-farms prevail in these districts. The drier parts of a country that are better adapted for the perfect ripening of corn, are chiefly laid out in arable farms. In England many of the pastures MEADOW-GRASS AND MEADOW-HAY. 307 have never been anything but pastures for hundreds of years. 511. The first great aim in the management of meadow- land should be to secure a nutritious variety of grasses, and this cannot be attained if the soil be wet and badly drained, or too poor. Some grasses are of little value as food, and are disliked by cattle. A meadow that will not allow water to pass easily downwards, will produce rushes and coarse aquatic grasses of an innutritious and sour char- acter. Good drainage will soon cause these kinds to die out, and more nutritious grasses to spring up ; and a dressing of lime or gypsum (sulphate of lime) will destroy sorrel and sour herbage, and encourage the growth of clovers. Manuring with good farmyard manure will make mosses, daisies, and other plants that are always a sign of poverty, disappear, and cause a luxuriant growth of the better meadow-grasses. When a poor meadow has been well drained and manured, a good start should be given it by sowing seeds of the best grasses, such as the ryegrasses, cock's-foot, fescues, foxtail, smooth and rough meadow- grasses, timothy, dog's-tail, sweet-scented vernal, and peren- nial clovers. 512. The same manures which are beneficial to the cereals are also best for ineadow-gmsses. Phosphatic manures must be applied to supply the place of the phos- phoric acid that is annually removed from pastures, in the bones and milk of the animals fed upon them. And nitrogenous manures may be applied more liberally than to the cereal grasses, because luxuriance of stem and leaf is just what the farmer aims to get in his meadows ; but in the cereals, the luxuriance attained in the straw, by the use of nitrates, is often at the expense of the ear, and there- fore needs control. We have already learned tliat at blooming time the stem and leaves contain the largest amount of soluble nitrogenous and non-nitrogenous sub- 308 PRINCIPLES OF AGRICULTURE. stances; and that later, much of the soluble non-nitro- genous matter changes to the indigestible woody fibre of the stem, while the rest, with the nitrogenous matter, goes up to form the seed. So that if the farmer lets his grass ripen, the seed sheds, and he loses all the flesh-forming substances, and has little else thau indigestible woody fibre left. Grasses seen in new and uncultivated soil indi- cate roughly peculiarities of soil, seasons, and climate. America has its ' blue grass ' country, and Australia its ' kangaroo grass ' country. 513. For hay-making, the farmer likes warm, drying winds rather than a scorching sun ; the grass then loses its moisture thoroughly, without at the same time losing its sweetness and fragrance. If grass gets much rain after it has been partly dried, a good deal of the soluble nitrogenous and non-nitrogenous substances will be washed out, and the hay will be of much less feeding value. Much of these substances will also be lost if the hay be carried before it is sufficiently dried ; the loss will then be due to the escape of gases produced by the fermentation which will take place in the rick. The heat produced by this fermentation is sometimes sufficient to set the rick on fire, and oftencr, to char much of the hay in the centre, and make it useless. 514. Ryegrass, and Italian Ryegrass (frequently mixed with red clover), are often very profitably grown for green fodder on light soils, as arable crops, taking their place in the ordinary rotation. They are very tall grasses, and yield large crops, and are sometimes allowed to remain down for more than a year. If Italian Ryegrass be regularly irrigated — that is, flooded at regular intervals, on well-drained land — it will yield as many as six crops a year. It may live for several years. 515. In the following table, drawn up by Mr James Hunter of Chester, are noted the chief grasses and clovers sown, and known in a rotation as ' seeds : ' MEADOW-GRASS AND MEADOW-HAY. 309 STANDARD OF GERMINATION, AND WEIGHT OF GRASS AND CLOVER SEEDS. cd .^ Number ?.S l^ Number of ger- NAME OF SPECIES. -S5 II of seeds in one pound. minating seeds in s,^ ^ poiuid. Alopecurus irrateiisis (Meadow Foxtail) 85 11). 14 490,000 416,500 An'homnthum odomtum (Sweet Vernal) 70 12 738,000 516,600 Avena ehULor (Tall Oat-like Grass) 85 14 138,000 1.400,000 117,300 980,000 Avena Jlavescens (Golden Oat Grass), 70 10 Cynosurus cristatus (Crested Dog's-tail) 90 34 886,000 797,400 95 21 426,000 578,000 246,000 1,561,000 404 700 Festuca dnriuscula (Hard Fescue) 90 23 520,200 221,400 1,326,8.50 FestiKxi eliUiov (Tall Fescue. 90 25 Festum ovlna tenuifolia (Fine-leaved Fescue) . 85 26 Festuca pvcifcnsis (Meatlow FescueV 98 28 236,000 270,000 223,000 1,320,000 231,280 256,500 218,540 1,293.600 I olium pevenne (Perennial Ryeirrass). 98 28 Phleum pmteme (Cat's-tail or Timothy) 98 50 80 26 2,325,000 1,860,000 1,860,000 1,488,000 Poa pratensis (Smooth-stalked Meadow-grass). 80 30 Pwi trlvkdis (Rough-stalked Meadow-grass). . 96 28 2,235,000 2.145,600 Achillea MUlefolinm (Yarrow or Milfoil) 90 35 3,510,000 3,159,000 Lotns corniculattts (Bird's-foot Trefoil) 90 66 412,000 370,800 Medicago lupidUm (Trefoil or Yellow Clover) . 98 66 319,000 312,620 Medicano sativa (Lucerne).. . . 98 64 224,000 718,000 232,000 219,520 703,640 227,360 Trifolium hyhruliim ( Alsike Clover) 98 66 Trifolium pratense (Red or Broad Clover) 98 65 Trifolium pratense perenm (Perl. Red Clover). 98 65 218,000 213,640 Trifolium repens (White or Dutch Clover) .... 98 66 732,000 717,360 QUESTIONS.— 1. What niaiiuiing is best for pastures? 2. Name some of the grasses sown as ' seeds ' in a rotation. 3. What class of land is generally laid down in grass ? What systems of farming do you find when the area under grass is large ? CHAPTER LXIIL GRASS SEEDS. 516. All the grass seeds sown either in rotation or permanent pastures belong to the Graminese. One-third of the natural grasses and all the cereals are annuals or biennials, which die after seeding. Two-thirds are per- 310 PRINCIPLES OF AGRICULTURE. ennialsj mostly fibrous rooted, and live on after seeding from year to year. The five main grasses for the farmer are : Meadow Foxtail, Timothy or Cat's-tail, Cock's-foot, Meadow Fescue, and Ryegrass. Some farmers also con- sider the Meadow-grasses or Poas as one of the principal grasses. These we will study very slightly so as to obtain some idea regarding this branch of our farm-crops, without which our elementary knowledge would be incomplete. 517. Meadow Foxtail {Alopecurus pratensis) is a large grass having the three requisites of earliness, good quality, and quantity, and grows best on soils of medium texture and good quality (fig. 112, A). Mr James Hunter, the seedsman, of Chester, who has studied our grass seeds thoroughly, and regarding their adulteration is a recognised expert, says that no grass seed affords greater opportunities for adulteration than Meadow Foxtail. The seeds chiefly used are those of Yorkshire Fog (fig. 112, B), Black Grass (fig. 112, C), and perennial Ryegrass (fig. 112, D). Rye- grass seeds are mixed with Foxtail to bring up weight, as one Ryegrass seed equals in weight three well-matured Foxtail seeds, besides the fact that Foxtail seeds are five times the commercial value of Ryegrass. The points of difference between Foxtail and Yorkshire Fog are these: The husk or outer covering of the seed of the Meadow Foxtail is furnished with an awn or hair nearly as long as the husk itself, and the edges of the husk are thickly set with fine silk-like hairs that arc visible to the naked eye, the seed enclosed in the husk being Jlat, hroivn in colour, and adherlmj to tJie-husJc. The husk of the Yorkshire Fog, however, is rather smaller than the Foxtail, is not furnished with an awn, and although there are short hairs on the edges of the husk of the I/olcus, yet they are only seen with a magnifying lens, and the seed enclosed in the husk is egg-shaped, silvery, shiny, and readily separated from the husk. The points of similarity between Foxtail and Black Fig. 112.