'ARY PRINCIPLES 
 
 Bjll 
 
 I 
 
 IFIC AGRICULTURE 
 
 T. LUPTON
 
 UQS K|4GBJUES, Cflii, 
 
 UNIVERSITY of CALIFORNJ/ 
 
 A 
 
 1 i. -' 
 
 LOS ANGEI.KS 
 UKRARY
 
 THE 
 
 ELEMENTARY PRINCIPLES 
 
 OF 
 
 SCIENTIFIC AGRICULTURE. 
 
 N. T. 
 
 PROFESSOR OF CHEMISTRY 
 
 SHKW.E 
 
 ' 
 
 V 
 
 
 
 NEW YORK : CINCINNATI : CHICAGO 
 
 AMERICAN BOOK COMPANY.
 
 PRIMER SERIES. 
 
 SCIENCE PRIMERS. 
 
 HUXLEY'S INTRODUCTORY VOLUME. 
 
 ROSCOES CHEMISTRY. 
 
 STEWART'S PHYSICS. 
 
 GEIKIE'S GEOLOGY. 
 
 LOCKYER'S ASTRONOMY. 
 
 HOOKER'S BOTANY. 
 
 FOSTER AND TRACY'S PHYSIOLOGY AND 
 
 HYGIENE. 
 
 GEIKIE'S PHYSICAL GEOGRAPHY. 
 LUPTON'S SCIENTIFIC AGRICULTURE. 
 JEVONS'S LOGIC. 
 
 SPENCER S INVENTIONAL GEOMETRY. 
 JEVONS'S POLITICAL ECONOMY. 
 TAYLOR S PIANOFORTE PLAYING. 
 PATTON'S NATURAL RESOURCES OF THE 
 
 UNITED STATES. 
 
 HISTORY PRIMERS. 
 
 WENDEL S HISTORY OF EGYPT. 
 FREEMAN'S HISTORY OF EUROPE. 
 FYFFE'S HISTORY OF GREECE. 
 CREIGHTON'S HISTORY OF ROME. 
 MAHAFFY'S OLD GREEK LIFE. 
 WILKINS'S ROMAN ANTIQUITIES. 
 TIGHE'S ROMAN CONSTITUTION. 
 ADAMS S MEDIAEVAL CIVILIZATION. 
 YONGE'S HISTORY OF FRANCE. 
 GROVE'S GEOGRAPHY. 
 
 LITERATURE PRIMERS. 
 
 BROOKE'S ENGLISH LITERATURE. 
 WATKINS'S AMERICAN LITERATURE. 
 DOWDEN S SHAKSPERE. 
 ALDEN S STUDIES IN BRYANT. 
 MORRIS S ENGLISH GRAMMAR. 
 MORRIS AND BOWEN'S ENGLISH 
 
 GRAMMAR EXERCISES. 
 NICHOL'S ENGLISH COMPOSITION. 
 PEILE'S PHILOLOGY. 
 J EBB'S GREEK LITERATURE. 
 GLADSTONE'S HOMER. 
 TOZER S CLASSICAL GEOGRAPHY. 
 
 LUPTON SCI. ACR. 
 
 COPYRIGHT, 1880. BY D APPLETON & CO. 
 W. P. 5
 
 PREFACE. 
 
 THE following communication explains the rea- 
 son that induced the author to present to the public 
 this little work on " The Elementary Principles of 
 Scientific Agriculture " : 
 
 NASHVILLE, TENN., December 17, 1879. 
 In accordance with Chapter CLXXXVI., Acts 
 of the General Assembly of Tennessee, approved 
 March 27, 1879, which directs "that the Superinten- 
 dent of Public Instruction and the Commissioner 
 of Agriculture shall be constituted a commission to 
 procure the preparation of, or the designation of a 
 work on the Elementary Principles of Agriculture 
 which shall be taught in the public schools of the 
 State, as are the other studies prescribed in the 2ist 
 section of the Public School Law," the undersigned 
 have " procured the preparation " of a work as here- 
 in described, by Professor N. T. Lupton, Professor 
 of Chemistry, Vanderbilt University; and, having 
 carefully examined the MS., hereby approve the
 
 4 PREFACE. 
 
 same and adopt it, to be taught in the public 
 schools of the State, in accordance with the express 
 terms of said act. 
 (Signed) . 
 Commit- ( LEON TROUSDALE, State Superintendent, 
 
 is- j L 
 " ( J. 
 
 sioners. [ J. B. KILLEBREW, Com. of Agriculture. 
 
 In response to this demand for the introduction 
 of the " Elementary Principles of Agriculture " into 
 the regular course of study in the public schools, 
 the author has endeavored to present the subject 
 in clear, concise language, avoiding technical terms, 
 except where scientific accuracy required their use. 
 As the principles discussed are of universal applica- 
 tion, this little work is designed for general use, being 
 adapted to every section where agriculture is taught 
 and practiced as a science. It is believed that intel- 
 ligent farmers and planters will find it sufficiently plain 
 and practical for profitable reading and study. 
 
 The attention of teachers is called to a few sim- 
 ple experiments in the Appendix, to which reference 
 is made in the text by corresponding figures inclosed 
 in parentheses. The performance of even a few ex- 
 periments will add greatly to the interest of pupils 
 in the facts and principles presented.
 
 CONTENTS. 
 
 CHAPTER SECTIONS PAGE 
 
 I. THE DEVELOPMENT OF SCIENTIFIC AG- 
 RICULTURE i-n 7 
 
 /flj THE ORIGIN, COMPOSITION, AND CLAS- 
 
 SIFICATION OF SOILS i . 1 2-49 12 
 
 III. THE COMPOSITION OF PLANTS . . 50-70 27 
 
 IV. COMPOSITION AND PROPERTIES OF THE 
 
 ATMOSPHERE 71-82 35 
 
 V. THE SOURCES OF PLANT-FOOD, AND HOW 
 
 OBTAINED 83-95 39 
 
 VI. THE IMPROVEMENT OF SOILS . . 96-110 45 
 VII. THE USE OF MANURES OR FERTILIZERS 111-157 51 
 JVJIL, MINERAL FERTILIZERS .... 158-176 70 
 IX. ROTATION OF CROPS .... 177-188 79 
 X. THE SELECTION AND CARE OF LIVE- 
 STOCK 189-200 84 
 
 APPENDIX go 
 
 QUESTIONS 95
 
 ELEMENTARY PRINCIPLES 
 
 OF 
 
 SCIENTIFIC AGRICULTURE. 
 
 2. / 
 CHAPTER I. 
 
 THE DEVELOPMENT OF SCIENTIFIC AGRICULTURE. 
 
 1. AGRICULTURE is both a science and an art. 
 As an art, it teaches how to cultivate the soil, make 
 and use fertilizers, take care of stock, and do what- 
 ever is necessary for the successful management of 
 a farm. As a science, it explains the growth of 
 plants and animals, and the principles upon which 
 the practical operations of farming depend. As an 
 art, it tells what to do ; as a science, it explains tha 
 reasons for what is done. 
 
 2. Agriculture, like other sciences, was practised 
 as an art long before the principles upon which it is 
 based were understood. As an industrial pursuit, it ; 
 has always been the first in importance. This is 
 owing to the fact that man's necessities compel him to 
 cultivate the soil. While the earth of its own accord
 
 8 SCIENTIFIC AGRICULTURE. 
 
 produces enough food for the support of the lower 
 animals, man is forced to earn his bread by the sweat 
 of his brow. 
 
 3. In the early ages of the world, the population 
 was small, and the wants of men so few that very lit- 
 tle cultivation of the soil was required. The rivers 
 and forests supplied, in a great measure, both food 
 and clothing, until the increase of population origi- 
 nated necessities and luxuries which could only be 
 satisfied by increased cultivation. 
 
 4. Although agriculture, as an art, has been prac- 
 tised to some extent by all nations, and in every age 
 of the world, its progress as a science has been very 
 slow. In fact, sciences of recent origin have made 
 much greater progress and are at this day more gen- 
 erally understood. There are men even now who 
 say that practical and scientific farming are very 
 different ; in other words, that agriculture is no sci- 
 ence at all. This is because they do not understand 
 its principles, or have a false notion of what scientific 
 agriculture really is. 
 
 5. There are several reasons for the slow prog- 
 ress or growth of agriculture as a science. In the 
 first place, the dignity and importance of the pursuit 
 were not fully recognized until within recent times. 
 It is true that, in every age of the world, some good 
 and great men have been farmers. We read in his- 
 tory of Cincinnatus leaving his plow at the call of his 
 country, and of Putnam deserting his field of agri- 
 cultural labor for one of military glory, and even of
 
 DE VELOPMENT. g 
 
 Washington retiring to Mount Vernon to spend the 
 closing years of a noble life in the quiet occupation 
 of a farmer. We read, too, of Plato, and Pliny, and 
 Columella, and even of Cicero, living at times on 
 their farms and writing on subjects connected with 
 farming operations. These noted men, however, did 
 not practise farming as a profession, as a perma- 
 nent business, but rather as a relaxation from the 
 cares of political life. To accomplish great results 
 in any department of science requires that we make 
 it more than a recreation, more than a pastime. 
 It must be the study of a lifetime. 
 
 6. Again, agriculture has made slow progress as 
 a science, because it is closely connected with and 
 dependent on other sciences which are themselves of 
 recent origin. A good farmer must know something of 
 Botany, the science of plants, whether he finds it out 
 by observation or learns it from books, that he may 
 understand the character of the various products of 
 the soil, and be enabled to adapt his mode of culti- 
 vation to the nature of his crop. 
 
 7. The farmer must know, at least practically, 
 something of Zoology, the science of animals, that he 
 may procure and raise such stock as will be of most 
 service to himself, and command good prices in the 
 market. He must be something of a geologist, that 
 is, must know enough of Geology, the science that 
 treats of the structure and formation of the earth, 
 its soil and rocks, to enable him to understand the 
 nature of soils, and be able to judge of their value by
 
 10 SCIENTIFIC AGRICULTURE. 
 
 mere inspection. If not a mechanic himself, the me- 
 chanic arts must be understood by those who furnish 
 him with plows and wagons and other farming im- 
 plements. The science of Physics, which treats of 
 the general properties of bodies, and the causes 
 such as light, heat, and electricity that modify these 
 properties, is also important ; and, finally, the farmer 
 ought to have some knowledge of Chemistry, in order 
 to understand the constitution of soils, and plants, 
 and fertilizers, and to enable him to adapt them 
 to each other, and, when necessary, to determine 
 what ought to be added to a soil to make it produce 
 a good crop. 
 
 8. We do not mean to say that the farmer or 
 planter must be skilled in all these sciences, but he 
 should have at least a general acquaintance with 
 them if he would practise farming to the best advan- 
 tage. To the farmer, they are all profitable subjects 
 for study, because they are closely connected with 
 his profession, and are, in fact, the foundation upon 
 which the science of agriculture is based. 
 
 9. Perhaps the most important practical results 
 to agriculture have been derived from the science of 
 Mechanics and that of Chemistry. The progress in 
 the mechanic arts is seen when we compare the 
 farming implements now in use with those of for- 
 mer times. The rough, uncouth wooden plow has 
 given place to various forms of neat, easy-running 
 plows partly or wholly of iron, and even these have 
 given place in some countries to the gang and steam
 
 DEVELOPMENT. tl 
 
 plow, which do the work of a dozen old-fashioned 
 implements. The sickle has given place to the cra- 
 dle, the cradle to the reaper, the scythe to the mower, 
 the old tedious process of separating cotton-seed 
 from the fiber by hand, to the cotton-gin, and a great 
 many other mechanical improvements which the in- 
 ventive genius of the nineteenth century has given 
 to the world. 
 
 10. Among the benefits derived from chemistry 
 may be mentioned : 
 
 1. It teaches the composition and qualities of 
 soils, of plants, of the atmosphere, of fertilizers. 
 
 2. It determines the kind and quality of food 
 that different plants need for strong, healthy growth. 
 
 3. It shows how to manufacture fertilizers, and to 
 make use of all sorts of refuse matter in the prepara- 
 tion of food for plants. 
 
 4. It explains the action of light, heat, and other 
 agencies in promoting growth, and, in a word, un- 
 folds all the conditions of fertility. 
 
 IT. The chemist in his investigations proceeds 
 to analyze the soil, and plant, and air, and fertilizers, 
 that he may understand their nature and the rela- 
 tions they sustain to each other ; and we propose to 
 inquire into the results of these investigations, and 
 show in few words what modern science teaches of 
 the composition and use of these substances with 
 which the farmer and planter have so much to do.
 
 12 SCIENTIFIC AGRICULTURE. 
 
 CHAPTER II. 
 
 THE ORIGIN, COMPOSITION, AND CLASSIFICATION OF 
 SOILS. 
 
 12. THE earthy matter in which plants grow is 
 called the soil. It consists of finely divided parti- 
 cles of rock mixed with organic matter. The organic 
 matter comes chiefly from the decay of plants, and 
 forms generally a very small portion of the soil. It 
 can be easily burned off, leaving the mineral portion, 
 which consists of disintegrated or finely crumbled 
 rock (i). The earth is supposed by geologists to har^ 
 once been a mass of melted matter. As it cooled 
 down, a crust was formed upon which condensed 
 moisture falling as rain wore away the solid rock, 
 being aided in its corroding action by heat and other 
 agencies, until the pulverized or finely divided sur- 
 face was in proper condition to produce the plant. 
 
 Soils consist of a small amount of organic 
 matter mixed with rock which has been re- 
 duced to a fine state of division by mechanical 
 and chemical agencies. 
 
 13. Mechanical agencies are such as merely 
 alter the form or appearance of bodies without 
 changing their character, like the grinding or rub- 
 bing of rocks together, whereby they are broken into 
 small pieces. Each little piece has the same prop- 
 erties as the large mass. Chemical agencies are
 
 SOILS. T3 
 
 such as alter the real nature of bodies, as in the 
 rusting of iron and the burning of wood. The rust 
 has different properties from the metallic iron, and 
 the gases and ash formed in burning are very differ- 
 ent from the original wood. In such cases, chemical 
 action has brought about the change. Both these 
 agencies are all the time at work upon the rocks, and, 
 though they are generally slow in their action, vast 
 results are finally produced. 
 
 14. The geologist includes under the term rock 
 all soils and loose material, clays, and gravel, as well 
 as the large solid masses which compose the earth. 
 The disintegrating, or crumbling action by which 
 soils are formed is always going on, plants and ani- 
 mals doing a great deal toward bringing about the 
 changes that are produced. The most powerful 
 agencies in the crumbling of rocks are air and wa- 
 ter. Water not only wears away rocks and reduces 
 them to powder by mechanical action, but it dis- 
 solves them all in a greater or less degree. This 
 solvent action is greatly increased by the air which 
 it contains. Water also soaks into soft rocks and 
 runs into holes and crevices, where freezing it ex- 
 pands, and forces masses and particles of rock asun- 
 der. One great advantage of deep, thorough culti- 
 vation is that air and moisture may penetrate the 
 soil, and continue their disintegrating or crumbling 
 action upon the particles of rock of which the soil 
 is composed, thus setting free the plant-food and pre- 
 paring it as proper nourishment for the hungry plant
 
 I 4 SCIENTIFIC AGRICULTURE. 
 
 15. The elements of a soil vary with the kind of 
 solid rock from which it was originally formed. A 
 disintegrated sandstone, or limestone, or slate, or 
 granite, will each produce a soil of peculiar cha'rac- 
 ter. Very often the soil rests upon the rock from 
 which it was formed. Sometimes, however, it has 
 been carried away and deposited at a long distance 
 from the parent rock. Such deposits form what are 
 called alluvial soils, and are generally found in creek 
 and river bottoms (2). 
 
 1 6. The great difference in the quality and value 
 of soils results mainly from a difference in the rela- 
 tive quantity of certain elements present. The total 
 absence of any of the essential elements of plants is 
 rare. Notwithstanding the great variety of mineral 
 and vegetable substances, the whole mass of the 
 earth and everything upon it is composed of few 
 elements, or simple substances (3). 
 
 17. The number of elements certainly known is 
 sixty-five; several others have been announced 
 recently, but their existence is yet in doubt. Five 
 of these, oxygen, hydrogen, nitrogen, chlorine, and 
 fluorine, are gases, and two, bromine and mercury, 
 are liquids at the ordinary temperature of the air, 
 while all the others are solid. By reducing the 
 temperature and applying great pressure, the gases 
 can be changed to liquids, and the liquids can be 
 converted into solids. There are no permanent 
 gases ; even oxygen, hydrogen, and nitrogen have 
 been made to assume the liquid form.
 
 SOILS. I5 
 
 18. The farmer and planter are concerned with 
 only fourteen or fifteen of these elements, because 
 only this number enter into the composition of soil-, 
 generally, and are concerned in the growth of plant*- 
 These are as follows : 
 
 Non-metallic Elements. Metallic Elements, 
 
 1. Oxygen. i. Potassium. 
 
 2. Hydrogen. 2. Sodium. 
 
 3. Nitrogen. 3. Calcium. 
 
 4. Carbon. 4. Magnesium. 
 
 5. Silicon. 5. Aluminium. 
 
 6. Sulphur. 6. Iron. 
 
 7. Phosphorus. 
 
 8. Chlorine. 
 
 To these may be added manganese, iodine, and 
 fluorine, which are sometimes present in minute 
 quantities. 
 
 19. Oxygen is by far the most abundant of the 
 elements. It forms about one half of the solid crust 
 of the earth, eight-ninths of all the water, and one- 
 fifth of the atmosphere. This element is easily pre- 
 pared by heating in a glass tube or flask either mer- 
 curic oxide (commonly called red oxide of mercury), 
 or potassium chlorate. Heat separates the oxygen 
 from these compounds. It can easily be collected 
 in suitable vessels and its properties examined. If a 
 small quantity of manganese dioxide (black oxide of 
 manganese) be mixed with the potassium chlorate, the 
 oxygen will be given off at a lower temperature. (4).
 