— Various Specimens of Hunter's Grass Seeds. 312 PRINCIPLES OP AGRICULTURE. Grass are, tliat both arc terminated l)y an awn nearly the lengtli of the husk, are nearly fiat, or else slightly concave, on the face, and convex on the back. The points of dis- similarity are these : In Foxtail the husk is greenish white, with silk-like hairs at the edges visible to the naked eye, and tlie seeds are very soft and smooth. In Black Grass the husk is light brown, with no hairs visible to the naked eye, and the seeds are hard and rough, and thicker and longer. 518. Timothy, or Cat's-tail (Phlemn prafejise), is a grass highly esteemed in America, and in a way resembles Earley (fig. 112, E). Hay made from it is of excellent quality; but while Foxtail gives a good aftermath, Timothy has very little. It is largely used in rotation grasses, and has been recommended to replace Ryegrass. Many farmers state that Timothy is anything but a good pasture grass, having very few leaves, although it is one of our best hay l)lants. The seeds are little, round, and compact, and of a bright silver-gray colour, and as this does not lend itself to adulteration, pure seed is easily obtained. Samples of American and Canadian Cat's-tail have a larger proi)ortion of the seeds separated from the husk than samples from the Continent, and this gives them a darker appearance. While Foxtail is a poor germinalor and the seed is expensive, Cat's-tail is cheap and very free in germination. 519. Cock's-foot, or Orchard Grass {Dacfylis fjlomeniia), is considered the best of all the permanent grasses, being very succulent and independent of drought (fig. 112, F). It is a coarse-growing grass, growing in a cushion or hassock form, having long hard seeds, and can be grown on heavy or light land. As impurities in Cock's-foot are found .the seeds of Yorkshire Fog (fig. 112, B) and soft Brome-grass (fig. 112, G). Cock's-foot is also adulterated with small seeds of perennial Ryegrass (fig. 112, D), which increase the weight of the sample, and give to the Cock's- GRASS SEEDS. 313 foot an apparently higher percentage of germination than it might otlierwise have. Seeds of the Blue Moor-grass (fig. 112, H) are also used to adulterate Cock's-foot. 520. Meadow Fescue (Festuca pratensis) is another grass of great value as regards quantity of produce and nutritive value (fig. 112, I). The Fescues are an important group of agricultural grasses, and Meadow Fescue is a good example of the broad-leaved form, and Sheep's Fescue of the narrow- leaved form (fig. 112, J). Meadow Fescue grows well on the damper varieties of rich land, and it gives a very heavy aftermath. As the seeds are like perennial Ryegrass, and as the price of Ryegrass is one-fourth that of Meadow Fescue, it is used as an adulterant to such an extent that 90 per cent, of Ryegrass has been found in a professed sample of jMeadow Fescue. If seed be examined by a magnifying lens, Meadow Fescue (I) will be found to have a small stalk Avhich springs from the lower end of the face or front of the seed. This stalk is of one thickness throuu;h- out, is slender, and flanged at the top. Perennial Rye- grass (D) also has a stalk, but it is shorter and broader, wide at the top, and tapers towards the base. It is not flanged at the top, and lies closer to the seed than in the Meadow Fescue. Impurities are also found in the form of seeds of Soft Brome-grass (G) and Rye-seeded Brome-grass (fig. 112, K). Both of these have awns, while Meadow Fescue has no awn. 521. As the fescues are all useful grasses, we will note those in common use. Tall Fescue [Festuca elatior) is very like Meadow Fescue, but larger, every part being nearly double the size. It grows well on heavy and light land, and is found to resist drought well. The seeds resemble those of Meadow Fescue, but are rather larger, longer, more tapering, somewhat rougher on the back, and sometimes terminated by an awn. When adulterated. Rye- grass is used. Meadow Fescue is often sold for Tall Fescue, 314 PRINCIPLES OF AGRICULTURE. and during the past few years the seed of the Xew Zealand Reed Fescue has been sold for Tall Fescuei Hard Fescue {Feduca durimcula) is adapted to a great variety of soils, though produce is small (fig* 112, L). It possesses the quality of withstanding, in an exceptional degree, drought in summer and severe cold in winter, and will grow on lowlands or at a height of 2000 feet above sea- level. It is one of the few cultivated grasses the seeds of Avhich are not often designedly adulterated. Two other fes- cues are known as Sheep's Fescue (Feduca ovina), called in the United States Pine Bunch-grass, and Red Fescue [Festuca rubra), and regarding them Mr Hunter states that under their names the seed of Hard Fescue is invariably supplied ; the larger seeded and rougher samples being used to repre- sent Eed Fescue, and the smaller seeds Sheep Fescue. The illustration (fig. 112, J) is that of fine-leaved Sheep Fescue (Festuca ovina tenuifolia). Here again the common adulterations are the substitution of the smaller seeds of Hard Fescue, and mixing Avith the seeds of Blue Moor- grass. 522. Ryegrass is the next grass we have to study, and perhaps it is the best known of all rotation grasses. Peren- nial Ryegrass {Lolium perenne) grows on all soils and nearly everywhere, and is known under various names, such as Devon Ever, Pacey's Ryegrass, &c. (fig. 112, D). The cheaper samples, if light in weight, will probably not be properly cleaned, and contain seeds of the Brome-grasses, Buttercups, Rib-grass, and other weeds. Italian Ryegrass {Lolium italicum) is much larger than perennial Ryegrass, and surpasses it in nutritive value, earliness, productiveness, and quickness of growth. It is a biennial plant, and thus . not very suitable for permanent pasture. Some authorities consider it is only biennial in ordinary culture, but where well supplied with food it lasts for several years. On a sewage meadow it has been cut from three to four times GRASS SEEDS. 315 each year for five years successively witliout seeding. Italian Ryegrass seed (fig. 113) can be easily detected, so that impurities can be easily seen. Hair-grass and Soft Brome-grass are impurities which have any resemblance to Italian Ryegrass, as they both have long awns ; but Hair-grass seed is dark coloured, very long, and very slender, while the seed of Soft Brome- grass is much broader. In threshing Italian Ryegrass, many of the awns are broken off ; it is then difficult, if not impossible, to say whether the seeds are Italian or perennial Ryegrass. 523. We have now named the main grasses grown 'j but there are a number, of others which are put into mixtures of grass seeds, either for permanent or rotation pasture. The Sweet-scented Vernal Grass {Anthoxanthum odomtum) grows on almost every kind of soil (fig. 112j M). The true Vernal Grass is a perennial, but in place of it a spurious con- tinental species of annual duration is com- monly sold. This annual species is called Fuel's Vernal Grass {Anihoxantliam Puelii), and is shown in illustration (fig. 112, N). Both the Vernal Grasses shown (M and N) have the seed removed from the husk and magnified, and not as in the other seeds illus- trated, shown natural size. True Vernal-grass seed is almost black, while Pud's grass is brown. Fuel's grass is a recognised bad annual weed in Germany, from whence come most of the Vernal-grass seeds of commerce, and this worthless weed seed is gathered and sent to Ham- burg, from Avhence it finds its way into commerce as the true Sweet-scented Vernal. Fig. 113. Hunter's Italian Rye- grass Seed. 316 PRINCIPLES OP AGRICULTURE. 524. Golden Oat-grass {Afcna fiavesceiib) grows naturally in almost every kind of soil, though the produce is small (fig. 112, 0). The seed usually supplied for Golden Oat-grass is that of Wavy Mountain Hair-grass [Aira flexuosa, fig. 112, P), and this is due to the fact that the seed of true Golden Oat-grass is costly, while the other is plentiful and cheap. The seeds of these grasses arc somewhat like each other. To the naked eye the seeds of Golden Oat-grass are light, slender, and of a pale-brown colour, while those of Wavy Mountain Hair-grass are heavier, thicker, and of a darker brown colour. Under the microscope the points of difference are as follow : the Golden Oat-grass has a long bent aAvn which sprhir/s from the shoulder of the seed, near the top or thinnest end. At the base or thickest end short white hairs encircle the seed, mid these hairs are also con- tinued up the front or concave side of the seed. The Wavy Mountain Hair-grass has also a long bent aAvn, but it springs from the base or thick end, and passes up the back of the seed, but does not adhere to it. The lower end of the seed is encircled with long white Jiairs, but there are no hairs on the froid of the seed. 525. Crested Dog's-tail {Cgnosurus cristatus) is a useful grass for high-lying cold pastures, and little susceptible to drought ; but the produce is scanty, and the seed-stems are not eaten by stock, as they are very wiry (Hp. 112, Q). The seed of Dog's-tail has an elegant attenuated form, and bright yellow in colour ; but produce being scanty, it is expensive, and is often extensively adulterated with the seed of Blue Moor-grass (H), which is larger in size, lighter in weight, and darker in colour. 526. The last family of grasses which can be noticed in a brief review of the agricultural grasses (intended only to indicate to elementary readers a scant outline of the sub- ject) are the Meadow-grasses or * Poas.' The most widely distributed member of the group is the GRASS SEEDS. 317 Annual Meadow-grass {Poa annua), but it can only be classed as a weed (fig. 114a). Wood Meadow-grass {Poa nemoralis) grows well in woods and shady places, but pure samples of the seed are costly (fig. 114c). Wood Meadow- grass is adulterated chiefly with the seeds of Tufted Hair- grass or Hassock-grass (Aira caspitosa, fig. 114e), Smooth-stalked Meadow-grass {Poa praiensis) is a grass that has strong creeping roots, can resist drought, and thrives on dry soils (fig. 114/>). It is the famous Kentucky Fig. 114. — Various Grass Seeds (Hunter's). Elue-grass of the United States, and there supplies food all the year round. The seed of it is plentifully produced, so that it is usually obtained genuine. Rough-stalked Meadow- grass {Poa triviaJis) is the best of the ^Meadow-grasses (fig. Il4d). It likes strong, moist soils in sheltered situa- tions, and will not thrive on dry soils. It has a close, quick growth, liked by stock, and as a ' bottom ' grass is unsurpassed. Before 1883, Mr Hunter of Chester states that smooth-stalked Meadow-grass was commonly supplied for it, and that even now this grass is manipulated by machinery to look like rough-stalked IMeadow-grass, and sold in its place, for it usually costs about one-third the price. A careful examination of the seeds of both species in their natural state will show the following characteristics : The seeds of trivialis (rough-stalked Meadow-grass) have a neat, slender, and tapering appearance, have short liairs on the keel or back, and a small tuft of long hairs at the thick 318 PRINCIPLES OF AGRICULTURE. end or base, hut there are no hairs on the edges of the face or front of the seed. The seeds of ^7?*a^e7Zs/6' (smootli-stalked Meadow-grass) have a rougher appearance and are very liairy ; the hairs on the keel or back are long ; the tuft of hairs at the base is larger, and the edges- of the face or front for about half the length of the seed are covered ivith hairs. The most striking difference between the two species is the presence of hairs on the edges of the face of pratensis, and their absence from the same part of the seed of trivialis, and although many of the hairs may have been removed from highly machined samples of -pixdensis prepared to resemble trivialis, some usually remain to attest the identity of ^??-afews/A\ Questions. — 1. What do you understand by grass 'seeds?' Name six important perennial grasses. 2. How would you dis- tinguish between Meadow Fescue and perennial Ryegrass? 3. Name six common agricultural grasses, and the soils they tlnive in. Note also the seeds that are used in adulterating them, if any. CHAPTEK LXIY. BEANS AND PEAS. 527. AVe now come to the second great class of farm plants, the legumes or pod-bearers. They all contain the albuminoid legumen, a nitrogenous substance closely re- sembling the curd or cheesy portion (casein) of milk. They do not as closely resemble each other in appearance as the members of the grass family do, but they are very much alike in chemical composition ; and when their blooms are closely examined, they are all found to be fortued on the type of the pea-blossom, and all contain their seeds in pods, Beans, peas, and clovers, so unlike each other iu BEANS AND PEAS. 319 general appearance, closely resemble eacli other in the par- ticulars we have just mentioned. 528. The leguminous plants take a great deal of lime, and scarcely any silica. They also require more than twice as much potash and nitrogen as the cereals. Being so highly nitrogenous, they are all good flesh-formers, and therefore excellent foods for young or milking animals, and for working stock ; but they require good digestion. We shall first speak about beans — field-beans, often called horse- beans. They may be divided into two kinds — winter beans, which are planted in autumn ; and summer beans, which are planted in early spring. The winter variety is the greater favourite with good farmers, because it generally yields a better crop, though not able to stand the frost of a very severe winter. The bean only thrives on well-drained fertile clays and firm loams, and in a somewhat damp climate ; it is therefore mainly cultivated on the stronger class of land. Beans cannot be grown on the same land continuously as wheat and barley can ; the land becomes what is called hean side. 529. The pea is the only leguminous plant in addition to the bean that is grown for its seed. And the same general conditions that are favourable to the cultivation of the bean also favour a luxuriant growth of the pea. But peas are grown best on what are termed ' barley ' soils. Peas are shallow-rooted, and therefore surface-feeders. They are sown in early spring, and are generally cut before the white grains, thus forming the first-fruits of corn harvest. The straw of well-harvested beans and peas is valuable as fodder ; like all straws, they consist largely of crude fibre which is indigestible, but they are far more nutritious than the cereal straws, and are quite equal to poor hay. 530. The common species of bean is called Faha vulgaris^ and pea, Plsiim sativum. The field-pea is sometimes named Pisum sativum arvense, to distinguish it from the 320 PRINCIPLES OF AGRICULTURE. garden-pea. Kainite and gypsum (sulphate of lime) are suit- able artificial manures for leguminous crops. Farmyard manure, however, is the one more generally applied to beans and other legumes ; . but better results would be obtained if the quantity of it was lessened, and a consider- able addition of kainite and superphosphate given. Questions.