 1 6 SCIENTIFIC AGRICULTURE. 
 
 20. Oxygen is an invisible gas without taste or 
 smell. It is called a supporter of combustion because 
 wood, coal, oil, gas, and other substances burn in it. 
 If the oxygen be pure they burn with great brilliancy. 
 Combustion, such as takes place in our fireplaces, 
 stoves, and lamps, is the result of chemical union be- 
 tween the oxygen of the air and the carbon and hy- 
 drogen of the fuel. The bright sparks that fly from 
 the blacksmith's anvil are particles of iron uniting 
 with oxygen. 
 
 21. Oxygen unites to form compounds with all. 
 the known elements except fluorine. These com- 
 pounds are called oxides. The compounds of oxy- 
 gen with some of the metals were originally named 
 by merely changing the termination um or him of 
 the metal into a. These names are still in common 
 use. Thus : 
 
 Potassium hydroxide is often called potassa or potash. 
 Sodium hydroxide " soda. 
 
 Magnesium oxide " magnesia. 
 
 Aluminium oxide " alumina. 
 
 Calcium with oxygen forms lime ; silicon forms 
 silica or pure white sand. According to the new. 
 system of naming oxides, the name of the metal 
 comes first with the word oxide immediately after. 
 
 22. Oxygen sometimes unites slowly and gradu- 
 ally with other elements without producing light or 
 intense heat, as when wood decays or iron rusts. 
 These are cases of oxidation, and the final results 

 
 SOILS. I7 
 
 are the same whether the action takes place slowly or 
 rapidly. This process of slow oxidation is constantly 
 going on in the bodies of animals. When they breathe, 
 the air enters the lungs, where the oxygen it contains 
 is taken up or absorbed by the blood, and carried 
 throughout the body. Animals cannot live without 
 oxygen. It is also necessary to the growth of plants. 
 
 23. Hydrogen is another abundant element. It 
 forms one ninth by weight of water and enters into 
 the composition of all plants and animals. It can 
 be prepared easily by the action of dilute sulphuric 
 or hydrochloric acid on zinc or iron. If some scraps 
 of either of these metals be placed in a wineglass 
 and a little acid poured over them, effervescence will 
 be produced by the escape of the hydrogen (5). 
 
 24. Hydrogen is the lightest substance known. 
 Like oxygen it is an invisible gas without color, taste, 
 or smell, but unlike oxygen it will burn when brought 
 in contact with flame. The flame of burning hydro- 
 gen is of a pale-blue color and intensely hot (6). 
 The result of the combustion is water (7). Sixteen 
 pounds of oxygen unite with two pounds of hydro- 
 gen to form eighteen pounds of water. 
 
 25. Water, which is formed by the chemical 
 union of the two elements just mentioned, is one of 
 the most abundant and important compounds in 
 nature. It is easily converted into vapor, \vhich, ris- 
 ing from the surface of the earth in an invisible form, 
 is afterward condensed into rain, and dew, and 
 frost. It dissolves solid, liquid, and gaseous sub-
 
 iS SCIENTIFIC AGRICULTURE. 
 
 stances, and in this way carries food to the roots of 
 plants (8). All natural waters, such as are found in 
 springs, wells, rivers, and lakes, contain in solution 
 more or less mineral matter derived from the soil. 
 Rain-water is the purest, as it contains nothing in 
 solution except what it gets from the air as it falls 
 through it. 
 
 26. Nitrogen is found in the atmosphere in 
 large quantity, and also in plants and animals. It 
 forms four-fifths of the volume of the air. The most 
 convenient way to prepare nitrogen is to remove the 
 oxygen from air by means of phosphorus (9). Other 
 substances can also be used for the removal of the 
 oxygen. 
 
 27. Nitrogen is a colorless gas with no taste or 
 smell. It neither burns nor dpes it support combus- 
 tion. Animals cannot live in it, and yet it is not 
 poisonous. It has no power to sustain life, merely 
 serving in the atmosphere to dilute the oxygen. The 
 three gases just mentioned are easily distinguished 
 by means of a lighted taper. Oxygen will not burn, 
 but will make the taper burn with great brilliancy ; 
 hydrogen will put out the taper, but will burn itself 
 with a pale-blue flame; nitrogen will neither burn 
 nor will it support the flame, but put it out at once. 
 
 28. Ammonia is a very important compound of 
 nitrogen and hydrogen. It is formed when am- 
 monium chloride (sometimes called sal-ammoniac) 
 is rubbed with common lime, and is a gas of strong, 
 pungent odor (10). It unites with acids, destroying
 
 SOILS. I9 
 
 their sour taste. Water absorbs about seven hundred 
 times its volume of this gas, and in this condition 
 it is commonly called hartshorn. Ammonia is 
 an alkali that is, it neutralizes acids and restores 
 vegetable colors, like litmus, that have been made red 
 by means of an acid. 
 
 29. Ammonia is formed naturally by the decay 
 of animal and vegetable matter, as in manure-piles. 
 Its odor can be detected in stables, or where organic 
 substances containing nitrogen are undergoing de- 
 composition. As a gas it exists in minute quantities 
 in the atmosphere, .and finds its way into plants 
 through their roots. 
 
 30. Nitrogen and oxygen unite to form several 
 oxides, one of which when combined with water is 
 known as nitric acid. This is a very strong acid of 
 intensely sour taste. It corrodes or destroys the 
 flesh, and acts upon nearly all the metals, forming 
 with them a class of compounds, called nitrates. 
 One of these, potassium nitrate, is known as nitre or 
 saltpetre ; and another, sodium nitrate, goes by the 
 name of Chili saltpetre. Both of these nitrates are 
 used as fertilizers (n). 
 
 31. Carbon is an element that exists in three 
 distinct forms. Charcoal, coke, and lampblack are 
 varieties of the first; graphite, or plumbago, com- 
 monly known as black lead and used for mak- 
 ing lead-pencils, is the second ; and the diamond, 
 which is pure crystallized carbon, the third and most 
 valuable form. When wood is heated in a close ves-
 
 20 SCIENTIFIC AGRICULTURE. 
 
 sel or burned in a covered heap, the black residue is 
 chiefly carbon. This element forms the greater por- 
 tion of woody substances and enters largely into the 
 composition of all organic matter. Sugar contains 
 42 per cent, of carbon, spirits of turpentine 88 per 
 cent. The black smoke of a candle or lamp is car- 
 bon in a finely divided state (12). 
 
 32. Carbon dioxide, or carbonic acid gas, 
 is a compound of carbon and oxygen that exists in 
 small quantities in the air, and is always formed 
 when carbon burns. It is a heavy, poisonous gas 
 that is formed during respiration, combustion, fer- 
 mentation, and decay. While it poisons animals, it 
 is an important food for plants, as will be shown 
 hereafter. If a little hydrochloric acid be poured 
 on a piece of marble or limestone, the effervescence 
 produced is caused by the escape of this gas (13). 
 It will extinguish a burning taper. 
 
 33. Silicon is an element found in common sand 
 and quartz. It is very abundant, forming about one- 
 fourth of the solid part of the earth, but very diffi- 
 cult to separate from the oxygen with which it is near- 
 ly always combined. Some chemists doubt whether 
 it is a necessary constituent of plants. It is certainly 
 found in the stems of grass, wheat, corn, and in vari- 
 ous kinds of vegetation. 
 
 34. Sulphur is a well-known substance of yellow 
 color that burns with a pale-blue flame and suffocat- 
 ing odor. In burning, it unites with the oxygen of 
 the air to form sulphur dioxide, which is used to de-
 
 SOILS. 21 
 
 stroy bad odors and also for bleaching straw bonnets, 
 hats, and other goods (14). Sulphur in combination 
 with oxygen and hydrogen forms sulphuric acid, or 
 "oil of vitriol," one of the strongest of the acids. 
 This acid forms compounds known as sulphates, as 
 calcium sulphate, or gypsum, and magnesium sulphate, 
 or Epsom salts (15). 
 
 35. Phosphorus is a soft, slightly yellow solid, 
 that gives off a white smoke when exposed to the 
 air and takes fire very easily. This white smoke is 
 caused by the slow burning of the phosphorus (16). 
 This element forms a large percentage of the bones 
 of animals, and is found in soils and in plants, espe- 
 cially in the seeds. Phosphorus takes fire so easily in 
 the air that it must be kept under water. It is used 
 for making matches. When the end of a match is 
 rubbed against a rough surface, enough heat is pro- 
 duced to set fire to the phosphorus; this inflames the 
 sulphur on the match, and the sulphur sets fire to the 
 wood of which the match is made (17). 
 
 36. Phosphoric acid is a compound of phos- 
 phorus with oxygen and hydrogen (18). When cal- 
 cium takes the place of hydrogen in this acid it forms 
 calcium phosphate, or bone phosphate, the chief con- 
 stituent of bones. This acid forms a large class of 
 salts called phosphates. As animals get their food 
 from plants and plants their food from the air and 
 soil, it is necessary for soils to contain phosphorus. 
 When a deficiency of this element does exist in a 
 soil, it is usual to supply it by means of bones.
 
 22 SCIENTIFIC AGRICULTURE. 
 
 37. Chlorine is a heavy gas of a yellowish-green 
 color, found only in combination with other elements. 
 In combination with hydrogen it forms hydrochloric 
 acid, formerly called muriatic acid. If this acid be 
 heated with manganese dioxide, the chlorine will be 
 separated. It is poisonous when breathed. It will 
 destroy organic coloring matters and bad-smelling 
 gases, and hence is used for bleaching, and as a dis- 
 infectant or purifier of air (19). Common salt is a 
 compound of sodium and chlorine. This element 
 is found in the ash of plants and also in soils. 
 
 38. Iodine, a dark-colored solid that forms a 
 beautiful violet vapor when heated, and bromine, 
 a dark-red liquid, are found in combination with 
 other elements in some plants. In chemical proper- 
 ties they are similar to chlorine (20). Fluorine is 
 the most difficult to prepare of all the elements. 
 It is described as a gas, and exists in small quan- 
 tities in the teeth of animals, and in other por- 
 tions of the body, and also in some plants and 
 minerals. 
 
 39. Potassium is a soft metal, lighter than water. 
 It unites with oxygen so readily that it has to be kept 
 under the surface of naphtha, a liquid that has no 
 oxygen in it. If thrown on the surface of water, or 
 placed on a piece of ice, it takes fire and burns with 
 a beautiful violet-colored flame (21). In combina- 
 tion with hydrogen and oxygen, it forms caustic pot- 
 ash. All the acids contain hydrogen. The salts of 
 potassium are formed by replacing the hydrogen of
 
 SOILS. 23 
 
 an acid with this metal. Some of these salts are found 
 in soils and in the ashes of plants. 
 
 40. Sodium is a soft metal very much like po- 
 tassium in appearance and in properties. It also 
 must be kept under naphtha, but will not take fire 
 on water, unless it be held in one place, or the water 
 be warmed. It spins around over the water, decom- 
 posing it, and forming caustic soda (22). It forms a 
 large number of salts. Common salt is sodium chlo- 
 ride, and is found in all salt springs, in the ocean, and 
 in soils, and the ashes of plants. Caustic soda and. 
 caustic potassa, or potash, are called alkalies. They 
 destroy the flesh, neutralize acids, and color red lit- 
 mus-paper blue (23). In these respects they are 
 similar to ammonia. They are used to make soap : 
 caustic potash to make soft soap, and caustic soda to 
 make hard soap. 
 
 41. Calcium is a metal very hard to separate 
 from its compounds. With oxygen it forms com- 
 mon, unslaked lime. Marble, and limestone, and 
 chalk, are calcium carbonates, which on being heat- 
 ed lose carbon dioxide, and are changed into lime. 
 Gypsum, or land plaster, is calcium sulphate, a valu- 
 able fertilizer. Spring and well water very often 
 contain these salts in solution. 
 
 42. Magnesium and aluminium are hard, white 
 metals, the former a constituent of dolomite, or mag- 
 nesian limestone, and some other rocks ; the latter is 
 found in all clay and slate rocks. The metal mag- 
 nesium burns with great brilliancy and is sometimes
 
 24 SCIENTIFIC AGRICULTURE. 
 
 used for lighting up caves (24). Aluminium has 
 been used to some extent for ornamental and other 
 purposes, but it is so difficult and expensive to sep- 
 arate from its compounds that it has not come into 
 general use. 
 
 43. Iron is a common metal with which every- 
 body is familiar. Its ores, such as hematite and 
 limonite, are abundant, and are used in immense 
 quantities for the manufacture of this useful metal. 
 It is found in all soils forming the coloring matter 
 of clays, and exists in a great variety of minerals. 
 Manganese is a metal very much like iron in its chem- 
 ical properties, but much more difficult to separate 
 from its ores.* 
 
 44. In giving the composition of a soil it is usual 
 to state the percentage weight of the metallic oxides 
 and acid-forming oxides, as it is known that the ele- 
 ments do not exist in the soil in a free state. The 
 process of analyzing a soil, that is, of finding out its 
 constituents, is easily understood in theory, but to 
 perform the analysis requires some practice and 
 skill in chemical work. Such analyses are not so 
 useful to the farmer as was once supposed, since the 
 condition of the elements in the soil has more to 
 do with its fertility than quantity. 
 
 45. The following analysis of a fertile soil will 
 give some idea of the relative quantity of the con- 
 stituents usually found : 
 
 * For a more extended description of these elements the 
 student is referred to works on chemistry.
 
 SOILS. 2 
 
 Per cent. 
 
 Potassium oxide 0.2 
 
 Sodium oxide 0.4 
 
 Calcium oxide, or lime 5.9 
 
 Magnesium oxide, or magnesia o.8j 
 
 Iron oxide, or ferric oxide 6.1 
 
 Aluminium oxide, or alumina 5.7 
 
 Manganese oxide o.i 
 
 Silicon oxide (silica) 64.8 
 
 Sulphuric acid, or sulphur trioxide 0.2 
 
 Phosphoric acid, or phosphorus pentoxide 0.4^ 
 
 Carbonic acid, or carbon dioxide 4.0 
 
 Chlorine 0.2 
 
 Organic matter 9.7 
 
 Loss 1.4 
 
 Total 100.0 
 
 The proportion of some important constituents, 
 as potassium oxide, phosphoric acid, etc., is very 
 small, but the smallest would amount to several tons 
 per acre. 
 
 46. Silica, or sand, is the chief substance in a great 
 many soils. Clay, a compound of silica and alumina 
 with small quantities of other elements, is also abun- 
 dant in most soils ; so are lime and iron oxide. The 
 amount of organic matter is quite variable. In some 
 soils it reaches 15 or 20 per cent, while in others it 
 is less than i per cent. The total absence of any 
 of the constituents mentioned above, except perhaps 
 aluminium oxide and manganese, would render the 
 soil unproductive for ordinary crops. Those in least 
 abundance, as potassium oxide and phosphoric acid,
 
 2 6 SCIENTIFIC AGRICULTURE. 
 
 are most likely to be deficient, and in such cases 
 they must be supplied by the use of fertilizers or 
 manures. 
 
 47. The great quantity of sand in most soils and 
 its presence in all have suggested the propriety of 
 classifying soils according to the amount of sand 
 they contain, as follows : 
 
 1. Pure clay, from which no sand can be re- 
 moved by washing. 
 
 2. Strong clay, when the soil contains from 5 
 to 20 per cent, of sand. 
 
 3. Clay loam, when it contains from 20 to 40 
 per cent, of sand. 
 
 4. Loam, from 40 to 70 per cent, of sand. 
 
 5. Sandy loam, from 70 to 90 per cent, of 
 sand. 
 
 6. Light sand, more than 90 per cent, of sand. 
 It is easy to classify soils in this way by merely 
 
 washing out the sand and weighing it (25). 
 
 48. When soils contain a large amount of calcium 
 carbonate, they are said to be calcareous, or marly ; 
 and, when a very large percentage of organic matter, 
 they are said to be peaty, or are called vegetable 
 mold. The presence of a large quantity of clay 
 makes a soil sticky when wet, and causes it to hold 
 moisture a long time, hence such soils are said lo be 
 heavy ; a large quantity of sand gives the opposite 
 property, that is, of not retaining moisture, and 
 hence these are said to be light. 
 
 49. The soil proper is the surface layer down to
 
 THE COMPOSITION OF PLANTS. 
 
 27 
 
 where a change in the character of the material takes 
 place, generally from six to ten inches and beneath 
 this is the sub-soil. Deep cultivation increases the 
 depth of the soil, and allows air and moisture to 
 enter, and the roots of plants to penetrate farther in 
 search of food. 
 
 CHAPTER III. 
 
 THE COMPOSITION OF PLANTS. 
 
 50. THE following ten elements are always found 
 in plants, and are believed to be absolutely essential 
 to their growth : 
 
 Non-metallic. Metallic. 
 
 1. Carbon. 7. Potassium. 
 
 2. Hydrogen. 8. Calcium. 
 
 3. Oxygen. 9. Magnesium. 
 
 4. Nitrogen. 10. Iron. 
 
 5. Sulphur. 
 
 6. Phosphorus. 
 
 Four others, sodium, manganese, silicon, and 
 chlorine, are generally found, and in marine, or sea 
 plants, iodine and bromine. Traces of fluorine have 
 also been found, and sometimes minute quantities of 
 Jithium, caesium, and rubidium, and a few other ele- 
 ments. 
 
 51. A great many analyses and experiments have 
 been made by chemists to find out just what ele-
 
 2 g SCIENTIFIC AGRICULTURE. 
 
 ments enter into the structure of plants, and whether 
 they are all really necessary for plant-growth. The 
 results of these investigations, as given in the last 
 section, show what sort of food plants must have in 
 order to grow. Aluminium, an element found in all 
 soils and the base of all clay, does not enter into 
 plants. As animals derive their food from plants or 
 from each other, the same elements, except silicon, 
 enter into the composition of both. 
 
 52. If a plant be heajted up to the boiling-point 
 of water, it loses a large part of its weight by the 
 escape of water which it contains, and becomes dry. 
 In turnips and cabbages, nine-tenths, and in potatoes 
 three-fourths of their weight is water which can be 
 driven off by heat. Even in cured hay and fodder, 
 from one-sixth to one-tenth is water. If the dried 
 plant be exposed to a red heat, it will take fire and 
 the greater part be consumed. The small portion 
 left is called the ash, and is generally a fine white 
 or gray powder (26). 
 
 53. The portion of a plant that burns is chiefly 
 carbon combined with some hydrogen and oxygen, 
 and a little nitrogen. These four elements are some- 
 times called organic elements, because they form by 
 far the larger part of organic bodies. In the process 
 of combustion, while these elements disappear, it 
 must not be supposed that they are destroyed. They 
 merely enter into new combinations with the oxygen 
 of the air, forming chiefly carbon dioxide and watery 
 vapor, which float off unseen in the atmosphere.
 
 THE COMPOSITION OF PLANTS. 
 
 29 
 
 54. When plants are burned with free access of 
 air, the sulphur and phosphorus are oxidized, and 
 remain in the ash with the metals. Chlorine and 
 silicon are also found in the ash. This ash, or inor- 
 ganic matter, varies in quantity from about one-half 
 to one per cent, in some kinds of wood to from 
 15 to 18 per cent, in tobacco. The following table 
 shows about the average percentage of ash in a 
 number of vegetable products : 
 
 Percentage of Ash in Dried Products. 
 Cotton, lint i.o Red clover 6.8 
 
 " seed 8.9 Cabbage 8.0 
 
 Wheat, grain 1.9 Irish potatoes 4.3 
 
 Turnips 10.0 
 
 Tobacco 15-18 
 
 straw 5.0 
 
 Indian corn 1.5 
 
 The elements that enter into the composition of 
 the ash are given in the following table : 
 
 Percentage Composition of the Ash of Plants. 
 
 
 WHEAT. 
 
 Indian 
 corn. 
 
 Pota- 
 toes. 
 
 Redclo- 
 i-erhay. 
 
 Tobac- 
 co.* 
 
 Grain. ! Straw. 
 
 
 31.54 is. 16 
 2.66 i. co 
 
 12.10 4.00 
 
 3.14 6.82 
 trace. 1.02 
 
 48.50 3.20 
 
 0.08 5.78 
 1.88 65.34 
 o.io o 60 
 
 37-95 
 3-oo 
 7-5 
 3-4 
 0.40 
 
 44-80 
 
 1.50 
 1-45 
 trace. 
 
 61.60 
 
 1. 00 
 
 5.00 
 
 2.40 
 
 0.85 
 17.67 
 
 6 25 
 
 I. CO 
 
 2.23 
 
 31.86 
 2.16 
 
 12. l6 
 
 3 1 - ? 
 0.66 
 
 9.00 
 
 3-3 
 6.71 
 
 3-33 
 
 32-63 
 3 .8r 
 
 12 10 
 40.15 
 
 3-74 
 4.02 
 2.60 
 0.86 
 
 
 Magnesium oxide, or magnesia. . . . 
 Calcium oxide, or lime 
 Iron oxide 
 Phosphorus pentoxide, or phos- | 
 
 Sulphur trioxide, or sulphuric acid. 
 Silicon dioxide, or silica 
 
 
 
 100.00 100. CO ICO. CO ICO. CO 100.00 ICO.OO 
 
 * Average of several analyses of Kentucky tobacco made in 
 the laboratory of Vanderbilt University by Messrs. Hobbs and 
 Wooldridge.
 
 3 o SCIENTIFIC AGRICULTURE. 
 
 55. The elements heretofore mentioned as form- 
 ing the material of plants are sometimes called ulti- 
 mate elements, because they are the simplest forms 
 of matter into which plants can be separated, or re- 
 solved. What are called the proximate elements, 
 or principles, are compound substances, such as 
 starch, sugar, gum, oil, cellulose, or woody fibre, etc. 
 While there are a large number of these, each spe- 
 cies of plant having its peculiar principle, the 
 greater number can be included under the follow- 
 ing groups. 
 
 56. Amylaceous and saccharine substances, 
 such as starch, sugar, cellulose, or woody fibre, and 
 gum. These are composed of only three elements, 
 carbon, hydrogen, and oxygen. The woody fibre, or 
 cellulose, forms the greater part of many plants, and 
 usually consists of small tubes sticking to each other. 
 Cotton fibre is nearly pure cellulose. It is contained 
 in all plants, in the stems, leaves, roots, and seeds. 
 It has the same elements in the same proportion 
 as starch, and differs in these respects very slightly 
 from sugar. It can be converted into one kind of 
 sugar, glucose, by boiling with dilute sulphuric 
 acid. 
 
 57. Pectose substances, like the jellies and 
 pulp of fruits, and of some roots, as the turnip, beet, 
 and onion. These substances are closely related to 
 woody fibre, and are easily changed into it by the 
 plant. 
 
 58. Vegetable acids, such as tartaric acid found
 
 THE COMPOSITION OF PLANTS. 31 
 
 in grapes, citric acid in lemons, and malic acid in 
 apples. These vegetable acids are numerous, but 
 all have the same elements, carbon, hydrogen, and 
 oxygen, that are found in sugar. 
 
 59. Fats and oils, such as are found in olives, 
 cotton-seed, flax-seed, etc. These are composed of 
 the same elements as sugar, but have proportionally 
 less oxygen. Turpentine, resin, and different kinds 
 of wax, are included in this group. 
 
 60. Albuminoid, or protein bodies, which dif- 
 fer from the group mentioned, in having nitrogen 
 as a constituent, and in some cases sulphur and 
 phosphorus. Albumen is found nearly pure in the 
 white of an egg, and a similar substance is contained 
 in the juices of plants. The term " albumen " is used 
 by botanists to mean any nutritive material found in 
 the seeds of plants without reference to its chemical 
 composition. Chemists apply the word only to sub- 
 stances containing nitrogen, and in this sense it is 
 here used. Gluten, a sticky substance found in 
 flour, belongs to this class, and vegetable casein, 
 similar to the white curd of milk, found in legu- 
 minous plants, such as the pea and bean. 
 
 61. Notwithstanding the great variety of these 
 proximate principles, and their great difference in 
 physical and chemical properties, they are composed 
 of only a few elements. A knowledge of their chemical 
 constitution has very greatly simplified the changes 
 which take place in the growth and maturity of plants, 
 and shown that a very slight alteration in chemical
 
 3 2 SCIENTIFIC AGRICULTURE. 
 
 constitution will convert a disagreeable or tasteless 
 fruit into one that is sweet and delicious. 
 
 62. Starch and sugar differ from each other very 
 slightly in the number and proportion of their con- 
 stituent elements, while starch, cellulose, and gum 
 are the same in these respects. How the internal 
 structure or arrangement of these elements causes a 
 change in properties, we do not know. Starch forms 
 the larger portion of the seeds of most plants, and 
 especially of those used as food. Wheat, corn, rice, 
 and potatoes, when dry, are about two-thirds starch. 
 
 63. Grape-sugar differs from starch by one equiva- 
 lent of water, that is, by the addition of a little water 
 chemically combined, starch becomes sugar. This 
 change takes place in seeds to some extent in the 
 process of sprouting, and is taken advantage of in the 
 manufacture of beer and whisky from barley and 
 corn. A lock of cotton, or even some sawdust, can 
 be changed into sugar suitable for manufacturing al- 
 cohol by dissolving it in strong sulphuric acid, dilut- 
 ing with water, and boiling for some time. 
 
 64. Every green leaf is a tiny laboratory, where 
 by the aid of the sun's rays those changes are made 
 which give us wood, and starch, and sugar, and gluten, 
 and gum. To make these the plant uses carbon di- 
 oxide and ammonia, and water and other substances, 
 which enter the plant as food. 
 
 65. The following table gives the composition of 
 various crops :
 
 THE COMPOSITION OF PLANTS. 
 
 33 
 
 
 Water. 
 
 Albu- 
 min- 
 oids. 
 
 Fat. 
 
 Non-ni- 
 trojen- 
 tzed ex- 
 tractive 
 matter. 
 
 Woody 
 fibre. 
 
 Starch. 
 
 i 
 Ash. 
 
 Grasses (hay) 
 
 15-0 
 
 9.4 
 
 2.6 
 
 38.8 
 37.2 
 
 28.5 
 24.8 
 
 
 5-7 
 5-7 
 
 Wheat 
 
 
 
 
 
 
 
 I 7 
 
 Oats. .... 
 
 
 
 60 
 
 
 
 56.5 
 
 3.0 
 
 
 
 
 7.0 
 
 
 5.2 
 
 61.4 
 
 1.9 
 
 
 
 
 
 
 
 60.2 
 
 2.3 
 
 Rye . . . 
 
 
 
 
 
 8.0 
 
 64.0 
 
 I.O 
 
 Rice 
 
 
 5-3 
 
 I.O 
 
 
 2.5 
 
 767 
 
 0.7 
 
 
 6 6 
 
 
 
 
 
 14.0 
 
 9.0 
 
 Potatoes 
 
 7S-5 
 
 2.1 
 
 0.7 
 
 
 2.1 
 
 18.6 
 
 I.O 
 
 66. The ash constituents, though small and vari- 
 able in quantity, are of prime importance in the 
 growth of the plant ; and just here we find the whole 
 theory of fertilizing. The moisture and volatile com- 
 pounds formed during combustion float off unseen 
 in the air when a plant is burned or decays, and, by 
 this same air where these compounds always exist, 
 they are carried to other plants and serve as proper 
 food, while the ash constituents can not be thus trans- 
 ported. Every plant removed from the soil carries 
 with it the elements of this ash, and, as some of these 
 elements exist in minute quantities, the soil is sure 
 to become exhausted where means are not used to 
 have them restored. 
 
 67. The old system of carrying away and never 
 restoring these necessary elements has well been 
 called by Liebig a system of spoliation. Some 
 elements, such as iron and silicon, and, in miny soils, 
 calcium and sodium, are so abundant that, practically, 
 they may never become deficient, and yet they may
 
 34 
 
 SCfEN TIFIC A GRICUL TURE. 
 
 not be in a condition to be readily used as food by the 
 plant. To remedy this condition, either mechan- 
 ical means must be used, such as repeated plow- 
 ing, deep and thorough, to bring about exposure to 
 air, and rain, and sunshine, and frost ; or chemical 
 means, as the application of lime and various salts 
 which supply food directly, or which exert a decom- 
 posing action, and thus prepare the food which al- 
 ready exists in the soil and render it suitable for use. 
 
 68. Phosphorus and potassium, which are gen- 
 erally in minute quantities, as well as other elements 
 when deficient, must be supplied, or the vigorous 
 growth of plants whose structure requires these ele- 
 ments and thio includes all of our valuable crops is 
 an utter impossibility. As well might the carpen- 
 ter dispense with nails in the construction of a house? 
 or the tailor with thread in making a coat, as the 
 farmer dispense with these essential elements in the 
 growth of his crop. 
 
 69. As soils are of great variety, their composition, 
 or character, should be determined, and the deficien- 
 cy pointed out, if any exists, before an attempt be 
 made to remedy the defect. While chemistry teaches 
 the farmer the cause of the exhaustion of his soil and 
 shows how this can be prevented, it must not be held 
 responsible for the failures resulting from the use of 
 the many mixtures which are sold under various 
 names as fertilizers. 
 
 70. The means used for furnishing plants with 
 the elements necessary for their growth, that is, for
 
 THE ATMOSPHERE, 
 
 35 
 
 keeping a soil fertile, whether mechanical or chemi- 
 cal, must be guided by sound judgment. While prac- 
 tical observation and experience teach us that lands 
 do wear out by continued cultivation and removal 
 of crops, chemistry explains the cause, and points out 
 the remedy. This may be by the purchase of con- 
 centrated fertilizers, or by the use of such fertilizing 
 materials as already exist or can be produced on 
 every farm. This subject will be discussed in a sub- 
 sequent chapter. 
 
 CHAPTER IV. 
 
 COMPOSITION AND PROPERTIES OF THE ATMOSPHERE. 
 
 71. THE atmosphere from which plants obtain a 
 large portion of their food is a mixture of oxygen and 
 nitrogen in the proportion of about one-fifth of the 
 former to four-fifths of the latter, with a small quan- 
 tity of carbon dioxide, a trace of ammonia, a vari- 
 able quantity of watery vapor, and traces of a few 
 other gases resulting from combustion and decay 
 Its composition by volume may be stated as follows 
 
 Nitrogen 77-95 
 
 Oxygen 20.61 
 
 Watery vapor 1.40 
 
 Carbon dioxide ." 0.04 
 
 Ammonia ) 
 
 ... \ traces 
 
 Hydrogen carbide . . ) 
 
 ( Hydrogen sulphide. > 
 
 In towns \ \ traces 
 
 ( Sulphurous oxide. . . \ 
 
 Sulphi 
 Total. . . 100.00
 
 36 SCIENTIFIC AGRICULTURE. 
 
 72. These constituents, though gaseous and in- 
 visible, can be separated and measured by the chem- 
 ist as surely and definitely as the farmer can mea- 
 sure his corn and wheat, or the planter weigh his 
 cotton and tobacco. Two of these, carbon dioxide 
 and ammonia, though in very small quantities, are 
 sufficient for the ordinary growth of plants. They 
 are all so nicely intermingled, so uniformly mixed, 
 that dry air, no matter where collected, is found to 
 possess essentially the same composition. 
 
 73. Watery vapor, as above stated, is a variable 
 constituent of the atmosphere. It rises continually 
 from the surface of the land, as well as from every 
 lake, and river, and ocean, and comes to us again in 
 gentle showers which the cool currents of air con- 
 dense, or in dew-drops which settle by night on leaf 
 and flower. Beautifully harmonious are the laws 
 and operations of nature, and especially that law by 
 which the vapor of water so gently and continuously 
 ascends from the earth's surface and, condensing, 
 falls to be again vaporized after it has performed its 
 part in the support of animal and vegetable life. 
 
 74. The study of chemistry has revealed the part 
 that each of these constituents of the atmosphere 
 performs in the economy of nature. Nitrogen is 
 negative in its character, being indifferent toward 
 entering into combination with other elements, while 
 oxygen is active and energetic in supporting com- 
 bustion, and in sustaining animal life. Our bodies, 
 like stoves, are consumers of carbon and oxygen, and
 
 THE ATMOSPHERE, 
 
 37 
 
 produce in a similar manner the gas known as car- 
 bonic acid, or carbon dioxide. This gas is poisonous 
 to animals when it exists in any considerable quan- 
 tity in the air, but is absolutely essential to the 
 growth of plants. 
 
 75. Carbon dioxide consists of carbon and oxy- 
 gen, and is generated in all cases of ordinary com- 
 bustion, in putrefaction, fermentation, and decay. 
 It is also a product of respiration, and would soon 
 accumulate in sufficient quantity to destroy animal 
 life, were it not for the fact that it is absorbed by the 
 leaves of trees and plants, there deprived of its car- 
 bon, and pure oxygen restored to the air whence it 
 came (28). 
 
 76. Every one has observed the soft, porous tex- 
 ture of the under surface of the leaves of plants; 
 through these pores the carbon dioxide is inhaled as 
 it floats in the atmosphere, and under the influence 
 of sunlight the process of digestion takes place with- 
 in the plant whereby the carbon is retained as food, 
 and the oxygen exhaled, thus preserving the purity 
 of the air. 
 
 77. The relative amount of carbon dioxide in the 
 atmosphere is only about one twenty-fifth of one per 
 cent., and yet it is enough for the purposes of vegeta- 
 tion. A distinguished chemist says, " The gigantic 
 trees which adorn the forests of tropical regions with 
 the dense pine woods of more northern zones, and 
 the abundant though less conspicuous vegetation 
 of temperate climes, all derive their stock of carbon
 
 3 8 SCIENTIFIC AGRICULTURE. 
 
 from this small but essential constituent of the at- 
 mosphere." 
 
 78. Ammonia exists in the air in even more mi- 
 nute quantities than carbon dioxide, so minute that 
 only the most delicate tests can indicate its pres- 
 ence, and the most sensitive balance would not be 
 affected by the quantity in a room of ordinary size, 
 and yet it is of essential value to all kinds of vege- 
 tation. 
 
 79. A close study of the nature and composition 
 of the atmosphere shows that it is admirably adapted, 
 by its physical and chemical properties, to the wants 
 of animals and plants. " It conveys to them their 
 nourishment and life ; it tempers the heat of summer 
 with its breezes; it binds down all fluids, and pre- 
 vents their passing into a state of vapor ; it supports 
 the clouds, distills the dew, and waters the earth with 
 showers ; it multiplies the light of the sun, and diffuses 
 it over earth and sky ; it feeds our fires, turns our 
 machines, wafts our ships, and conveys to the ear all 
 the sentiments of language and all the melodies of 
 music." 
 
 80. Science teaches us that Infinite Wisdom has 
 shown, in these invisible atmospheric agencies at 
 work around us, the same skill and benevolence, 
 the same goodness and power, as in the more mani- 
 fest displays of divine energy. Silently but surely 
 they accomplish their appointed work of contribut- 
 ing directly to the nutrition of organic bodies, and 
 by their action upon solid substances continually
 
 THE SOURCES OF PLANT-FOOD. 
 
 39 
 
 prepare material to take its proper place in the build- 
 ing up of animal and vegetable structures. 
 