— 1. To what class of plants do peas and beans helon<;? 2. What do you understand by a bean-sick soil? 3. What soils and manures are best adapted for the growth of beans and peas ? CHAPTER LXY. LEGUMINOUS FODDER CROPS — VETCHES, CLOVERS, SAINFOIN, AND LUCERNE. 531. The farm- crop that most neaiiy resembles the pea in its habits of growth is the Vetch or Tare ( Vicia sativa). It is cultivated as a fodder crop for horses, cows, and sheep, to be eaten when in bloom. It is mown and carried off the land little by little as required, for horses and cows ; but sheep may be penned on it in small folds. Both winter and spring varieties are cultivated ; and the former is an especially valuable crop, because it comes in as a very abundant and nutritious food-supply at the end of spring, when the winter stores of roots and hay are generally exhausted. The vetch is a particularly suitable crop for clay farms and limy (calcareous) loams. 532. The most valuable leguminous crop, however, that the farmer grows is clover. It not only furnishes him with a large quantity of very nutritious cattle food for both summer and winter use, but improves the soil in a wonder- ful way for the growth of Avhite corn. There are many varieties of clover, but the most important one, and the one most generally cultivated as a distinct crop, is the Common LEGUMINOUS FODDER CROPS. 321 Red Clover {Trifolium pratense). It is one of the deepest rooted of all crops, and flourishes best in a deep, light soil, which contains much lime ; but it can also be profitably cultivated on all except very wet soils. Clover is sown in spring, sometimes among the young wheat ; but generally among the young barley, on farms where barley is grown. After the corn crop is cut, the young clover is top-dressed with manure, and in the following summer, while it is in full bloom, the crop is cut for hay. After the removal of this hay crop, the clover again shoots out, and in about two months is in ])looni a second time, and ready to be cut for another lot of hay. The second crop is called the ' after- math.' 533. Sometimes the clover stubble is allowed to remain for hay another year; but land refuses to produce clover for many years together. Farmers say the land becomes * clover sick,' and this ' sickness ' comes on the sooner if the subsoil is in a bad condition for the roots to search easily for food — undrained, or hard. The property that the legumes possess, of collecting nitrogen and feeding on it, belongs to clover in a marked degree ; its numerous and deeply-searching roots, and its leafy character, greatly help it in this work of finding and using the various compounds of nitrogen which occur in the soil and air. About four times as much nitrogen is contained in the two ordinary clover crops of the one year as would be contained in an ordinary crop of wheat grown on the same land ; and yet there still remains in the roots, stubble, and fallen leaves of the clover, far more nitrogen than can be made use of by the wheat crop which will follow. The growth of clover improves the texture of the land in a way in which no labour could do it. To a light soil, the decay of the roots and stubble adds large quantities of humus, which greatly alters its character and enables it 322 PRINCIPLES OF AGRICULTURE. the better to retain moisture and manure. The clover also feeds upon the plant-food in the soil, and in the manure supplied to it, and retains it in its roots and stubble from being washed out of the soil, as it otherwise would be ; and as the roots slowly decay, the plant-food is set free, and the corn crop gets a regular and continuous supply through the whole i)eriod of its growth. The binding power of the roots of clover also helps to give a firmness to a light soil. Clay soils are also improved in texture by the growth of clover, for the numerous roots, which form a sort of fine network through the soil, help to separate the particles of clay, and so to counteract the tendency which these particles have of sticking together. A clay soil is thus rendered more open and free. The proportion of nitrogenous to non-nitrogenous food in good clover hay is much the same as it is in good wheaten bread ; so that it is as nutritious a food for sheep and cattle as bread is for human beings, 534. There are many other varieties of clover, such as the White or Dutch Clover (Trifolium rejyens), which is short in growth and mainly grown in grazing pastures ; Alsike or Swedish Clover {Trifolium lujhridum), which closely resembles the common clover in growth, but is better adapted for cold, moist, stiff soils ; and Crimson or Italian Clover {Trifolium incarnatum), a very large kind, which, being an annual and shallow rooted, is sown on the unploughed wheat or oat stubble in early autumn, and cut as green fodder early in the following spring. Some other clovers which are sown are Zigzag Clover or Marl-grass {Trifolium medium), Yellow Suckling Clover {Trifolium minus or fiUforme), and Cow-grass {Trifolium j^^'ateiise perenne). A plant called Hop Clover, Trefoil Clover, or Yellow Clover, is not a true clover, as it belongs to a different variety — that is, Afedica(jo lajjidina. LEGUMINOUS FODDER CROPS. 323 535. Tlie only other leginninous crops that shall be described here are sainfom and lucerne. In character and appearance they come between the vetch and clover. Sainfoin (OnohrijcMs sativa) will thrive on poor, dry, chalky soils that nre too poor to be under rotation cultiva- tion, and even yield badly under grass. It is as nutritious as clover either in the green state or as hay, and cattle are very fond of it. In appearance, the leaves resemble those of vetches, but the blossom is more like that of red clover. Sainfoin is much harder than lucerne, and on many lands which give but a miserable return in corn and roots it gives a most remunerative crop. 536. Lucerne, or Alfalfa {Medicago sativa)^ either in the green state or as hay, is the most nutritious fodder that is grown on a farm ; it is even better than clover. Like sainfoin, it produces good crops for about ten years ; its roots strike to such a depth that it does not suffer from drought. In appearance, its blossom resembles that of the vetch, while its leaves are more like those of clover. It thrives best on deep, rich, light soils, but requires some care in the early stage of its growth. Cows are very fond of it, and it is almost the only green fodder except meadow- grass that can be given to dairy cows without imparting an unpleasant flavour to the milk and butter ; this makes it especially valuable. Questions. — 1. Name some common leguminous fodder crops. 