 81. The atmosphere acts upon both organic and 
 inorganic matter so as to reduce it to simpler forms- 
 As soon as an animal or plant dies, by contact with 
 the air its elements quietly but surely undergo a 
 change, recombining to form new and simpler com- 
 pounds capable of entering again into organic bodies. 
 
 82. Knowing the composition of the soil, of 
 plants, of air, we are prepared to study their relations 
 and the laws of growth and development in plants. 
 
 CHAPTER V. 
 
 THE SOURCES OF PLANT-FOOD AND HOW OBTAINED. 
 
 83. THE earth and atmosphere are, of course, the 
 only possible sources of food for plants, but the in- 
 teresting questions arise, What portion of food does 
 each furnish ? and how is it taken up and used by the 
 plant ? If we include hydrogen, which is one of the 
 elements in watery vapor and in ammonia, there are 
 four elements in air, viz., oxygen, nitrogen, carbon, 
 and hydrogen. A great many experiments have been 
 made to find out whether these four elements enter 
 directly from the air into plants, through the leaves, 
 or are taken in by the roots from the soil. 
 
 84. Carbon, the most abundant element in or- 
 ganic substances, cannot enter the plant in a pure
 
 40 SCIENTIFIC AGRICULTURE. 
 
 state, as it is perfectly insoluble. In the gaseous 
 form, as carbon dioxide, it is absorbed in large quan- 
 tities by the leaves, and it also enters through the 
 roots. By the action of sunlight this gas is decom- 
 posed in the green leaf, the carbon retained, and the 
 oxygen restored to the air. This change cannot take 
 place without the influence of sunlight, and hence 
 plants grow much more rapidly in the daytime than at 
 night. It is believed, by those who have studied the 
 subject closely, that all the carbon contained in farm 
 crops is derived from the atmosphere. 
 
 85. Hydrogen and oxygen enter in the form 
 of water through the roots, and carry with them the 
 various soluble matters of the soil that are needed 
 for growth. Hydrogen also enters in the form of 
 ammonia, which is a compound of nitrogen and hy- 
 drogen, and as hydrogen compounds formed by the 
 decomposition of organic matters in the soil. In the 
 same manner oxygen, in combination with carbon 
 and with hydrogen and other elements, is absorbed 
 in large quantities. 
 
 86. Nitrogen is also taken in as food by both 
 leaves and roots, but always in combination. This 
 element forms nearly four-fifths of the atmosphere, 
 and yet, as free nitrogen, it does not contribute in 
 the least to vegetable growth. The whole of the 
 nitrogen is obtained from compounds of ammonia 
 and from nitrates. 
 
 87. Plants contain very little nitrogen, generally 
 from one half to three per cent. This, however, is
 
 THE SOURCES OF PLANT-FOOD. 4I 
 
 as necessary as those elements that enter largely 
 into their composition. One ton of hay contains 
 about thirty pounds of nitrogen, a small quantity 
 proportionally, but in one hundred tons it amounts 
 to a great deal. The stimulating effect of guano and 
 similar manures is due mainly to the nitrogen they 
 contain in the form of ammonia and its salts. While 
 the atmosphere may contain ammonia enough to 
 meet the ordinary demands of vegetation, it has not 
 enough to supply the extraordinary demand of an 
 immense crop in a limited time. 
 
 88. The four elements just mentioned are some- 
 times called organic elements, because they form 
 much the larger part of all organic bodies. The re- 
 maining constituents, called inorganic elements, are 
 found in the ash of plants, and are always taken 
 in as soluble matter through the roots. The question 
 arises, In what manner? Before answering this ques- 
 tion, it will be well to examine the structure and use 
 of the different parts of a plant. 
 
 89. The main parts of a plant are the root, the 
 Stem, and the leaves (29). The root spreads through 
 the earth as the stem does through the air. The 
 seed contains an initial steml that is, the beginning 
 of a stem, with food enoughi^Kart it to growing. It 
 requires for germination or fir^growth, air, warmth, 
 and moisture. The moisture which is first absorbed 
 causes the seed to swell, oxygM^enters, a chemical 
 change takes place in the elenrcnts composing it 
 whereby the germ, or little plant, gradually enlarges,
 
 42 SCIENTIFIC AGRICULTURE. 
 
 the covering bursts, and the radicle, or rootlet, ap- 
 pears, and buries itself in the earth, while the little 
 stem or plumule, as it is called, rises to the surface of 
 the ground in search of sunlight. Nature has stored 
 up in the seed enough material to supply the growth 
 thus far, but henceforth its food must come from the 
 soil and atmosphere. This, in some mysterious way, 
 through the influence of sunlight, it is enabled to 
 take in and digest. 
 
 90. The root once started, divides and subdi- 
 vides, sending out branches in every direction and 
 hunting industriously in the soil for nourishment, 
 while the stem and leaves do the same in the at- 
 mosphere. The leaves are in some sense the lungs 
 of the plant, while the roots are its mouths. The 
 length to which the roots sometimes extend is as- 
 tonishing, and they really seem to have a kind 
 of instinct that guides them to their proper food. 
 Those which find proper nourishment enlarge and 
 multiply rapidly, while those that do not, die or re- 
 main undeveloped. For a plant to be thrifty, it 
 must have plenty of suitable food, and have it near 
 at hand. It cannot, like an animal, run about in 
 search of what it needs^^Hiigh it will extend its roots 
 to a long distance if ^Hfssary to get suitable mate- 
 rial for growth. 
 
 91. Schubert, a German agriculturist, made an 
 excavation in a &e\djto the depth of six feet, and di- 
 rected a stream of^water against the vertical wall of 
 soil until it was washed away, so that the roots of
 
 THE SOURCES OF PLANT-FOOD. 
 
 43 
 
 plants growing in it were laid bare. Roots were ex- 
 posed in this way in a field of rye, also in one of 
 beans, and in a bed of garden-peas, which were 
 found to present the appearance of a mat of white 
 fibres to a depth of four feet from the surface of the 
 ground. He found the roots of winter wheat as deep 
 as seven feet in a light sub-soil forty-seven days 
 after sowing. Another German, who has studied 
 the subject, calculated the total combined length 
 of the roots of a vigorous barley plant in a rich 
 garden soil to be one hundred and twenty-eight 
 feet, and in a coarse-grained, compact soil eighty 
 feet. 
 
 92. The absorbing surface of roots is greatly in- 
 creased by very small root-hairs which are lost as 
 the roojis become old. It was once supposed that 
 the ends, or tTps of roots consist of delicate tissue, 
 or organs called " spongioles," through which alone 
 
 rption of food takes place, but such is not the 
 se ; no organ or structure of the kind exists. 
 
 93. Agricultural writers distinguish three kind of 
 roots, viz., soil roots, water roots, and air roots. 
 Nearly al^P^ our useful plants have soil roots which 
 perish if kept for a length of time in air or water, 
 while stfSfS"* plants, as rice for instance, have roots 
 which gan grow either in soil or water. The com- 
 mon mulberry and China tree will extend a portion 
 of their roots down to the bottom of a well thirty or 
 more feet in depth, and mat over the bottom com- 
 pletely, while the cornstalk will put out air roots at
 
 44 
 
 SCIENTIFIC AGRICULTURE. 
 
 a joint above the ground, which extend until they 
 reach and penetrate the soil. 
 
 94. It was once supposed that roots have the 
 power of excretion, the reverse of absorption, but 
 Johnston says, " In the light of newer investigations 
 touching the structure of roots and their adaptation 
 to the medium which happens to invest them, we 
 may well doubt whether agricultural plants in the 
 healthy state excrete any solid or liquid matters from 
 their roots." The food that enters a plant through 
 the roots must be in a state of solution. There is 
 no doubt that plants have, to a certain extent, 
 the power of selection. We know that plants grown 
 on the same soil and under the same conditions do 
 not have the same elements in equal proportions. 
 
 95. From the facts stated in reference to roots, 
 the importance of deep, thorough preparation of 
 land before planting, and of shallow cultivation after 
 the crop has been well started, is evident. Should 
 the soil, however, become hard and baked, it would ' 
 be good policy to cultivate deeply even at the risk 
 of destroying rootlets, which under such circum- 
 stances are necessarily sickly, that new and vigorous 
 ones may put forth and have mellow soil through 
 which to penetrate. No fixed rule can be laid down 
 to be rigidly followed in all cases. The intelligent 
 farmer or planter should be guided by the indica- 
 tions of the season, and the condition of his crop, in 
 the use of means necessary to meet an emergency. 
 Even the bird, though governed by instinct, modifies
 
 THE IMPROVEMENT OF SOILS. 
 
 45 
 
 at times the shape of its nest to adapt it to peculiar 
 surroundings, and so the farmer must use his reason 
 in cultivating his crop. He should be guided, not 
 by " cast-iron " rules, but by correct principles, and 
 modify his mode of cultivation to suit each particu- 
 lar case. 
 
 CHAPTER VI. 
 
 THE IMPROVEMENT OF SOILS. 
 
 96. DEAD matter has no power in itself, so far as 
 we know, to change into an organized structure. It 
 has the power, under certain circumstances, of form- 
 ing crystals of great beauty, but in these forms there 
 is no life. This life-principle, every seed or germ 
 has within itself, and when called into activity it un- 
 folds the plant. Exactly what this life-principle is, 
 we know not, but we can study the conditions of 
 plant-growth, and explain to some extent the changes 
 which take place in the swelling of the seed by heat 
 and moisture, and its partial decomposition into 
 simpler forms, whereby energy is imparted in some 
 mysterious way, sufficient to push the rootlet down- 
 ward, and the slender stem upward to the sunlight. 
 
 97. The connection between the rays of the sun 
 drunk in by the leaves of plants and the absorption 
 of food by their roots, the appropriation of this food 
 and its assimilation or use in the production of bark, 
 and wood, and leaves, and fruit, has not yet been ex-
 
 46 SCIENTIFIC AGRICULTURE. 
 
 plained, and perhaps never will be. Chemistry, how- 
 ever, has taught us how to stimulate the process, and 
 has shown us that there is no change of one element 
 into another, but a simple use of that which is in reach 
 of the plant, whether it be in the air above or in the 
 soil beneath. 
 
 98. If it be absurd to suppose, as everybody must 
 admit, that one element can change into another, the 
 practical conclusion follows that, to insure fertility, 
 the necessary elements which compose the particular 
 plant under cultivation must exist in the soil, or its 
 growth is impossible. As simple and self-evident as 
 this statement may appear, there has ever been a 
 vague notion in the minds of men that nature has 
 some power of changing elements, or of supplying 
 them as needed for the growth of vegetation. 
 
 99. It has not been many years since writers on 
 agriculture affirmed that the inorganic constituents 
 of a good soil are inexhaustible. Such statements 
 are contrary to the teachings of science and of prac- 
 tical experience. It is true, the application of scien- 
 tific principles in farming will not in every case pro- 
 duce a good crop, because there are conditions that 
 human agency cannot control. The wind, and rain, 
 and sunshine are given or withheld by a power 
 which we cannot govern, and without whose favor- 
 ing influence all our labor is in vain. 
 
 100. Science not only determines the kind and 
 quality of food which plants need, but points out the 
 localities where this food can be obtained, and fur
 
 THE IMPROVEMENT OF SOILS. 
 
 47 
 
 nishes the farmer with methods for preparing, in con- 
 centrated form, the very elements which are deficient 
 in an unproductive soil. Through the influence 
 of its teachings, the manufacture of fertilizers has 
 become one of the great industries of the world. 
 Substances in the highest degree offensive, injuri- 
 ous to health, and difficult to be gotten rid of, 
 have been converted into merchandise of great 
 value. 
 
 101. The disposal of refuse matter, by putting it 
 to profitable use, is one of the greatest results ot 
 modern science. A portion at least of the sewage of 
 London, and other large cities of the world, is now 
 rendered harmless, and inoffensive, and even valua. 
 ble as an article of trade. A perfect system of agri- 
 culture requires that it should all be returned to the 
 soil whence it came, and serve as food for growing 
 crops. The indestructibility of matter, in connection 
 with the correlation and conservation of energy, pre- 
 sents nature as a grand system of mutually depen- 
 dent parts which move in a ceaseless round of univer- 
 sal harmony. It is for science to study the relation 
 of these parts, however vast or minute, and teach us 
 how to control their movements so as to promote 
 the interests of the human race. Much has been 
 done in this direction, while much remains to be 
 accomplished. 
 
 102. All truly scientific methods of improvement 
 of soils are founded on observation and experiment 
 and are addressed to the reason and common sense
 
 4 8 SCIENTIFIC AGRICULTURE. 
 
 of intelligent men. If a soil has all the constituents 
 that plants need, and in the best possible condition 
 for use as plant-food, then such soil cannot be im- 
 proved. If, however, one or more constituents are 
 deficient, or entirely absent, or not in the best con- 
 dition to serve as plant-food, then improvement is 
 not only possible, but desirable. 
 
 103. The means used for the improvement of 
 soils are : 
 
 Mechanical, as draining, plowing, sub-soiling, 
 mixing with clay, etc. 
 
 Chemical, as manuring or fertilizing. 
 
 The first changes the physical properties; the 
 second, the composition. When necessary constitu- 
 ents are absent or deficient, no amount of draining 
 or sub-soiling will secure a good crop. 
 
 104. The extensive and thorough system of drain- 
 ing by means of tiles or clay pipes, which is used 
 in Europe and in some portions of our own country, 
 is too costly where land is cheap and abundant. In 
 such cases open ditches should be used to carry off 
 surplus water. Intelligent farmers understand very 
 well the importance of removing excess of water by 
 some sort of drainage that will be least likely to re- 
 move the soil with it, but unfortunately they do not 
 always put their knowledge into practice. Where 
 loose rock is convenient, covered ditches with ten or 
 twelve inches of rock at the bottom are easily made, 
 and form excellent drains. Deep plowing and sub- 
 soiling are means of draining, to a limited extent,
 
 THE IMPROVEMENT OF SOILS. 4Q 
 
 but cannot be substituted for ditching in wet, swampy 
 lands. 
 
 105. The advantages of drainage are numerous, 
 of which may be mentioned the following: 
 
 (i.) It makes the soil warmer. The evaporation 
 of water from any surface is cooling. The heat of 
 the sun falling on a wet soil is taken up in convert- 
 ing the water into vapor, and does not reach the roots 
 of the plant. 
 
 (2.) It keeps the plant food from becoming too 
 much diluted, and leaves it in a concentrated form 
 for absorption by the plant. 
 
 (3.) It gives free access of air to the roots of 
 plants. Water not only keeps out the air, but 
 drowns or destroys the soil roots. 
 
 (4.) It aids in bringing about a proper decompo- 
 sition of organic matter, and preventing the forma- 
 tion of organic acids that are hurtful. Swampy lands 
 which are generally sour and unproductive for valu- 
 able crops are rendered productive by draining. 
 
 106. Deep plowing and sub-soiling not only as- 
 sist in draining the soil, but also render it better able 
 to stand a drought. The surplus water of heavy rains 
 can sink down without washing, while the capillary 
 action of a thoroughly pulverized soil draws mois- 
 ture from a greater depth in time of drought, and the 
 roots penetrate more easily beyond the influence of 
 the sun's rays and find abundant food, while air can 
 also reach a lower depth more readily and exercise 
 its disintegrating effect. 
 
 4
 
 5 
 
 SCIENTIFIC A GRICUL TURE. 
 
 107. Deep plowing also brings new earth to the 
 surface, and forms a deeper soil, altering its physical 
 and chemical properties and promoting the growth 
 of vegetation. Should the sub-soil be less fertile 
 than the surface, which is generally the case, care 
 should be taken not to bring much of it to the sur- 
 face during any one season. After the soil has been 
 deepened sufficiently, the sub-soil should only be 
 stirred by means of the sub-soil plow. 
 
 108. A very economical and effective method of 
 sub-soiling is to run a plow with a long narrow shovel 
 immediately behind the common turn-plow. The 
 shovel can be made by a common blacksmith, and 
 be easily repaired. The expense of sub-soiling can 
 thus be made very light, while the advantages, espe- 
 cially in heavy soils, are sure to be recognized after 
 a thorough trial. 
 
 109. There are other mechanical means of im- 
 provement, such as the mixing of stiff clays with 
 light, sandy soils, and the opposite, which are prac- 
 tised with advantage in thickly populated countries, 
 but which cannot be profitably employed by us in 
 the cultivation of wheat, com, cotton, and tobacco. 
 The main object is to secure the greatest amount 
 of improvement at the least expense. An unset- 
 tled feeling frequently prevails among farmers and 
 planters in a new country which operates strongly 
 against anything like permanent improvement, and 
 tends to produce careless cultivation and rapid ex- 
 haustion of the soil. The abundant supply of new
 
 THE USE OF MANURES. 
 
 5 1 
 
 lands in the far West tends to produce the same re- 
 sult. 
 
 no. It is a narrow-sighted policy that opposes 
 thorough cultivation and the use of fertilizers, on 
 the ground that this may be the last crop, and such 
 investments of labor and capital can not be remu- 
 nerative the first year. Thorough, cultivation is 
 always proper. Whether fertilizers should be used, 
 as well as what kinds, depends upon circumstances, 
 which will be discussed in the next chapter. 
 
 CHAPTER VII. 
 
 THE USE OF MANURES, OR FERTILIZERS. 
 
 in. THE chemical improvement of soils em- 
 braces the use of fertilizers, or manures, the applica- 
 tion of which depends on the following well-estab- 
 lished principles : 
 
 1. Plants derive an essential part of their food 
 from the soil. This includes all the inorganic ele- 
 ments found in the ash, and a variable quantity of 
 those organic elements which volatilize when the 
 plant is burned. 
 
 2. Different plants require a special supply of 
 different kinds of inorganic food, or the same kinds 
 in different proportions, which must be contained in 
 the soil. 
 
 3. Some soils have a deficiency of plant-food
 
 5 2 SCIENTIFIC AGRICULTURE. 
 
 which must be supplied before particular plants can 
 grow. The food may be in the soil, but not in a 
 condition to be appropriated by the plant. 
 
 112. Soils may be naturally deficient in impor- 
 tant constituents, or they may have become so by 
 long-continued cultivation and removal of crops. 
 In such cases, improvement is effected by the addi- 
 tion of a suitable fertilizer, or manure. 
 
 113. The continued removal of crops is sure to 
 produce exhaustion. The following table. shows the 
 quantity and composition of the ash contained in 
 one English ton (2,240 pounds) of hay of different 
 kinds, and which is carried off when the hay is taken 
 from the farm (the numbers represent pounds) : 
 
 
 Italian ry- 
 graishay. 
 
 Clover ha;. 
 
 Lucerne hay. 
 
 Rod. 
 
 White. 
 
 Potash 
 
 17 
 
 13?* 
 3 
 
 j* 
 
 8iK 
 
 26 
 
 s 
 
 55^ 
 i7K 
 
 18 
 
 6% 
 10 
 
 4 
 5 
 
 2*X 
 
 10^ 
 
 45^ 
 \ 
 
 12^ 
 2O 
 
 6 
 
 3 ,/ 
 13^ 
 10754 
 
 '! 
 
 9 
 29 
 
 6% 
 
 7% 
 
 Soda . . . 
 
 Lime 
 
 
 
 
 Phosphoric acid 
 
 
 Silica 
 
 
 138 
 
 *9% 
 
 H'K 
 
 2M 
 
 114. Animal products also remove valuable con- 
 stituents, and in large quantities, as can be seen from 
 the following table, which is based upon the experi- 
 ence of Messrs. Lawes and Gilbert, two noted Eng- 
 lish agriculturists :
 
 THE USE OF MANURES. 
 
 S3 
 
 Composition of Animal Exports from a Farm. 
 
 
 Nitrogen. 
 
 Phosphoric 
 acid. 
 
 Potash. 
 
 Lime. 
 
 Magne- 
 sia. 
 
 Fat ox, per 1,000 Ibs. fasted | 
 
 Lbs. 
 
 23.18 
 
 LU. 
 16.52 
 
 Ll.i. 
 1.84 
 
 Lbs. 
 19.20 
 
 Lbi. 
 0.63 
 
 Fat sheep, per 1,000 Ibs. fast- (^ 
 
 19.60 
 
 11.29 
 
 1-59 
 
 12. 80 
 
 o-53 
 
 Fat pig, per 1,000 Ibs. fasted 1 
 
 17-57 
 
 6.92 
 
 1.48 
 
 6.6 7 
 
 o-3S 
 
 
 
 
 i. 80 
 
 1.56 
 
 
 Wool, unwashed, 1,000 Ibs 
 
 73.00 
 
 1. 00 
 
 40.00 
 
 I.OO 
 
 O.7O 
 
 By " fasted " is meant that the animals were killed 
 when their digestive organs were empty, or nearly 
 so. 
 
 115. The rapidity of exhaustion will depend upon 
 the kind of products removed. Some writers assert 
 that the amount of plant-food in good soils is so 
 great, that practically they can not be exhausted, but 
 the experience of farmers proves the contrary. Good 
 crops of wheat have been grown on the same soil for 
 a number of years without manures, but careful ex- 
 periments show that there is a gradual falling off in 
 the yield. 
 
 1 1 6. The fertilizers, or manures used for improv- 
 ing soils and restoring fertility, may be divided into 
 three kinds, vegetable, animal, and mineral. 
 
 117. As every decaying plant contains all the 
 constituents necessary for the growth of a similar 
 plant, of course it furnishes a good fertilizer. Vege- 
 table substances, such as clover, pea-vines, etc., are 
 sometimes plowed in with great benefit to the soil. 
 They not only furnish material properly prepared as
 
 54 
 
 SCIENTIFIC AGRICULTURE. 
 
 available food, both organic and inorganic, but they 
 are also highly useful in making stiff lands mellow 
 and porous, and light soils retentive of moisture. 
 
 118. Cornstalks laid in a furrow and the earth 
 bedded upon them, and even weeds when turned 
 under, produce a. fine mechanical effect on stiff lands 
 apart from their value as chemical manures. Whether 
 green or dry, these vegetable substances soon under- 
 go decomposition, and give up their constituents as 
 food to growing plants. 
 
 119. Cotton-seed is one of the best and most ener- 
 getic of this class of fertilizers. It contains a great 
 deal of nitrogen, which has a wonderful effect in stim- 
 ulating vegetable growth. Leaves, and all sorts of 
 vegetable matter, can be profitably used, which, as a 
 top-dressing, produce warmth, and as they decay 
 furnish valuable plant-food. 
 
 120. The large amount of cotton-seed produced 
 in the South has caused special attention to be called 
 of late years to its value and to the best method of 
 using it as a fertilizer. Like other seeds it is rich 
 in potash and phosphoric acid, two important con- 
 stituents of a fertile soil, which are generally in such 
 limited quantities that in the process of removal of 
 crops they are the first to become deficient. Cotton 
 lint contains only about i per cent, of ash or mineral 
 matter, while the seed contains about 9 per cent. In 
 a bale of cotton, the yield of say 1,700 pounds of seed- 
 cotton, we have only five pounds of mineral matter 
 in the lint, and one hundred and eight in the seed
 
 THE USE OF MANURES. 
 
 55 
 
 The removal of the seed, therefore, is more than 
 twenty-one times as exhaustive of mineral matter as 
 the removal of the lint. 
 
 121. If the seed be returned to the soil, there is 
 no marketable crop less exhaustive of mineral mat- 
 ter than cotton, but if the seed be permanently re- 
 moved the result is quite different. In view of the 
 importance of restoring this valuable substance to the 
 soil, the question arises, How can it be done with the 
 greatest advantage to succeeding crops? Like all 
 organic substances it must undergo decomposition 
 before it can serve as plant-food. If this decom- 
 position be effected in a heap without mixing with 
 earthy matter, the ammonia generated will mostly 
 escape. This escaping ammonia is the most ener- 
 getic stimulant known, and should, by all means, be 
 preserved. 
 
 122. An economical mode of application is to 
 grind or crush the seed, scatter it in deep furrows, 
 and cover it up some time before planting. The 
 practice of scattering the seed in the drill at the time 
 of planting does very well, provided too large a quan- 
 tity is not used. The decay of cotton-seed is a spe- 
 cies of combustion, or fermentation which generates 
 considerable heat, and if the roots of the young cot- 
 ton-plant are in contact with the hot, fermenting 
 mass, they are almost sure to be destroyed. If, how- 
 ever, the fermentation takes place below the plant, 
 with a layer of earth between, the young plant will 
 be stimulated and nourished by the escaping vol-
 
 5 6 SCIENTIFIC AGRICULTURE. 
 
 atile products of decomposition, and the roots thus 
 strengthened will reach down, and appropriate the 
 food contained in the decaying seed. 
 
 123. To those living near an oil-mill, there will 
 be great economy in having the oil first extracted 
 from the seed, and then using the oil-cake as a fertil- 
 izer. The oil is a product of great value for certain 
 purposes, but of little value as a manure, because it 
 contains only the organic elements, carbon, hydro- 
 gen, and oxygen, which are supplied by the atmos- 
 phere to every plant. 
 
 124. The process of grinding or crushing the 
 seed promotes decomposition, and hastens its avail- 
 ability as plant-food ; but the expense of the neces- 
 sary machinery is too great for general use, unless 
 the kernel is to be used as food for stock, for which 
 purpose it is admirably suited. The valuable pro- 
 ducts of decomposing cotton-seed may be preserved 
 by composting, or mixing with other fertilizers which 
 can absorb or combine with its volatile products. 
 
 125. The important object to be accomplished, 
 on every farm or plantation, is the restoration to the 
 soil, in some form or other, of the large amount of 
 valuable mineral matter contained in the seed, and 
 the prevention of its permanent removal to the grad- 
 ual exhaustion of the land. In Europe, rape-seed 
 and linseed-cake, similar to our cotton-seed oil-cake, 
 are highly esteemed as fertilizers. 
 
 126. Animal fertilizers, consisting of the flesh of 
 all dead animals, with the scrapings of tanneries and
 
 THE USE OF MANURES. 
 
 57 
 
 the offal of slaughter-houses, are among the most 
 stimulating substances used to promote the growth 
 of vegetation. The animal structure contains every 
 element of the plant except silicon, and some por- 
 tions of the body contain most valuable constituents 
 in a highly concentrated form. The products of 
 decomposition are especially rich in nitrogen. 
 
 127. The bones and excrements of animals, 
 among the most powerful and valuable of fertilizers, 
 generally undergo some manipulation, or preparation 
 before being used, which renders them more suit- 
 able for immediate use, or more convenient for 
 handling. 
 
 128. Raw bones when dried consist chiefly of 
 tricalcium phosphate (common phosphate of lime) 
 and gelatinous matter, in the proportion of about 
 two-thirds of the former to one-third of the latter. 
 Their average composition may be stated as follows : 
 
 Per cent. 
 
 Animal matter 33 
 
 Tricalcium phosphate , 57 
 
 Calcium carbonate 8 
 
 Calcium fluoride I 
 
 Magnesium phosphate I 
 
 129. Bones are sometimes merely ground to a 
 fine powder, and sown broadcast, or drilled with the 
 grain at the time of planting. In this case their ac- 
 tion is slow, because they are insoluble in water, and
 
 5 8 SCIENTIFIC AGRICULTURE. 
 
 their constituents must be rendered soluble before 
 they can be taken up by the plant and used as food. 
 This change will take place gradually in the soil. 
 
 130. In order to hasten the action of bones, it is 
 customary to convert them into what is known as 
 superphosphate. This is done by mixing .the 
 broken or ground bones with about half their weight 
 of common sulphuric acid, or oil of vitriol diluted 
 with two or three times its weight of water. After 
 the acid has acted upon the bones, a somewhat pasty 
 mass is formed, which may be mixed with ashes, saw- 
 dust, rich earth, refuse of salt-refineries, etc., to neu- 
 tralize excess of acid. 
 
 131. The insoluble bone, or calcium phosphate, 
 is thus changed by the acid into a soluble phosphate, 
 commonly known as superphosphate. The sul- 
 phuric acid removes a portion of the calcium from 
 the bones forming calcium sulphate, or gypsum, 
 which is itself an excellent fertilizer. The addition 
 of ashes to neutralize excess of acid is an advantage 
 to the mixture, but unfortunately manufacturers or 
 dealers sometimes add sand and earth of no value, 
 in such quantities that suspicion has been cast upon 
 the genuineness of much of our commercial super- 
 phosphate. 
 
 132. A large deposit of tricalcium, or bone phos- 
 phate, the remains of extinct animals, was discovered 
 near Charleston, South Carolina, some years ago. It 
 furnishes an abundant supply of this material, and 
 has caused a reduction in the cost of superphos-
 
 THE USE OF MANURES. 
 
 59 
 
 phates. An analysis of South Carolina phosphate 
 shows it to contain 
 
 Per cent. 
 
 Moisture 7.79 
 
 Organic matter and water of combination 4.60 
 
 Silica 10.35 
 
 Calcium carbonate 8.20 
 
 Tricalcium phosphate 61.89 
 
 Earthy and alkaline salts 7.17 
 
 Total 100.00 
 
 133. Hundreds of tons of cattle and buffalo bones 
 are brought from the Western Plains, and are either 
 used in the form of ground bones, or first converted 
 into superphosphate. The following mean of many 
 analyses of superphosphates, taken from " Phosphates 
 of Commerce," by Jones, will show their general 
 composition : 
 
 Per cent. 
 
 Moisture I4-5O 
 
 Organic and volatile matter 12.91 
 
 Monocalcium phosphate, or superphosphate *. . 17.30 
 
 Tricalcium, or bone phosphate 4.16 
 
 Calcium sulphate 47-78 
 
 Alkaline salts 0.15 
 
 Sand 3.20 
 
 Total loo.oo 
 
 * Equal to 27.08 per cent, of bone phosphate rendered sol- 
 able. " Monocalcium phosphate," in the above statement, is 
 sometimes called " biphosphate of lime." It is, according to 
 the modern chemical nomenclature, tetrahydrogen calcium di 
 phosphate.
 
 60 SCIENTIFIC AGRICULTURE. 
 
 134. The manufacture of superphosphates is per- 
 haps too difficult for the ordinary farmer, and yet 
 in some cases it can be made profitable. To any 
 one disposed to try the experiment, the following 
 directions are given, which, if strictly followed, will 
 insure a good result : 
 
 Secure a carboy of sulphuric acid, commonly 
 known as " oil of vitriol," break up the bones as fine 
 as possible, and to one hundred pounds of bones 
 add forty pounds of acid, previously mixed with 
 twice its bulk of water, and cooled. The mixing of 
 the acid and water together produces great heat. 
 It is best to pour the acid into the water with con- 
 stant stirring. After the mass has become pasty by 
 solution of the bones, add ashes, mix thoroughly, 
 and allow the mass to dry. It can easily be re- 
 duced to a powder, and thus applied to the soil. A 
 long trough or one or more barrels may be used in 
 making the solution, or the finely broken bones may 
 be placed in a pile on a suitable floor, and sprinkled 
 from time to time with diluted acid. The acid must 
 be handled with care, as it is highly corrosive. From 
 two to three hundred pounds of this mixture should 
 be used per acre. 
 
 135. Dr. Nichols, in his " barn-floor lecture,' 5 
 gives the following practical directions for making 
 superphosphate from charred bones, a substance 
 used by sugar-refiners for decolorizing syrups, and 
 then sold to makers of fertilizers : 
 
 " A box four feet square and one foot deep is
 
 THE USE OF MANURES. 6 1 
 
 lined with thick sheet-lead the lead in one piece, 
 soldered at the corners strongly with lead solder. 
 Its capacity is just right for making one-fourth of a 
 ton of superphosphate at a time, and it requires a 
 whole carboy of vitriol, so that no fractional parts 
 of acid are left to cause trouble. It requires : 
 
 One carboy of oil of vitriol 165 pounds 
 
 Bone-charcoal 380 " 
 
 Water 10 gallons 
 
 " The water is first placed in the trough, and the 
 acid is added to it gradually, causing a great boiling, 
 with evolution of heat and steam. It takes about an 
 hour for the reaction to become complete, and then 
 it will soon dry and be free from moisture. It needs 
 no grinding, it is ready for the field as soon as 
 cool." 
 
 136. Guano, one of the most costly and valuable 
 of fertilizers, was in use by the inhabitants of South 
 America, when the Spaniards under Pizarro overran 
 and subdued the powerful empire of the Incas. Pres- 
 cott, in his history of " The Conquest of Peru," gives 
 an interesting account of the progress made in agri- 
 culture by the aborigines of that country. In some 
 places where the dry sandy plains were unproduc- 
 tive, they sank immense pits, some of which were an 
 acre or more in extent, and dug out to a depth of 
 fifteen or twenty feet, in order that moisture suffi- 
 cient for vegetation might be afforded. Other con- 
 ditions of fertility were supplied by thorough pul-
 
 62 SCIENTIFIC AGRICULTURE. 
 
 verization of the soil and a systematic application of 
 fertilizers. 
 
 137. The fertilizer in common use among the Pe- 
 ruvians was guano, the excrement of immense flocks 
 of sea-birds which frequent the rocky islands near the 
 coast. Countless numbers of birds have for centu- 
 ries hatched and reared their young on these islands, 
 leaving deposits which cover a large extent of sur- 
 face, and are in places from twenty to fifty feet in 
 thickness. It was estimated, thirty years ago, that 
 on the Chincha group of islands there were from 
 twenty to twenty-five millions of tons. It has been 
 so long accumulating that in some localities the de- 
 posit is found in layers with sand like a regular geo- 
 logical formation. 
 
 138. The importance of this fertilizer was so 
 highly appreciated by the old Peruvians that, when 
 the Spaniards first visited the country, special laws 
 were in operation to regulate its use, and enforce its 
 application to the soil by those engaged in agricul- 
 ture. Its value was not known or appreciated in 
 Europe or in our own country until within the last 
 thirty or forty years. The credit of introducing it 
 into Europe is ascribed to Humboldt. The first 
 cargo was taken to England in 1826, but its value 
 was not understood until a number of years after- 
 ward. 
 
 139. Liebig, in his " Letters on Modern Agricul- 
 ture," says: "Before 1840, guano had never been 
 used as a manure on a European field. When the first
 
 THE USE OF MANURES. 63 
 
 vessel loaded with guano arrived at Liverpool, nu- 
 merous experiments were made with the new manure 
 which proved failures, and agriculturists were not 
 agreed about its utility until they had practically 
 tested its use. Since that time, many hundreds of 
 ships have passed to and fro, and have brought to 
 the European Continent guano to the value of about 
 300,000,000 florins (about $125,000,000) ; and, within 
 the same period, there has been produced a surplus 
 of more than 400,000,000 cwt. of corn, or of its equiv- 
 alent in flesh. It is true, guano would have found 
 its way to Europe even without the recommenda- 
 tion of science, but it would not have made its 
 way so speedily. In the late period of sterility 
 through which we have passed, it has been the 
 means of alleviating the wants of many millions 
 of men." 
 
 140. The first shipment of guano to the United 
 States was made in 1845, and up to June 30, 1855, 
 about half a million tons had been imported, while 
 the amount sent to Europe during the same period 
 was vastly greater. The Government of Peru has 
 derived a large revenue from the sale of this valuable 
 fertilizer, and the ships of all nations have engaged 
 so actively in the trade that the supply on the isl- 
 ands has greatly diminished. The ocean has been 
 searched for other islands containing similar de- 
 posits, and, while some have been found, none are 
 esteemed so highly as those on the coast of South 
 America.
 