2. Name some of the common clovers sown for hay or pasture. 3. What are the advanta^^es of sowin^: either lucerne or sainfoin ? CHAPTER LXVI. OTHER FODDER CROPS. 537. Under this head we place all those crops that do not belong to the leguminous tribe of plants, but whose 324 PRINCIPLES OF AGRICULTURE. stems and leaves, like those of the legumes, are grown for cattle food. Most of them belong to the cabbage and turnip family, and in their chemical composition much more nearly approach the legumes than the grasses. 538. Foremost of these we must place Cattle Cabbage {Brassica oJeracea), because it is a very suitable fallow- crop for clay soils, and probably yields a greater weight of food per acre than any other crop that is grown. This variety of cabbage grows to a great size, especially under the influence of a liberal supply of good farmyard or other nitrogenous manure ; for this reason a dressing of nitrate of soda has been found to have a wonderfully good effect on this crop. Cabbage is capital green food for growing or feeding cattle, and for sheep. It is more largely used for dairy cows than probably any other purpose. The varieties used in agriculture may be classed under two heads — the compact and the open-headed ; of the former the Drumhead Cabbage, and of the latter the Thousand- headed Kale may be taken as typical specimens. 539. Kohl-rabi {Brassica caulorapai) is a plant of the cabbage tribe of very peculiar growth ; the neck of its root swelling out considerably, and forming a valuable article of food for cattle. It therefore more nearly approaches the turnip with its large root than the cabbage with its straight stem, and so forms a sort of connecting link between them. Kohl-rabi is a German word menning cabbage-turnip, and fig. 115 shows that it is a globular cabbage stem, the scars upon it being left by the bases of fallen leaves. It is a suitable crop for clay and peaty soils, and tlu'ives best in a somewhat mild climate. It can be stored for winter use like swedes, and is equal to them in nutritive value ; it is even to be preferred to them as a food for milking-cows, because it does not flavour the milk as unpleasantly as they do. Kohl-rabi is quite free from both insect ravages and mildew, and therefore in OTHER FODDER CROPS. 325 this respect also can claim a superiority to the swede. The varieties cultivated are the green and the purple. Fig. 115. — Sutton's Champion Short-top Kohl-rahi. 540. Eape {Drassica napus) is another plant of the cabbage tribe, with large spreading leaves, in appearance very much like the leaves of the swede ; its stem closely resembles that of the cabbage. It is a deep-rooted cro}>, and like kohlrabi, thrives well on heavy and peaty soils. It is of quick growth, and for this reason is generally grown as a ' stolen ' or ' catch ' crop. A stolen crop is one which a farmer contrives to get between the ordinary crops of the rotation, to supply a pressing want of food for his stock. It is also sometimes grown for the purj^ose of being ploughed in as a green manure. 541. Mustard {Simqn-s alha) is another plant much nscd for ' catch ' cropping and green manuring. It is one of the quickest growing of all crops. Some other plants can only 326 PRINCIPLES oe agriculture. be named here. Furze, Gorse, or Whin (Ulej^ Europceas) is a plant useful in the young state. Buckwheat {Polyyonum Faf/ojJf/ntm) is cultivated as a forage plant, and for green manuring. Chicory {Gicliorium Intyhus) is grown for its root, and is a nutritious forage plant. The Yellow Lupine (Lupinus liiteus) is grown for forage and green manuring. Questions.— 1. What is kohl-rahi ? For what purpose is the plant used ? 2. Name two common forms of cabbage grown for fodder. 3. Name some plants suitable for green manuring and for forage. CHAPTER LXVII. ROOT-CROPS — MANGEL-WURZEL, TURNIP. 542. The last class of crops to which we shall direct our attention is the root class. It includes turnips of various kinds, the mangel-wurzel, potato, carrot, and parsnip. These are all fallow-crops, and are therefore sown sufficiently late to allow of the ground being first thoroughly cleaned and tilled ; and are then drilled in rows, far enough apart to admit of hand and horse hoeing all through the summer, in order that the soil may be hept clean, and as much of its dormant matter as possible made soluble by atmospheric influence. 543. Root-crops are all very great feeders, and grow rapidly; and so furnish the farmer with a great bulk of juicy food for his live-stock; and by thus greedily seizing upon the plant-food. of the soil as fast as it becomes soluble, they prevent the possibility of its being washed through the soil, as it would be in a light soil, on a hare fallow. As an illustration of the feeding power of these crops, we may note that an ordinary turnip crop removes from the soil more nitrogen and phosphoric acid, and much more potash, than a leguminous crop ; and two and a half times ROOT-CROPS — MANGEL-WURZEL, TURNIP. 327 as much nitrogen, one and a half times as much phosphoric acid, and five times as much potash, as a wheat crop. But inasmuch as phosphoric acid is the scarcest plant-food, and tlie one most largely carried away from the farm, in the grain crops, and milk and hones of animals, this is the substance that is found most beneficial as a special artificial manure for root-crops. Copyright ii. & is. Fig. IIG. — Sutton's Maiumoth Long lied Mangel. 544. They all contain a very large percentage of water — turnips, more than 90 per cent. ; this makes them of low value as cattle foods when used alone, particularly in winter, when this water is in a very cold state. But when used with a proper proportion of other dry and nutri- tious food, they impart a moisture and relish to cattle diet, that makes it much more enjoyable and beneficial. 545. The Mangel-wurzel {Beta vulgaris) is one of the most valuable plants of the root class, and in many respects 328 PRINCIPLES OF AGRICULTURE. the most valuable. It is the fodder beet, can be cultivated with great success on clays and clay loams that are not so well fitted for turnips, and being a deep-rooted plant, it is able to thrive well in the drier parts of England — centre and east — and in a dry season. It can also be grown successfully for years together on the same land, whereas turnips cannot. It yields a larger crop than any other Loio life lit to ow ft Fig. 117.— Sutton'fa Yellow Globe Mangel. kind of root, frequently as much as thirty tons per acre. The kinds of mangel-wurzel grown, as shown in figs. 116 and 117, are the ' long ' and the ' globes ' or round, and both kinds have red and yellow varieties. Phosphatic manures greatly improve the soil for the growth of mangels, as they do for all other root-crops ; and nitrate of soda, which does not greatly benefit other root- crops, has a very marked effect on mangels. In places many miles from the sea, a dressing of common salt also noOT-CROPS — MANGEL-WURZEL, TURNIP. 