 64 SCIENTIFIC AGRICULTURE. 
 
 141. .On these Peruvian islands it seldom or never 
 rains, while the hot sun rapidly evaporates the mois- 
 ture naturally contained in the deposit, and leaves 
 the valuable constituents in their most concentrated 
 form. On other islands frequented by sea-birds, a 
 great deal of that which is valuable in the deposits is 
 washed out by rains more or less frequent. Guano 
 has been brought from a few islands on the coast of 
 Africa and other parts of the world where rain sel- 
 dom falls, but none has been found equal in value to 
 the Peruvian. 
 
 142. The guano-producing birds feed on fish, a 
 food especially rich in phosphates and nitrogenous 
 compounds. The mixture of their solid and liquid 
 excrements contains in a highly concentrated form 
 those very elements which are most likely to be 
 deficient in soils, and hence its universal applica- 
 bility. 
 
 143. The composition of guano varies consider- 
 ably in different samples. An average analysis of 
 Peruvian guano imported into Ireland in 1876 is 
 given by Johnston and Cameron as follows : 
 
 Per cent. 
 
 Moisture 13.13 
 
 Organic matter, etc.* 48.17 
 
 Calcium phosphate 26.58 
 
 Alkaline salts i i.oo 
 
 Insoluble matter - 1.12 
 
 100.00 
 
 * Yielding ammonia II. 80.
 
 THE USE OF MANURES. 65 
 
 144. Peruvian guano contains less moisture than 
 African and Patagonian because the climate of Peru 
 is drier. It also has a less pungent smell of ammonia. 
 As guano is often adulterated with sand, earth, etc., 
 the following physical properties and tests will en- 
 able one who is not a chemist to distinguish between 
 a good guano and one of inferior quality, or one 
 which has been adulterated. 
 
 145. Genuine guano is a substance of a yellow- 
 ish-brown color, of a peculiar urinous odor, and 
 has mixed with it, white lumps or fragments. When 
 heated on a shovel or iron plate, at least half of it 
 will volatilize, and nearly the whole of the remain- 
 der will dissolve in dilute hydrochloric acid. Sand 
 and earthy adulterations will be left undissolved, which 
 in good guano does not amount to more than from 
 i to 2 per cent. When first heated, it gives off 
 white vapors with a strong smell of ammonia. This 
 odor is greatly increased by the addition of lime. 
 The ash should be white or grayish ; a yellow or 
 red ash indicates an admixture of clay or earthy 
 matter. 
 
 146. The highly stimulating effect of guano is due 
 to the large amount of nitrogenous matter which 
 it contains. The atmosphere furnishes nitrogen to 
 plants in the form of ammonia, but not in sufficient 
 quantity to meet the demands of a luxuriant growth 
 of wheat, corn, or other crop. This must be sup- 
 plied by decaying nitrogenous matter, salts of am- 
 monia, or nitrates.
 
 66 SCIENTIFIC AGRICULTURE. 
 
 147. The newly sprouted plant stands ready to 
 grow, it may be with all its organs perfect, and with 
 every article of food at hand, but, so long as there is . 
 only a limited supply of one important element, the 
 rapidity and vigor of its growth will be retarded. The 
 air contains an abundant supply of nitrogen, but not 
 one atom of it, as chemists believe, is contributed 
 directly to the growth of plants. This important 
 element, before it can be used as plant-food, must be 
 in union with some other element, and guano furnish- 
 es it in the best possible combination. The phos- 
 phates, too, which exist so largely in guano and other 
 salts, give additional value to this fertilizer. 
 
 148. Guano, then, as we have shown, promotes 
 the growth of vegetation by furnishing a large supply 
 of nitrogen in an available form, and a few other 
 highly important constituents of our most valuable 
 crops. As it does not contain all the elements of 
 plant-food, there may be soils which it will not great- 
 ly benefit unless mixed with other substances. It is 
 well to keep in mind the fact that all the elements 
 of plants are necessary for growth. The reports of 
 failure in the use of guano and other fertilizers, and 
 statements to the effect that they " run out " and, in 
 the end, "make the soil poorer," may be explained 
 by the fact that such manures lack some elements 
 which every fertile soil must contain ; or they may 
 so stimulate a comparatively poor soil that in a few 
 years the supply of some important element which 
 the jnino or other manure lacks will be exhausted.
 
 Tff USE OF MANURES. 67 
 
 Of course, a further application of guano without 
 the addition of this deficient element will prove a 
 failure. The fault- is not in the fertilizer, but in not 
 supplying other material. 
 
 149. It is customary to mix guano with other fer- 
 tilizers not so rich in ammonia, and thus have a ma- 
 nure that can be used profitably for almost any crop. 
 A large number of " manipulated guanos " are sold, 
 and where the manipulation, or mixing with other fer- 
 tilizers, has been fairly and honestly done, such mix- 
 tures are highly beneficial and economical. 
 
 150. Peruvian guano and other strongly nitro- 
 genous manures should never be placed in imme- 
 diate contact with the seed, because the ammonia 
 given off is very caustic, and will kill the seed-germ. 
 It may be placed under the seed with a few inches 
 of earth between, or at the side, the former being 
 preferable. 
 
 151. A mixture of one hundred pounds of Peru- 
 vian guano with two hundred of a good superphos- 
 phate per acre gives excellent results. The ingre- 
 dients should be thoroughly mixed, sown broadcast, 
 and turned in with the wheat or other grain, or they 
 may be placed under the bed on which cotton or 
 corn is to be planted. In wheat-growing States, 
 drills are used both for planting the wheat and for 
 depositing the guano and superphosphate. Some 
 farmers prefer scattering the fertilizer broadcast, 
 whether for cotton, wheat, or other crop. 
 
 152. It will not do to mix guano with fresh ashes
 
 68 SCIENTIFIC AGRICULTURE. 
 
 or lime, because the potash contained in ashes, as 
 well as lime, sets free the ammonia. This ammonia, 
 in all ammoniacal fertilizers, is either free or in com- 
 bination with acids. Potash, soda, and lime have 
 a stronger affinity for these acids than the ammonia, 
 and hence they take its place. The ammonia being 
 a gas, passes off and diffuses itself in the air. It is 
 important to understand the chemical principles in- 
 volved in mixing fertilizers, as well as in their action 
 when applied to the soil. 
 
 153. Stable or farm-yard manure is the most 
 common of fertilizers, and one which every farmer 
 and planter can have in great abundance without 
 much trouble or outlay of money. It only requires 
 the exercise of a little care in its preservation in or- 
 der to secure a large supply on every farm. Stable- 
 manure consists of the solid and liquid excrements 
 of animals which feed on some of our most valuable 
 crops, mixed with portions of these crops in a more 
 or less advanced stage of decomposition. It consti- 
 tutes a stimulating and nutritive fertilizer applicable 
 to all crops. 
 
 154. The value of stable-manure depends to some 
 extent on the food of the animal ; the richer the food, 
 the better the manure. The liquid portion is espe- 
 cially rich in phosphates and compounds of nitrogen, 
 and should never be allowed to run to waste. When- 
 ever a manure-heap gives out a strong smell, some 
 of its valuable constituents are escaping. In such 
 cases, the smell of ammonia may not be perceptible,
 
 THE USE OF MANURES. 69 
 
 but its escape can easily be determined by the com- 
 mon test for this substance, that is, the formation of 
 a white vapor with hydrochloric acid. A glass rod 
 dipped into this acid, and brought in contact with 
 the gaseous ammonia, will show the effect mentioned. 
 To prevent the escape of ammonia, the heap as it 
 accumulates should be covered or mixed with earth, 
 or sprinkled occasionally with dilute hydrochloric, 
 or sulphuric acid, or solution of ferrous sulphate, 
 known as copperas. Lime and ashes must not be 
 added, because they would release the ammonia, in- 
 stead of retaining it. 
 
 155. Manure-heaps should be kept moist in order 
 that fermentation or decomposition may go on, but 
 should not be exposed to violent rains which wash 
 out soluble ingredients of great value. Perhaps the 
 best and most economical plan for general use, is to 
 pile the manure carefully in rail pens and cover 
 lightly with boards, and, even if not covered, the 
 pens will prevent the scattering and wasting of the 
 manure. The excrements of all our domestic ani- 
 mals should be added to these piles, together with 
 the sweepings of yards, and refuse of all kinds. By 
 this means, with a little attention and no outlay of 
 money, much valuable material which is now lost 
 could be restored to the soil. 
 
 156. Human excrements, so abundant in large 
 cities, form a manure of considerable value. When 
 dried, powdered, and mixed with charcoal, gypsum, 
 etc., it is sold under the name of poudrette. Large
 
 7 o SCIENTIFIC AGRICULTURE. 
 
 quantities are prepared in Europe which command 
 a good price, but in this country it is used to a 
 very limited extent. The efforts thus far made 
 to utilize the sewage of cities have in some in- 
 stances proved successful, but there are difficulties 
 yet to be removed before its profitable use can 
 become general. 
 
 157. Animal manures are richer than vegetable 
 because they contain more nitrogen, which in the 
 process of fermentation and decay unites with hy- 
 drogen to form ammonia, and because they also con- 
 tain a larger proportion of valuable inorganic ele- 
 ments. The effect of respiration and digestion, the 
 two great vital functions of the animal system, is to 
 extract carbon and hydrogen from the food through 
 the blood and lungs where they escape as carbon 
 dioxide and water. The water in large quantities 
 passes through the pores of the skin, leaving the 
 other constituents in a more concentrated form. 
 
 CHAPTER VIII. 
 
 MINERAL FERTILIZERS. 
 
 158. THE list of mineral fertilizers embraces 
 a large number of substances, only a few of which, 
 however, will be mentioned, such as lime, marl, gyp- 
 sum, salt, and ashes.
 
 MINERAL FERTILIZERS. y t 
 
 159. Lime, or calcium oxide, is made by heating 
 common limestone in a suitable kiln. This mineral, 
 when pure, consists of lime in combination with car- 
 bon dioxide, or carbonic-acid gas. The rock is bro- 
 ken into small-sized pieces, placed loosely in what 
 is known as a kiln, and, by means of wood or coal, 
 thoroughly heated until the carbon dioxide is driven 
 off. Calcium oxide, or quicklime, is left. One hun- 
 dred pounds of pure limestone yield fifty-six pounds 
 of lime. 
 
 1 60. If water be poured on quicklime, a portion 
 of the water will combine with it, giving out heat, 
 and forming slaked lime. The same result will be 
 produced by exposing the quicklime to moist air. 
 Long exposure to air will result in a reunion of car- 
 bon dioxide with the lime. The new carbonate 
 will be in a finely divided condition, which is better 
 for fertilizing purposes than the original limestone, 
 though not so good as the slaked lime (30). 
 
 161. One hundred pounds of quicklime (also 
 called caustic lime) unite with thirty-two pounds of 
 water in the process of slaking. This water is not 
 mixed with the lime, but forms a chemical compound 
 known as calcium hydroxide. This hydroxide is 
 slighty soluble in water, of caustic taste, and when 
 mixed with sand forms common mortar. The hard- 
 ening of mortar is due to the absorption of carbon 
 dioxide from the air, and a gradual union of the lime 
 with the silica, or sand. 
 
 162. The application of lime to soils furnishes at
 
 7 2 SCIENTIFIC AGRICULTURE. 
 
 least one mineral constituent to plants, one, however, 
 that generally exists in soils, and hence its valuable 
 and often surprising effects are not to be attributed 
 to the plant-food it contains so much as to other im- 
 portant purposes which it serves. Its alkaline prop- 
 erties cause it to neutralize acids, which sometimes 
 exist injuriously in soils. It also renders stiff clays 
 light and mellow, and aids in the decomposition of 
 organic substances, and of some insoluble inorganic 
 compounds. In other words, lime corrects " sour- 
 ness " in lands, destroys excess of vegetable matter, 
 lightens heavy clay soils, and releases potash for the 
 use of plants by decomposing silicates. 
 
 163. Marl is a mixture of calcium carbonate 
 derived chiefly from the shells of animals clay and 
 sand in variable proportions. It is generally valued 
 according to the amount of calcium carbonate it con- 
 tains, which may vary from five to ninety per cent., 
 though in almost all marls there are other valuable 
 constituents. The calcium carbonate, or carbonate 
 of lime, as it is generally called, is usually in a finely 
 divided state, and can be readily used as food by the 
 plant. 
 
 164. The celebrated New Jersey green-sand marl 
 contains a large percentage of potash, which gives it 
 great value. Excellent marls are found in many 
 parts of the country, and need no preparation before 
 using. The following analysis by Professor Norton 
 will give some idea of the composition of an excel- 
 lent marl
 
 MINERAL FERTILIZERS. 
 
 Per cent. 
 
 Calcium oxide (lime) 35-OO 
 
 Carbon dioxide 45-O2 
 
 Oxide of iron and aluminium, \ , 
 
 with traces of phosphoric acid f 
 
 Magnesium oxide 0.66 
 
 Organic matter 7.06 
 
 Sand 9.57 
 
 73 
 
 165. Some marls consist almost entirely of shells 
 more or less broken ; in others, clay or sand predom- 
 inates. Good marl always gives off a large quantity 
 of carbon dioxide on the addition of a strong acid, 
 and in this way some estimate may be formed of its 
 value (31). This fertilizer is particularly well suited 
 for application to sandy lands, supplying the very 
 elements which such lands generally need for the 
 continued production of good wheat and cotton 
 crops. 
 
 166. Gypsum, or calcium sulphate, also called land 
 plaster, is a very important mineral fertilizer and has 
 long been in use as a valuble manure for corn, tobacco, 
 wheat, clover, and the grasses generally. It is com- 
 posed of lime and an oxide of sulphur in chemical 
 combination with a large percentage of water. This 
 water can be driven off by heat leaving a white sub- 
 stance which, ground to powder, forms what is 
 known as plaster of Paris. In this form, it has the 
 property of recombining chemically with water and 
 forming a substance of the same composition as the
 
 74 SCIENTIFIC AGRICULTURE. 
 
 original gypsum. This property fits it admirably 
 for taking casts of statuary, for forming the " hard 
 finish " on the plastered walls of our houses, and for 
 stucco-work of all kinds. Dentists use it in large 
 quantities for taking casts of the mouth, and for 
 other purposes in their work, while it is useful to 
 artists in forming models from which to copy and 
 perfect the creations of their genius (32). 
 
 167. Gypsum is found in nature as a mineral, 
 generally as a white compact mass, though sometimes 
 in a transparent crystalline condition, as in the min- 
 eral selenite. Alabaster is also a form in which this 
 mineral is found, and used in the manufacture of 
 vases and other ornamental work. The rock is quite 
 soft, easily scratched with a knife, and whitens on 
 being heated. It contains about twenty-one per 
 cent, of water. As a fertilizer, it furnishes lime and 
 sulphur to plants, and is thought to have the power 
 of absorbing ammonia from the air and supplying it 
 to the plant. To this important property Liebig 
 ascribes much of its wonderful effect upon young 
 grass and wheat. It is usual to sow it broadcast 
 over wheat and grass during the early spring, and to 
 drop it with corn at the time of planting, or to drop 
 a small portion on each hill of corn after the corn 
 has been thinned. Corn moistened with water and 
 rolled in plaster at the time of planting, will get 
 a more vigorous start, and be the better enabled 
 to stand an early drought. Cotton-seed may also 
 be very advantageously rolled in plaster previous
 
 MINERAL FERTILIZERS. 
 
 75 
 
 to planting. For this purpose, the seed is placed 
 in a tub of convenient size, thoroughly moistened 
 with water, the plaster added, and the whole well 
 stirred. As much as will adhere is dropped with 
 the seed. 
 
 1 68. Gypsum, or plaster, has no caustic proper- 
 ties like quicklime and guano, and therefore seeds 
 are not injured by being placed in immediate contact 
 with it. The vigorous, healthy start which it gives 
 to the young plant is very desirable for both corn 
 and cotton, since weak, sickly plants are almost sure 
 to suffer from insects, or perish from other causes. 
 The noted English farmers, Lawes and Gilbert, found, 
 during four years, an average increase of nearly one 
 ton of hay per acre by the use of gypsum as compared 
 with adjoining land without gypsum. This is one of 
 the cheapest of fertilizers, and should be used by farm- 
 ers and planters who desire an increase of production 
 by a moderate outlay of money. It is not necessary 
 to mix gypsum with superphosphate, because, in the 
 process of making superphosphate from bones, cal- 
 cium sulphate, or gypsum, is always formed at the 
 same time, and constitutes a large part of the super- 
 phosphate. 
 
 169. Common salt has been used as a manure 
 from very ancient times. It can be used with ad- 
 vantage only in small quantities, as a heavy applica- 
 tion destroys vegetation. Common salt, or sodium 
 chloride, consists of two elements, chlorine and so- 
 dium, and is a valuable addition to compost-heaps.
 
 7 S SCIENTIFIC AGRICULTURE. 
 
 Its value as a manure is denied by some experiment- 
 ers. It acts, no doubt, in an indirect manner, releas- 
 ing nitrogen from some of its compounds and aiding 
 in the solution of calcium phosphate and other salts. 
 According to some writers, salt may be used to ad- 
 vantage for checking growth on lands which pro- 
 duce such an excess of straw as to cause wheat to 
 fall before the seed is matured. 
 
 170. In chemical language, salts are compounds 
 in which the hydrogen of an acid is replaced by a 
 metal. The union of a non-metallic element with a 
 metal forms a salt like sodium chloride. Another 
 class of salts have oxygen in them in addition to the 
 other non-metallic element, like potassium nitrate or 
 nitre, sodium nitrate or Chili saltpetre. These are 
 used as fertilizers, as are also sulphates of various 
 kinds, and the refuse salts from salt-works and 
 chemical manufactories. The utilization of what 
 were formerly waste products is carried to such 
 an extent in Europe that scarcely anything is lost. 
 Every product has a marketable value, and what 
 cannot be consumed by animals, or put to some 
 useful purpose, is returned to the soil as food for 
 plants. 
 
 171. Among mineral fertilizers may be classed 
 the ash of vegetable substances whether of wood, 
 coal, or plants. The following result of the analysis 
 of the ash of oak and beech wood shows the nature 
 of this fertilizer :
 
 MINERAL FERTILIZERS. 
 
 Percentage of Oak. Beech. 
 
 Potassium oxide 8.43 15.83 
 
 Sodium oxide 5.64 2.79 
 
 Sodium chloride . 0.02 0.23 
 
 Calcium oxide, or lime 74-63 62.37 
 
 Calcium sulphate 1.98 2.31 
 
 Magnesium oxide, or magnesia 4.49 11.29 
 
 Iron oxide, or ferric oxide 0.57 0.79 
 
 Phosphoric pentoxide or phosphoric acid. 3.46 3.07 
 
 Silica 0.78 1.32 
 
 77 
 
 IOO.OO IOO.OO 
 
 172. The ash contains all the mineral matter 
 which the plant derives from the soil, and is in a 
 good condition to be used again as plant-food. The 
 potassium and sodium salts are easily washed out 
 by rains, being very soluble in water. In the pro- 
 cess of making soap, ashes are leached for the pur- 
 pose of obtaining these two alkaline metals. Other 
 substances, however, remain, so that even leached 
 ashes are valuable as a manure. 
 
 173. A compost is simply a mixture of differ- 
 ent fertilizing materials. They are generally heaped 
 together and allowed to ferment, or decompose. 
 Organic matter, such as straw, chips, cotton-seed, 
 dead animals, refuse from slaughter-houses, etc., 
 must undergo decay or putrefaction before they be- 
 come valuable as manure, and in doing so they give 
 off ammonia which will be lost unless they be mixed 
 with earthy or other inorganic matter to absorb the 
 gas as fast as formed. Composting is the art of so
 
 7 g SCIENTIFIC AGRICULTURE 
 
 mixing these that a valuable fertilizer will be formed, 
 and no important constituents escape. Such mix- 
 tures of raw material must be kept moist, but must 
 not be exposed to rains that will dissolve out soluble 
 salts. On every farm or plantation properly man- 
 aged, all such substances will be preserved and re- 
 turned to the soil. 
 
 174. Pendleton, in his valuable work on "Scien- 
 tific Agriculture," gives good directions for such a 
 compost-heap, as follows : " A layer of stable-ma- 
 nure six inches thick, with a good sprinkling of 
 ground phosphate over it ; then a layer of cotton- 
 seed three inches thick (previously saturated with 
 water), and then another sprinkling of superphos- 
 phate, say half an inch thick ; then a layer of stable- 
 manure, and so on until the heap is completed, 
 which should be conical in form. Over the whole 
 heap, when sufficiently large, apply several inches of 
 dry clay soil, if you choose, which will absorb every 
 particle of the escaping ammonia. If, however, this 
 crust should become so saturated as to allow it to 
 escape, an additional coating of soil can be ap- 
 plied." 
 
 175. If the cotton-seed and superphosphate are 
 not on hand, use, with the stable-manure, the sweep- 
 ings of the yard, old mortar, leached ashes, bones, 
 scrapings from poultry-houses and yards, swamp 
 muck, the earth from old ponds, and any and every' 
 kind of waste matter that is usually thrown away or 
 hauled off that, it may not become offensive. Such
 
 ROTATION OF CROPS. 
 
 79 
 
 piles should be covered with a thin layer of earth, to 
 be added to whenever bad-smelling gases are found 
 to escape. 
 
 176. Professor Ville, a noted French writer on 
 fertilizers, calls a " complete manure" one that con- 
 tains nitrogen, potassium, phosphorus, and lime, in 
 suitable proportions to meet the demands of a given 
 crop. These four elements are the only ones likely 
 to be deficient ; and he advises farmers to purchase 
 the chemical salts containing these elements, and mix 
 them according to formulae given in his work on 
 "Chemical Manures." A good superphosphate with 
 nitre, or with some salt of ammonia, and one of po- 
 tassium, would constitute such a mixture. 
 
 CHAPTER IX. 
 
 ROTATION OF CROPS. 
 
 177. THE fact has long been known that it is not 
 best to grow the same kind of crop on the same 
 land for a number of years in succession. Thus, 
 the yield of corn, wheat, oats, tobacco, or other crop, 
 if grown on the same land without change will grad- 
 ually diminish, while if these crops be made to alter- 
 nate, that is, first one and then another, the aggre- 
 gate product will be much greater. This change is 
 called rotation of crops. 
 
 178. The advantages of rotation, or change of
 
 go SCIENTIFIC AGRICULTURE. 
 
 crops, result from the following considerations : In 
 the first place, different crops require elements in 
 different proportions ; one requires more potash than 
 another, or lime, or phosphoric acid, or nitrogen, or 
 some other constituent. By reference to the table 
 in paragraph 54, it will be seen that potatoes require 
 more potash than wheat or corn, while these require 
 more phosphoric acid ; clover and tobacco need a 
 great deal of lime, and so with other crops. A num- 
 ber of crops of potatoes in succession, without the 
 addition of potash in some form, will use up the 
 available supply, unless the quantity be very large. 
 Before this comes to pass, another crop that re- 
 quires less of potash but more of some other ele- 
 ment might grow well, while the potatoes would not 
 flourish. 
 
 179. In the second place, rotation of crops gives 
 time for the disintegrating action of the atmosphere, 
 rain, and frost to prepare new material from the 
 rock-particles in the soil, and get it in a form to be 
 used by the plant. One crop may use up the avail- 
 able food of a particular kind faster than it can be 
 prepared by these natural agencies. 
 
 1 80. In the third place, rotation, or change of 
 crop, when properly managed, enables one plant to 
 prepare food for another. Thus clover sends a long 
 tap-root deep down into the soil, and brings up food 
 to the surface. When the roots decay, the wheat- 
 plant that has surface-roots mainly can use the food 
 prepared by the clover.
 
 ROTATION OF CROPS. 8 1 
 
 181. In the fourth place, different .crops require 
 different modes of cultivation, so that the physical 
 properties of the soil are improved by rotation. 
 Grass-lands in a few years become hard and require 
 to be loosened up, which can be done by the culti- 
 vation of a crop of corn, followed by one of wheat, 
 and the re-sowing of grass. 
 
 182. Not only is a change of crops desirable, but 
 an occasional change of seed is found to be of great 
 benefit. Wheat grown on stiff clay-lands for some 
 years will be improved by getting seed from that 
 grown on sandy soil, and that on sandy soil by ob- 
 taining seed from wheat grown on stiff clay. An 
 occasional change of seed from one latitude to an- 
 other is alo found to be beneficial. 
 
 183. Crops that require the same elements in 
 about the same proportions should not follow each 
 other, nor those that are similar in their mode of 
 growth. Wheat and corn which depend mainly on 
 surface-roots will do well after clover, cotton, or to- 
 bacco, which have long tap-roots that extend down 
 into the subsoil. The greater the difference in the 
 constitution and character of two crops, the more 
 likely are they suited to follow each other. Climate 
 and soil have much to do in determining the best 
 rotation. 
 
 184. A good rotation for three years is 
 
 First year Corn 
 
 Second " Wheat 
 
 6 Third " Clover
 
 8 2 SCIENTIFIC AGRICULTURE. 
 
 A good four years' rotation is to allow the clover 
 to remain two years. In England, where corn is 
 not raised, a popular four years' rotation is 
 
 First year Turnips or other root-crop 
 
 Second " Barley 
 
 Third " Clover 
 
 Fourth " Wheat 
 
 A six years' rotation : 
 
 Clover Corn 
 
 Wheat, two years Wheat 
 Clover 
 
 185. For the tobacco-planter, a good rotation is 
 
 First and second year Clover 
 Third year Tobacco 
 
 Fourth " Wheat 
 
 This will keep the land fertile, or even improve 
 it. For the cotton-planter 
 
 First year 
 Second " 
 Third " 
 
 In much of the cotton-growing region in the 
 South, cotton is grown year after year without 
 change, to the great detriment of the land, except, 
 perhaps, in river-bottoms, where the soil is im- 
 mensely rich and very deep. 
 
 186. It is best in the above rotations not to re- 
 move the crop of clover, but let it lie on the ground, 
 and be turned under at the proper time. In fact, 
 there is no better way to improve land than by plow-
 
 ROTATION OF CROPS. 83 
 
 ing in the clover-crop after it has fallen on the 
 ground, and undergone partial decay. The long tap- 
 roots of this plant, as heretofore mentioned, go down 
 very deep, and work up a great deal of material as 
 food, and when the plant decays it furnishes all its 
 elements to wheat, corn, or other crop that may fol- 
 low. Old farmers know that, if land will only pro- 
 duce clover, it can be improved. 
 
 187. It was once thought that the advantages of 
 rotation are due in some measure to the excretion, 
 or giving out, of material by the roots of one plant 
 which serves as food to another. It is not believed 
 now that plants have the power to excrete, or give 
 out, any such material. Plants do have some power 
 of selection in taking in their food, for we know 
 that, when different plants are grown in the same 
 soil, they contain different proportions of the same 
 elements, but there is no proof that they all take in 
 the same substances and give out from their roots 
 what each does not need for growth. 
 
 1 88. No kind of rotation will secure good crops 
 if any one or more of the elements which a crop 
 needs be entirely absent from the soil, or if the food 
 is in such a condition that plants can not appropri- 
 ate it. In such cases, fertilizing, or manuring, is the 
 only way to restore such a soil or make it fertile. It 
 is true that wheat maybe grown for many years in suc- 
 cession on some qualities of land without manure, but 
 experience shows that the crop gradually diminishes 
 The exhaustion may be slow, but it will surely come
 
 84 SCIENTIFIC AGRICULTURE. 
 
 CHAPTER X. 
 
 THE SELECTION AND CARE OF LIVE-STOCK. 
 
 189. EVERY farmer and planter finds it absolutely 
 necessary to keep some kind of live-stock on his 
 farm or plantation. Such work as plowing and haul- 
 ing requires horses, mules, or oxen, while a variety 
 of products raised on every farm can only be made 
 profitable by being fed to cattle, sheep, and hogs, 
 and thus turned into beef, mutton, pork, and bacon. 
 The proper selection and management of such stock 
 become matters of great importance. Attention will 
 be called to a few guiding principles. 
 
 190. The kind of stock to be kept, above what 
 is necessary for the absolute wants of the farm in the 
 way of performing work, and furnishing food, will in 
 each case depend upon the system of farming adopted 
 as best suited to the nature and size of the farm. In 
 selecting stock, whether sheep, cattle, horses, or hogs, 
 the same common-sense principles should govern as 
 in other things. The best breeds, that is, those 
 best suited for particular purposes, should be se- 
 lected, as they are in general the most economical. 
 If the farmer wishes to raise beef, or mutton, or pork, 
 for the market, he should select those breeds that 
 can make the most flesh out of a given amount of 
 food. Meat-producing animals are machines for 
 converting vegetable food into flesh, and those breeds 
 that give the greatest yield with the least care and
 
 SELECTION AND CARE OF LIVE-STOCK. 85 
 
 expense of management are the best. If the produc- 
 tion of milk, or of wool, be the object in view, the 
 same principle should govern. 
 
 191. In the management of live-stock of every 
 sort, kind treatment is absolutely necessary to 
 success. A poor, half-starved, ill-used horse or cow 
 returns no profit to its owner, and is a disgrace to the 
 farmer. The feeding should be regular and uni- 
 form, and proper shelter from rain and cold should 
 be provided. Exposure retards the full, healthy de- 
 velopment of young animals, and prevents the con- 
 version of the food of older ones into salable prod- 
 ucts. As in the human system, so in the bodies of 
 lower animals, the digestive process, to be success- 
 fully carried on, requires good food, pure air, and 
 comfortable surroundings. 
 
 192. Plants derive their food from the soil and 
 work up the earthy, or inorganic, material into organic 
 products, such as sugar, starch, gum, oil, woody fibre, 
 gluten ; farm-animals derive their food from these 
 organic products, and form therefrom fat, muscle, 
 blood, and bones. The plant changes earthy mat- 
 ter, carbon dioxide, and ammonia, into organized 
 products in which is stored up a great deal of force 
 or energy; animals consume these organized prod- 
 ucts, which, in becoming disorganized in the body, 
 give out force or energy to the animal in the form of 
 heat and animal power. Plants store up energy 
 to be used by animals. 
 
 193. The body of an animal is much more com-
 
 86 SCIENTIFIC AGRICULTURE. 
 
 plicated in its structure than that of a plant. In the 
 higher animals it consists of a bony skeleton, covered 
 with flesh, through which runs a network of nerves 
 and blood-vessels. Within a portion of this skeleton 
 are placed the lungs and digestive organs. Solid 
 and liquid food passes through the mouth into the 
 organs of digestion, where the portion suitable for 
 conversion into flesh is made soluble by means of 
 proper secretions. This nutritive portion is absorbed 
 by suitable organs, carried into the blood, and then 
 distributed to all parts of the body, where it be- 
 comes flesh and bone by a mysterious process which 
 has never been explained. The operation is so deli- 
 cate and complicated, and so many organs or parts 
 are necessary to have it carried on successfully, that 
 it is no wonder animals cannot thrive when badly 
 treated. 
 
 194. It is well known that oxygen of the air is 
 as necessary for animal life as for the burning of 
 wood and coal in our fireplaces, and that air com- 
 ing from the lungs in breathing is charged with car- 
 bon dioxide. This can easily be shown by breathing 
 through clear lime-water by means of a glass or oth- 
 er tube. The water becomes milky, a result caused 
 by the carbon dioxide from the lungs combining 
 with the lime in solution to form insoluble calcium 
 carbonate. Just as the chemical action, or burning 
 of fuel in a fireplace or under a steam-boiler, pro- 
 duces heat and force, or energy, enough to move 
 machinery, so the chemical action within the body
 
 SELECTION AND CARE OF LIVE-STOCK. 87 
 
 produces animal heat and muscular energy. In fact, 
 no force, or energy, can be exerted by an animal 
 without the destruction or consumption of material, 
 and the heat of the body, like the heat of a fire, can 
 not be maintained without the burning of fuel of 
 some kind. 
 
 195. In cold weather, therefore, animals require 
 more substantial food than in warm weather, in order 
 to keep up a proper temperature of the body. Work- 
 animals also require more food than those that do no 
 work, in order to supply the necessary force, or en- 
 ergy. A certain amount of food is required to keep 
 up the ordinary heat, and sustain the daily " wear 
 and tear " of the body ; if the animal is expected to 
 grow or become fat, an additional supply is neces- 
 sary. All farmers know that hogs fatten faster, oth- 
 er things being equal, when kept in close pens, and 
 not allowed to run at large. The physical exercise 
 consumes much of the food that would otherwise go 
 to form fat. On the same principle, the stall-feeding 
 of cattle is economical. 
 
 196. Some years ago, Liebig, a noted German 
 chemist, divided the food of animals into two kinds, 
 heat-forming and flesh-forming. The first con- 
 tains no nitrogen, like sugar, starch, and fat; the 
 second contains nitrogen, like gluten and albumen. 
 Liebig taught that the first kind is used altogether 
 for keeping up the animal heat and forming fat, 
 while the second supplies force, and forms flesh, or 
 muscle. It is now believed that this theory is not
 
 8& SCIENTIFIC AGRICULTURE, 
 
 strictly true, as both kinds of food produce heat and 
 energy. It is true that an animal cannot live on 
 food that contains no nitrogen. A dog, or horse, 
 or other animal, will starve if fed on starch alone. 
 There must be a proper mixture of both nitrogenous 
 and non-nitrogenous food, to build up and sustain 
 the body. 
 
 197. Young animals, in whose bodies a rapid for- 
 mation of muscle is going on, require a great deal of 
 nitrogenous food, and all animals require more non- 
 nitrogenous, or carbonaceous food, in cold weath- 
 er than when the weather is warm. In very cold 
 countries, and during the winter in temperate cli- 
 mates, men will eat more fat meat than in summer. 
 The Esquimaux, a people that live in the intensely 
 cold regions of the frigid zone, drink oil and melted 
 fat, which are consumed in their bodies like fuel in 
 a stove or fireplace, and supply heat for the body. 
 
 198. Fat in animals, like starch, sugar, and oil 
 in plants, contains no nitrogen, and, when an animal 
 is not fed, this fat wastes away first in other words, 
 is consumed. If the animal be exposed to great cold 
 without extra food it cannot fatten. The reason, 
 therefore, that animals protected from the cold of 
 winter fatten much faster than when exposed, is, that 
 what would accumulate as fat is used in keeping the 
 animal warm. 
 
 199. The earthy, or inorganic matter, in plants is 
 as necessary for animal growth as the organic mat- 
 ter. The bony skeleton consists chiefly of calcium
 
 SELECTION AND CARE OF LIVE-STOCK. 
 
 89 
 
 phosphate, with a little calcium carbonate and oth- 
 er mineral substances derived from plants. While 
 plants contain everything necessary for animal 
 growth, some portions are richer in salts and nitrog- 
 enous material, and are therefore considered to be 
 of more value, as the grain of wheat, corn, and oats. 
 Foods differ greatly in value, as every farmer knows. 
 Many experiments have been made to determine the 
 feeding power of various kinds of food, and elabo- 
 rate tables have been drawn up to express their com- 
 parative value. Every farmer practically constructs 
 such a table for himself, at least, he sets a different 
 value on different substances, and buys and sells 
 accordingly. 
 
 200. In the following table, common hay is taken 
 as the standard, and the numbers opposite each sub- 
 stance show how many pounds of each contain 
 nourishment equivalent to ten pounds of hay : 
 
 Ibs. Ibs. 
 