320 improves the mangel crop ; the reason being, that this crop removes from the soil many times more soda and chlorine than any other crop. 546. Mangel seed should be sown in early summer, and tlie aim should be to grow a large number of small roots, rather than a smaller number of such enormous roots as are often now the' boast of the farmer. The mangel, like all the mem- bers of the beetroot family, contains a great deal of sugar; and it is a well- known fact, particularly in France and other coun- tries where beet (fig. 118) is very largely grown for the preparation of sugar, that the small roots con- tain a less proportion of water and a larger .pro- portion of sugar than the larger ones. Much of the sugar in overgrown mangels is changed into indigest- ible woody fibre. Over- manuring is also mischiev- ' Copyright S. & S. ous. This plant will resist ^'S- 118.-Sutton's Blood-red Boet. drought, but cannot stand frost. The plants of this species form also the basis of the sugar industry in France and Germany. 547. Turnips are of many kinds, but it will be sufficient for our purpose to consider them under the three heads of early white turnips, late yellow turnips, and Swedish 330 PRINCIPLES OF AGRICULTURE. turnips (swedes). Early white turnips accomplish tlieir growth in the summer, and can be eaten off by sheep in the dry weather, before the autumn rains fall. Late turnips — yellows — are those most commonly grown ; they continue their growth far into the autumn, and are fed off by sheep, in the United Kingdom, during the winter months. Turnips are surface feeders, and are Fig. 119.— Sutton's Pomeranian AVliite Globe Turnip, consequently unable to stand much dry weather ; hence they are particularly well adapted for cultivation in moist and cloudy climates. They cannot be grown continuously on the same land as mangels can, as they become liable to a disease known as Finger and Toe. This is a fungoid disease, caused, in tlie opinion of ]\Ir Jamieson of Aberdeen, by a too rapid or unnatural growth, severe climatic con- ditions, and acidity of soil and manure. They yield largely, especially after the fallow has been well tilled and manured liOOT-CROPS — MANGEL-WURZEL, TURNIP. 131 with pliosphatic manure. Figs. 119 and 120 show the common forms of turnips that are grown. Fig. 120.- Copj right S & S. -Sutton's Imperial Green Globe Turnip. 548. The distinguishing features of the three kinds of turnip named can be seen in tlie following table : WHITE TURNIPS. Vine or vivid green leaf. Has no neck. Spheroidal. Soft in flesh. Easily injured by frost. White-fleshed. Grows in poor land. Sown late. Consumed first. Inferior nutrient proper- ties. YELLOW TURNIPS. Vivid green leaf. No neck. Spheroidal. Medium in flesh. Fairly hardy. Yellow-fleshed. Medium land. Sown intermediate. Consumed intermediate. Fair nutrient properties. SWEDES. Smooth bluish-green leaf. Has a distinct neck. Cylindrical. Crisp or hard-fleshed. Very hardy. Cream-colour flesh. Good land. Sown first. Consumed last. Highest nutrient proper- ties. Questions. — 1. What are the advantages of growing mangel- wurzel ? 2. State the chief points in white turnips and swedes. 3. For what purpose are root-crops grown ? 33^ ttllNCIPLES OP AGKICULTUREl. CHAPTER L X V I I 1. ROOT-CROPS — SWEDE, POTATO. 549, The Swede {Brassica campestris) is the best root of the turnip family, for it contains a less proportion of water, and a greater proportion of nitrogenous matter, than the Common Turnip [Brassica ixqxi), and although the actual weight of produce is generally a few tons less per acre than of turnips, yet it contains about the same amount of dry matter, and this of a more nutritious kind. In the cultivation of swedes, the farmer must bear in mind one groat rule ; and it is, to secure for the swede plant a long and steady growth. A good, sound grown swede will at once sink when placed in water, while an overgrown one will float like a piece of wood (fig. 121). In order to give swedes a long and steady growth, two- year-old seed should be used ; new seed is more energetic, and often runs up to seed the first year, as if it were trying to produce its seed in one season instead of two. The seed should be drilled early, so that it may have a long growing time before it ; and the superphosphate should bo reduced to a less forcing and more lasting condition by admixture with about half its weight of powdered tricalcic phosphate — bone-meal or ground mineral phosphate — two or three months before being applied to the swede ground. Good swedes store w^ell, and are very suitable crops for loamy soils, even clay loams if Avell drained. 550. The Potato (SoJauum tuherosiim) is in one sense the most valuable root-crop that can be grown on a farm, and in another sense it is the least valuable. As a food, it contains ROOT-CROPS — SWEDE, POTATO. 333 three times tlie amount of nutrition that is contained in the same weight of turnips ; and being in great demand as human food, it realises a far higher price than it would if, like turnips, it were grown as cattle food merely. But, on the other hand, by being sold off the farm, it impoverishes the land of far more potash, nitrogen, and phosphoric acid than a wheat crop ; whereas all other root-crops are eaten by farm-stock, and are therefore to a very great extent Fig. 121.— Sutton's Champion Swede. Copyright S. A; tj returned to the land. Potatoes may be grown on any soil, but are waxy and of bad quality for eating from clay soils, nice and mealy from light soils, and good both in quality and quantity from fertile loams. It is therefore a suitable crop for loams, peaty soils, and sandy soils. Nearly half the ash of the potato plant consists of potash; this is a larger proportion than is found in the ashes of any other farm-plant, and this accounts for the fact that kainite has 334 PRINCIPLES OP AGRICULTURE. a better-marked effect as a special manure on the potato crop than on any other. Though classed as a root-crop, potatoes are not roots but a form of underground stem called tuber^ the same as Jerusalem artichokes, which also are tubers. The ' eye ' of a potato is really a leaf-bud. 551. The Carrot (Dauciis carota) is restricted in cultiva- tion. There are many varieties (fig. 122), generally white or red. The carrot requires a deep soil free from stones, and Copyright S. « S. Fig. 122.— Sutton's Improved Red Intermediate, Giant White Belgian, and Long Red Altrincliam Carrots. grows best on light soils. Carrot seed is very minute, disc- shaped, and granular, and has hair-like appendages, which make them cling together and difficult to sow. They also take a long time to germinate. The Belgian white carrot is the usual field-crop variety. Parsnips (Pastinaca sativa) is less cultivated than carrots and requires good land. In the Channel Islands it is a ROOT-CROPS — SWEDE, POTATO. 335 favourite crop and feed for cows and pigs. It is a hardy plant, and can be left in the ground during winter, and when fed to cows, good rich butter is obtained with a good flavour and colour. 552. Though we have now noted the crops common to British agriculture, it must not be supposed that those named represent all the farm-crops known. A sugar-cane grower or a tea-planter is as much a farmer as the man who grows wheat or turnips. We will simply note some of these crops, so that the agricultural student may see that if the principles of agriculture are founded on ascertained facts and natural laws, they do not cover and explain the growth of the farm-crops common to Britain only, but also all crops which are grown in any part of the world. These crops are, for example, rice, maize, millet, broom-corn, sorghum, vines, hops, and olives ; the sweet potato, yams, sugar-cane, tobacco, arrowroot ; tea, coff'ee, cocoa, ginger, cotton, pine-apples ; flax, hemp, jute, sun- flowers, ground-nut and castor-oil plants, osiers, manilla hemp, wattles, opium poppy, indigo, date palms, turmeric, bananas, and cinnamon. Questions.— 1. AVliat is the difference between a swede and a common turnip ? 2. Name some other root-crops besides turnips. 3. Name some farm-crops not grown in the United Kingdom. PLANTS OF THE GARDEN AND ORCHARD. CrUCIFER^ — CUCURBITACE^— Cauliflower aiul Broccoli (Brassica Cucumbers {Cucumis sativvs). oleracea). Vegetable MarroAVS (Cucurbita ovifera). Radish (Raphamts sativus). Pumpkins (Cucurbita maxima). Horse Radish (Cochlearia armoracia). Melons (Cucumis meld). Water-cress {Nasturtium officinale). Gourds (Cucumis), species. RlBESIACE^ — UmBELLIFER^ — Gooseberry (Ribes Grossularia). Celery (Apiuno graveolens). Red Currant (Ribes rubrum). Parsley [Petroselinum sativum). B^ack Currant (Ribes nigrum). Caraway [Carum Carui). Coriander {Coriandrum sativum). 336 PRINCIPLES OF AGRICULTURE. Rosacea— Apple {Pyrus mahis). Pear (Pyrus communis). Cherry (Pruiius Cerasus). Damsons {Prumis domedica). Greengages (Primus domestica). Apricots (Prviuts arnuniacci). Peaches (Ainygdahis Persica). Nectarines (Amygdalns Persica). Ahnonds (Prunus Amygdalns). Strawberry (Fragaria vesca). SOLANACEiE — LABIAT^ Tomato {Lycopersicum Rosacea — continued : Raspberry (Paibiis RUens). Blackberry (Rtibtis frutieosus). Dewberry (Rubits ccesius). Composite — Endive (Cichorium Endivia). Lettuce (Lactuca virosa). Jerusalem Artichoke (i/e7ianf7t?/s tuber- osus). Artichoke {Cynara Scolym^is). Chenopodiace^ — [Salvia officinalis). Beetroot (Beta vulgaris). esculentum). Mint [Mentha,], species. Thyme [Thymus serpyl- lum^. Spinach [Spinacia oler- acea). POLYGONACE.« — Rhubarb (Rheum), species. LlLIACE^ — Asparagus (Asparagus officinalis). CHAPTER LXIX. HARVESTING AND OTHER MACHINERY. 553. Crops that are grown on the farm have to be cut and threshed before the farmer derives any benefit. For- merly the sickle and scythe were used in reaping; now harvesting-machines (reaping and binding) are employed. Fig. 123. —A. Jack & Sons' Caledonian Buckeye Mower. These machines are manual-delivery reapers, self-delivery reapers, and binders. HARVESTING AND OTHER MACHINERY. 337 The manual-delivery reaper simply cuts the corn, and the sheaves have to be laid off by liand. The mower, Fig. 121.— Howard's Patent Reliance Reaper. which is used for cutting grass (fig, 123), is similar to a manual-delivery reaper, exeept that it has three travelling Fig. 125. — Howard's Reaper and Binder. wheels. The self-delivery reaper (fig. 124) is a more in- tricate implement than the manual-delivery, as the sheaves V 338 PRINCIPLES OF AGRICULTURE. are laid off' by revolving arms or sails. But the most in- tricate machine of all is the binder, Avliich is the result of the application of a larger number of mechanical principles than are to be found in any other farm implement. The reaper and binder (fig. 125) cuts the grain and packs it Fig. 126. — Australian Harvester. into a sheaf, which the ' binder ' encircles with a cord, and this the 'knotter' ties and cuts, and, when free, two arms throw the sheaf off the machine. The stripper, of which the Australian harvester (fig. 126) is the most improved pattern, is the principal mode of harvesting grain in some hot, dry '<^ climates. By this machine the corn is ' stripped ' — that is, the ears are taken off and the Rf. 127 straw leit standing to be burnt on the ground. But besides gather- ing the ears, the harvester threshes and partially dresses the corn, so that the grain is bagged on the ;nachine, HARVESTING AND OTHER MACHINERY. 339 Fig. 128. — Howard's New Lever Horse-rake. ready for an early market. The macliine is useful where there is no need or demand for straw, and the system is carried out in the drier sections of Australia. The ' stripper ' in principle is like the reaping- machine Pliny says was used in Gaul, and shown in fig. 127. 5 5 4. The horse-rake (fig. 128) has taken the place of the hand-rake, and is generally used for gathering grass and unsheaved corn into rows, while the haymaker or tedder has superseded the fork for tossing and tedding hay (fig. 129). This machine has simply a number of tines attached to heads fixed to the axle, and as they re- volve they catch and toss the hay. 5 5 5. Two kinds of machines are in use for con- veying produce to market and other purposes in husbandry — wagons and carts — and of these there are several varieties. Wagons with four wheels, and drawn by two or more horses, are acknowledged to be best adapted for conveying great loads to a great distance, and Fig. 129.— Howard's Patent Simplex Haymaker. 340 PRINCIPLES OP AGRICULTURE. Fig. 130. that is their principal merit. For all ordinary purposes connected with husbandry, the one-horse cart with two wheels is preferable. The Scotch cart, as it is called, is a most convenient and useful implement ; and to add to its uses, it may be ren- dered serviceable for carting hay or straw by placing a movable frame on its sides, as represented in fig. 130. The Scotch cart (without tlie frame) is suited for conveying any kind of material — dung, turnips, grain in sacks, &c. — and usually carries from eighteen to twenty-two hundredweight, when drawn by only one horse ; with a horse in trace, the weight may be augmented. In Scotland, all grain for market is carried in these one-horse carts, and to any distance. On such occasions, one driver can take charge of two carts. The Cart wheel is an important part of the cart as an implement. It should be 'dished;' that is, when laid flat on the ground, the rim should not be on the same level as the solid centre. The hub and the tire are the important parts of a wheel, and by ' dishing,' so long as the tire lasts, any pressure transmitted through the spokes only wedges the felloes m.ore tightly together. 556. When the crop is thoroughly dr}', it is led home to the stack-yard, and built into stacks so constructed as to afford com- plete shelter from the weather (fig. 131). These are less used now than formerly, as in days gone past they were largely used for keeping grain over the summer, which then paid well; now there is little to be gained by such a practice in Great Britain. In England, stacks are sometimes constructed on a timber platform raised Fig. 131. HARVESTING AND OTHER MACHINERY. 341 upon stones, and over the stack the framework of a perfect barn is placed, which can either be tiled or thatched. 557. Threshing is the next operation, and it used to be performed with i\\Q flail, but is now done by threshing-mills, which can be driven by water, horse, or steam power, according to cir- cumstances, rig. 132 is an illus- tration of a threshing- machine now common, to which is attached a straw - trusscr, an adaptation of the sheaf-bind- iug apparatus. ^ig. 132.- Howard's Patent Straw-trusser. Steam threshing- machines may be fixed or portable. Fixed boilers, engines, and mills, with the necessary buildings, are to be found on all large farms in the United Kingdom, and in iig. 133 the process of steam-threshing by portable machinery is shown, including the stacking of the straw by means of the elevator or stacker. Hay and straw compressors have also lately come into use, and by them a bulky light material like straw is put into small space, and can be better handled, stored, and transported. 558. Winnowing is a process performed by the aid of whid, by which the cliaff of corn is separated from the grain. Winnowing-machines, or fanners, are frequently attached to threshing-mills, and they are a necessary appendage to every farm, either in conjunction with the threshing-mill, or separately. Some farmers winnow their grain by hand-fanners (fig. 134). By the process of win- nowing, chaff, bits of straw, the seeds of weeds, and other HARVESTING AND OTHER MACHINERY. 343 refuse, are separated from the grain ; and the different quahties of grain are also separated from each other, by Fig. 134. — HornsLy's Now Australian Winnower. which it is rendered more vahiable than when the good and bad are mixed togetlier. Barley under- goes a process called hummel- ling, by which the awns are broken off from the grain. The machine is com- posed of a verti- cal spindle enclosed in a cylinder, and furnished with arms Fig. 135. A. Jack & Sons' Caledonian Potato -digger. Ui PRINCIPLES OF AGRICtLTtJRfi. wliicli act upon the grain. It is sometimes attached to the threshing-mill, and sometimes driven by a separate power. The grain is put in at the top of the cylinder, and as it passes through, the awns are broken off by being struck by the arms attached to the spindle. 559. Anotlier form of harvesting machinery is the potato-digger. Figs. 135 and 136 arc two kinds of the Fig. 136.— Powell's Patent Potato ivUb^i. machine. The potatoes are unearthed by a deep-cutting blade or broadshare, which raises the plant, while a revolv- ing wheel with projecting arms or forks throws them out. Questions.—]. What is the difference between a manual delivery reaper and a binder ? 2. What is a fanner ? For what purpose is it used ? 3. What is an elevator and a trusser ? 4. What are the hub, spokes, felloes, and tire of a wheel ? Conclusion. 345 CHAPTER LXX. CONCLUSION. 560. We have now taken a survey, brief and superficial, of the many subjects included in agriculture which a young student sliould recognise as of importance, and which he will require to study carefully when more advanced. In agricultural science, care must be taken not to fall into narrow and contracted views, as in many points theories alter as our knowledge increases. In agriculture, theory is the outcome of practice. Take, for example, the explana- tion for clover- or bean-sick land. First, it was explained by the mineral theory (the chemist's view) — namely, that the soil had become deficient in a food constituent, and therefore the plant could not grow. Xext came De Candolle's theory (the botanist's view) that plants left an excreta in the soil, which after a time became noxious to the plant and it could not subsist, but that other plants could live in this excreta ; so that one class of plants could live on the excreta of another class, but not on that of its own class. N^ow the bacteriologist is advancing his views that it is owing to the absence of soil-germs which the plant needs to live healthy, that the ' sickness ' of the soil is due. We must be very careful and not confuse agricultural chemistry, or agricultural botany, or agricultural biology with agriculture. The production of crops, and the breeding and feeding of animals, are the two objects of agriculture, and agricultural science teaches Iww this is done, while chemistry, botany, &c. give their assistance in forming a 346 PRINCIPLES OP AGRICULTURE. rational and logical explanation of the tclnj and the where- fore. 561. We must also take a broad view regarding the principles of agriculture. Principles to be true must be world-wide, and not confined. Suppose we were trained in Scotland and went out to Australia, yet if we have been thoroughly drilled in the principles of agriculture we should not be at a loss (though we have left a farm where the ex- perience of generations has brought culture to a high state of perfection), although we have now simply to cut out of the forest a farm for ourselves, doing with our own labour what had been done for us in Scotland centuries ago by our an- cestors. We would find the native grasses, herbs, shrubs, and trees offer a good index to the quality of the soil, as it is impossible to find a heavy growth of rich herbs and grasses upon poor land. Eesidence and observation would teach us regarding the seasons and climate that Australia is not a land of perpetual summer, subject to terrific floods and excessive droughts. Further, chemical analysis would show that the soils are stubborn — that is, they yield up their plant-food slowly, besides showing marked deficiencies in the alkaliesj alkaline earths, and phosphates. Again, obser- vation of plant growth would teach us how to clear land of timber by ringing or ring-barking the trees, and local circumstances will lead us to put up our fences, Avhich would probably be classified under one of the following heads : wire, post and rail, chock and log, billabong, stubb, double post and rail, Virginian snake or zigzag, basket and brush. Kegarding rotations, it is not necessary that the crops grown in Europe should be taken as long as the crops grown follow out the principles of crop rotation. Thus a rotation could be wheat, potatoes, maize, grass; or it might be maize (or barley), cotton, grass, grass, or any other rotation of plants that soil, climate, and markets permit. CONCLUSION. 347 662. We must bear in mind that the study of agriculture is not intended to qualify us as professional land and plant doctors, but rather to assist us to carry out intelligently the daily round of farm practice and procedure. Take the soil of any field or paddock and ask yourself the question — What are the physical properties and chemical nature of this soil 1 (See section 3, Soil Physics ; and section 4, Soil Chemistry.) Next answer the general question — Hoav do plants grow and feed 1 (Sections 1 and 2, Plant Composition and Plant Life.) Then take any of our farm-crops (section 7, Crops) and answer the question — How does this special plant grow and feed, and how far does the soil meet its requirements? And the last question is — How can I by manuring (section 6, Manures), or by tillage (section 5, Tillage), meet both the necessities and requirements of soil and plant, so that I can produce a crop which will yield me a profitable return ? A good farmer is a man who can not only grow crops successfully and economically, but can harvest his crops securely, and can market them advantageously. 348 INDEX. [The figures in this Index refer to the paragraphs only.] Absorptive power of soils. .161-162, 224 Acids 55,57 Acme harrow 299 Active and available i)lant-food.l71, 241 Adulterations of grass seeds 516-526 Agents weathering rocks 218 Agricultural chemistry, 4, 39, 560 ; elements of, 16 ; theories 560 Agriculture 1, 2, 560-562 Alfal fa 536 Alkalies 58 Alluvial soils 141, 156, 212-215 Alsike or Swedish clover 534 Aluminium and alumina — 5, 41, 47, 78, 165, 183 Ammonia 19, 22, 38, 165, 244 Analysis of peaty soil, 150 ; of fertile and infertile soil, 234 ; of wheat- grain 87 Animal agents, 221 ; guano, 410 ; kingdom, 7, 10 ; organs 11 Annual meadow-grass 526 Annuals 109-112 Apatite 415 Aqueous rocks 217 Arable land 510 Argillaceous soil 183 Arterial drainage 342 Artificial manures 383 Aruba phosphate 415 Ash constituents of plants — 70, 74, 77, 78, 95, 486-487 Aspect of land 198 Atmospheric air — 19, 22, 23, 30, 206, 242-243 Austi'alian agriculture, 199 ; har- vester 553 Autumn cultivation 267, 269 Bacteria 226-227 Bare fallow 223, 268, 270, 460 Barley, 463-486, 500-504 ; manures. 503 Barrenness in soils 172, 178-180 55 Basic cinder, slag, or phosphate. . . .419 Beans 405, 467-486, 527-528, 530 Be