 Common hay ..... 10 
 
 Clover hay 8 to 10 
 
 Green clover 45 to 50 
 
 Turnips 50 
 
 Cabbage 20 to 30 
 
 Peas and beans ... 3 to 5 
 
 Wheat-straw 40 to 50 i Wheat 5 to 6 
 
 Oat-straw 20 to 40 j Oats 4 to 7 
 
 Pea-straw 10 to 15 
 
 Potatoes . . 20 
 
 Corn 5 
 
 Oil-cake (linseed).. 2 to 4 
 
 Of course, such tables represent only general 
 results. Much depends on the quality of the food, 
 the form in which it is given, the condition of the 
 animal to which it is fed, and other circumstances 
 which the intelligent farmer understands.
 
 APPENDIX. 
 
 THE following simple directions are given for the benefit 
 of those who have no experience in science-teaching : 
 
 The exhibition of specimens of soils, plants, fertilizers, 
 etc., and the performance of even a few experiments, will 
 av/aken in the minds of pupils a lively interest in the sub- 
 ject, cultivate the power of observation, and render the 
 work of teaching pleasant and practical. Many illustra- 
 tions, in addition to those mentioned, will doubtless suggest 
 themselves to the minds of teachers. 
 
 The figures refer to corresponding numbers in the 
 text : 
 
 (i .) Show to the class a specimen of soil, place a little 
 on the end of a table-knife or spatula, and heat it over an 
 alcohol-lamp until the organic matter is burned off. 
 
 (2.) Exhibit to the class a sample of alluvial soil from a 
 creek or river bottom. 
 
 (3.) Exhibit pieces of sulphur, carbon, phosphorus, iron, 
 lead, silver, etc., to illustrate what is meant by an element. 
 
 (4.) Pulverize in a mortar a small quantity of potassium 
 chlorate, and mix with it about one-fourth its weight of 
 manganese dioxide (black oxide of manganese). Place the 
 mixture in a test-tube or small glass flask, and apply the 
 heat of an alcohol-lamp. Oxygen will be disengaged, as 
 may be shown by lowering into the flask or test-tube a 
 lighted splinter. The flame will be greatly increased, and.
 
 APPENDIX. 9I 
 
 if blown out, and the splinter be again thrust into the flask, 
 provided a spark be left, it will burst into flame. If a piece 
 of red-hot charcoal or burning sulphur be lowered into the 
 flask, it will burn with great energy. 
 
 (5.) Place a few scraps of zinc in a deep wineglass, and 
 pour over them a little water. Now pour in a little hydro- 
 chloric or sulphuric acid, and bubbles of hydrogen will rise 
 through the liquid. Bring a lighted match to the mouth of 
 the wineglass, and a slight explosion will ensue, caused by 
 the union of the escaping hydrogen with oxygen of the air. 
 By placing the zinc and acid in a bottle supplied with a 
 cork and glass tube, the hydrogen may be burned as it 
 issues from the tube, or may be collected in a receiver over 
 a pneumatic cistern. Be very careful not to light the escap- 
 ing hydrogen until all the air has been expelled from the 
 bottle, as a mixture of hydrogen with oxygen contained in 
 air unites with an explosion on application of flame. It is 
 always best to surround the bottle with a towel or handker- 
 chief before lighting the hydrogen. An explosion can then 
 produce no bad effects. 
 
 (6.) Remove the cork, and thrust a lighted splinter into 
 the bottle ; a slight explosion will occur, the splinter will be 
 extinguished, and again lighted as it is taken out, while the 
 hydrogen will continue to burn at the mouth of the bottle. 
 A small piece of burning candle lowered into the bottle 
 will show these results to better advantage. 
 
 (7.) Hold a tumbler or other glass vessel over the flame 
 of burning hydrogen, and the water produced will condense 
 on the cool surface. 
 
 (8.) Dissolve some sugar or salt in a tumbler of water. 
 
 (9.) Float a piece of cork on the surface of water, and 
 place on it a small pellet of phosphorus. Now light the 
 phosphorus, and cover it quickly with a glass receiver or
 
 9 2 SCIENTIFIC AGRICULTURE. 
 
 wide-mouthed bottle, the mouth dipping under the surface 
 of the water. After the phosphorus has ceased burning, 
 the water will absorb the white fumes of the phosphorus 
 oxide, and rise in the bottle. The gas which remains is 
 nearly pure nitrogen. A lighted splinter or candle if brought 
 into the nitrogen will be extinguished. 
 
 (10.) Rub together in a mortar a little ammonium chlo- 
 ride (sal-ammoniac) and quicklime. Ammonia will be given 
 off, which can be detected by its pungent odor. Bring a 
 piece of red litmus-paper in contact with this gas, and it 
 will turn blue immediately. 
 
 (n.) Place a few bits of copper in a wineglass, and 
 pour over them a little nitric acid. Red fumes of nitrogen 
 tetroxide will be formed. The blue liquid that is left con- 
 tains copper nitrate. 
 
 (12.) Dip a piece of paper in spirits of turpentine and 
 light it. The black smoke consists of finely divided carbon. 
 Hold a piece of window-glass over the flame of a candle, 
 pushing it down upon the flame, and it will soon be coated 
 with carbon. 
 
 (13.) Place some small pieces of marble or limestone in 
 a deep wineglass or bottle, and pour over them a little 
 hydrochloric acid. The brisk effervescence that takes place 
 is caused by the escape of carbon dioxide. A burning 
 splinter or candle will be extinguished if lowered into the 
 bottle. 
 
 (14.) Bum a small piece of sulphur, and hold a red rose 
 or other flower over the fumes. The flower will be bleached. 
 A similar effect may be produced with a sulphur-match. 
 
 (15.) Place a splinter of wood in strong sulphuric acid, 
 and it will turn black. The acid does not act on the car- 
 bon of the wood. Pour a little of the strong acid into a 
 wineglass of water, and the water will become very hot,
 
 APPENDIX. 
 
 93 
 
 caused by its union with the acid. Caution should be ob- 
 served in pouring this acid into water, and care be taken 
 not to pour the water into the acid. 
 
 (16.) Exhibit a piece of phosphorus, and show how 
 easily it can be set on fire. 
 
 (17.) Rub a match, and show how the friction causes it 
 to inflame. 
 
 (18.) Place a little phosphorus on a dry plate, set it on 
 fire, and quickly place over it a receiver, or wide-mouthed 
 bottle. The white fumes that rise are phosphorus pent- 
 oxide. Water unites with this oxide to form phosphoric 
 acid. 
 
 (19.) Place some manganese dioxide (black oxide of 
 manganese) in a glass flask or test-tube, pour over it some 
 strong hydrochloric acid, and apply a gentle heat. Chlo- 
 rine, a yellowish-green gas, will be disengaged. By means 
 of a properly bent glass tube reaching to the bottom of a 
 bottle, this gas may be collected by displacement. Im- 
 merse in it a lighted taper or splinter, and the light will be 
 extinguished. A red rose moistened and placed in a bot- 
 tle of chlorine will be bleached in a short time. 
 
 (20.) Heat in a test-tube, or small flask, a little potas- 
 sium iodide, manganese dioxide, and sulphuric acid. The 
 beautiful violet-colored vapor of iodine will be disengaged. 
 Substitute potassium bromide for the potassium iodide, and 
 the deep-red vapor of bromine will be given off. 
 
 (21.) Drop a small piece of potassium on the surface of 
 water. The metal will burn with a violet flame. Place a 
 small piece of potassium on the wick of an alcohol-lamp, 
 touch it with a piece of ice, and the lamp will be lighted. 
 
 (22.) Drop a piece of sodium on the surface of water. 
 It will move around, decomposing the water with the dis- 
 engagement of hydrogen. Place a piece in a few drops of
 
 94 
 
 SCIENTIFIC A GRICUL TURE. 
 
 water sprinkled on a board, and the sodium will burst into 
 flame of a deep-yellow color. 
 
 (23.) Color some water blue with litmus. Add a drop 
 of acid to turn it red, and then drop a piece of potassium 
 or sodium on the surface. The blue color will be restored 
 as the metal is consumed. 
 
 (24.) Heat in the flame of an alcohol-lamp a piece of 
 magnesium ribbon, and show the brilliancy of its combus- 
 tion. 
 
 (25.) Collect samples of different varieties of soils, and 
 exhibit them to the class. 
 
 (26.) Heat some green leaves or grass on a spatula, me- 
 tallic plate, or small shovel, until nothing is left but the ash. 
 
 (27.) Exhibit specimens of sugar, starch, albumen, or 
 white of egg, etc. 
 
 (28.) Pour some clear lime-water into a wineglass, and 
 by means of a straw or glass tube breathe through the 
 liquid. The milky appearance is caused by the carbon 
 dioxide from the lungs combining with the lime, and form- 
 ing insoluble calcium carbonate. 
 
 (29.) Collect, and show to the class, a few plants with 
 root, stem, and leaves. 
 
 (30.) Pour some water on a lump of unslaked lime. 
 In a few minutes the mass will become hot, combine with 
 a portion of the water, and crumble into powder. 
 
 (31.) Pour some hydrochloric acid on marl, and effer- 
 vescence will take place, caused by the escape of carbon 
 dioxide. 
 
 (32.) Mix a tablespoonful of plaster of Paris with a lit- 
 tle water, and show how it sets, or hardens. 
 
 Exhibit to the class specimens of as many different fer- 
 tilizers as can be obtained.
 
 QUESTIONS. 
 
 THE following questions are intended merely to direct 
 attention to the more important points in the text. Intelli- 
 gent teachers will not, of course, confine themselves to any 
 set form of questions, but secure as far as possible a mas- 
 tery of the subject. 
 
 CHAPTER I. 
 
 THE DEVELOPMENT OF SCIENTIFIC AGRICULTURE. 
 
 1. What is agriculture? As an art, what does it teach? 
 What, as a science ? 
 
 2. How does it rank as an industrial pursuit ? Why has it 
 always been first in importance? 
 
 3. Why was less cultivation of the soil required in the early 
 ages of the world ? Where did men obtain food and clothing ? 
 What effect had the increase of population ? 
 
 4. What is said of the progress of agriculture as a science ? 
 Why do some men say that practical and scientific farming are 
 different ? 
 
 5. Why has the progress of agriculture as a science been 
 slow ? What great men are mentioned as having been farmers 
 or having written on farming? What is necessary to accomplish 
 great results in any science ? 
 
 6. What other reason is given for the slow progress of agri- 
 culture as a science ? What is botany ? Why should a farmer 
 know something of it ?
 
 9 6 SCIENTIFIC AGRICULTURE. 
 
 7. What is zoology ? Why should the farmer know some- 
 thing of this science? What does geology treat of ? Why 
 should the fanner study it? With what does the mechanic 
 supply the farmer? What does physics treat of? Why should 
 the farmer have some knowledge of chemistry ? 
 
 8. Why should the farmer have a general acquaintance with 
 the sciences mentioned ? What relation do they sustain to agri- 
 culture ? 
 
 9. What sciences are of most importance to the farmer? 
 What improvements in farming implements are mentioned ? 
 
 10. What benefits has agriculture derived from chemistry ? 
 n. How does the chemist proceed in his investigations? 
 
 What is it proposed to show ? 
 
 CHAPTER II. 
 
 THE ORIGIN, COMPOSITION, AND CLASSIFICATION OF SOILS. 
 
 12. What is the soil? Of what does it consist? Where 
 does the organic matter come from ? When burned, what is 
 left ? What do geologists suppose the earth to have once been ? 
 What happened as it cooled down ? Of what does soil consist ? 
 
 13. What is meant by mechanical agencies ? What by 
 chemical? Give examples? Are these agencies always at 
 work? 
 
 14. What is included under the term "rock"? What 
 agencies disintegrate rocks? How does water act? How 
 does thorough cultivation help this disintegrating action ? 
 
 15. With what do the elements of a soil vary ? Does the soil 
 always rest on the rock from which it was formed ? What is an 
 
 16. What causes the difference in the quality of soils ? Are 
 there many simple substances ? 
 
 17. How many elements are certainly known ? Which are 
 gases ? Liquids ? Solids ? Are there any permanent gases ? 
 
 18. How many elements are concerned in the growth of
 
 QUESTIONS. 97 
 
 plants? Name the non-metallic elements. The metals. What 
 other elements are sometimes present? 
 
 19. What is said of oxygen ? How prepared ? What should 
 be mixed with the potassium chlorate ? 
 
 20. Properties of oxygen ? What is combustion ? Give ex- 
 amples. 
 
 21. With what elements does oxygen unite? What are 
 these compounds called? How named? What is potash? 
 What is lime? 
 
 22. Give cases of oxidation without light and intense heat? 
 What happens in breathing? Can animals live without oxy- 
 gen ? Can plants ? 
 
 23. What is said of hydrogen? How is it prepared ? 
 
 24. Properties of hydrogen ? Result of its combustion ? 
 
 25. How is water formed? What does it form when con- 
 densed in the air? Where do natural waters get the mineral mat- 
 ter contained in them ? What kind of water is the purest? Why? 
 
 26. Where is nitrogen found ? How much is in the air ? 
 How is it prepared ? 
 
 27. Properties of nitrogen? Is it poisonous? How can 
 oxygen, hydrogen, and nitrogen, be distinguished ? 
 
 28. What is ammonia? How made? How much does 
 water absorb ? What is hartshorn ? Why is ammonia called 
 an alkali ? 
 
 29. How is ammonia formed naturally? How does it get 
 into plants ? 
 
 30. What is nitric acid ? What does it form with metals ? 
 What is nitre? Chili saltpetre? How used? 
 
 31. In what forms does carbon exist? Is it abundant in 
 plants ? What per cent, in sugar ? In turpentine ? What 
 makes smoke black ? 
 
 32. What is carbon dioxide ? Where found ? What are its 
 properties ? 
 
 33. What is silicon ? Is it necessary to plants ? Where 
 is it found ?
 
 9 8 SCIENTIFIC AGRICULTURE. 
 
 34. What is sulphur? What does it form in burning? Its 
 use ? What is sulphuric acid ? What are its compounds 
 called? Give examples. 
 
 35. What is phosphorus ? Where found ? Why must it be 
 kept under water? Its use ? How does a match burn? 
 
 36. What is phosphoric acid ? What is calcium phosphate ? 
 What does it form ? Why must soil contain phosphorus ? 
 How can it be supplied ? 
 
 37. What is chlorine ? What is hydrochloric acid ? How 
 is chlorine separated ? Its properties? Uses? Where found? 
 
 38. What is iodine ? Bromine? To what are they similar ? 
 Properties of fluorine ? Where found ? 
 
 39. What is potassium? How kept? Why? What effect 
 has water on it ? What is caustic potash ? What do all acids 
 contain ? How are salts of potassium formed ? Where found ? 
 
 40. Describe sodium. How does it act on water ? What 
 is common salt ? Where found ? In what respects are caustic 
 potash and soda similar to ammonia ? Their use ? 
 
 41. Describe calcium ? Lime ? What are marble, lime- 
 stone, and chalk ? How changed to lime ? What is gypsum "t 
 
 42. Describe magnesium and aluminum. Where found ? 
 What are its properties ? 
 
 43. Ores of iron ? For what purpose used ? Where is iron 
 found ? What is said about manganese ? 
 
 44. How is the composition of a soil generally given ? Is 
 it easy to analyze a soil ? 
 
 45. What constituent exists in the largest proportion in the 
 analysis given ? What in the smallest ? 
 
 46. How much organic matter is found in soils ? What ele- 
 ments are likely to be deficient ? 
 
 47. How may soils be classified ? 
 
 48. What are calcareous soils ? Peaty ? Heavy ? Light ? 
 
 49. How deep is the soil generally ? What is the sub-soil I 
 How may the depth of soil be increased ? Its advantages ?
 
 QUESTIONS. 99 
 
 CHAPTER III. 
 
 THE COMPOSITION OF PLANTS. 
 
 50. How many elements are found in plants ? What are 
 they? 
 
 51. What element in soils is not in plants ? What in plants 
 and not in animals ? 
 
 52. What effect has heat on plants ? How much water in 
 turnips, cabbages, and potatoes ? In cured hay ? What is ash ? 
 
 53. What four elements are consumed when a plant is 
 burned ? Why called organic ? What becomes of them ? 
 
 54. What becomes of phosphorus and sulphur ? Chlorine 
 and silicon ? How much ash in wood ? In tobacco ? Corn ? 
 Which has in it the most phosphorus oxide, the ash of corn or 
 potatoes ? Chlorine ? Potassium oxide ? 
 
 55. What are ultimate elements ? Proximate ? Name some. 
 
 56. What are amylaceous and saccharine substances ? Of 
 what elements are they composed ? Where is cellulose found ? 
 How converted into sugar ? 
 
 57. What are pectose substances ? Where found ? 
 
 58. Name some vegetable acids. What elements in them ? 
 
 59. Where are fats and oils found ? How do they differ 
 from sugar ? What else are included in this group ? 
 
 60. How do the albuminoid or protein groups differ from 
 those mentioned ? Where is pure albumen found ? What do 
 botanists mean by " albumen " ? Where is gluten found ? 
 Vegetable casein ? 
 
 61. How many elements are in these compounds ? What 
 has a knowledge of their chemical constitution done ? 
 
 62. How do starch and sugar differ ? Where is starch 
 found ? 
 
 63. How does grape-sugar differ from starch ? Where does 
 the change of one into the other take place ? How can cotton 
 be changed into sugar? 
 
 64. What takes place in the leaf?
 
 T.OO SCIENTIFIC AGRICULTURE. 
 
 65. Which crop mentioned in the table has the most starch ? 
 Albuminoids ? Fat ? Woody fibre ? Ash ? 
 
 66. Are the ash constituents important ? What becomes 
 of the products of combustion ? What does a plant carry from 
 the soil ? What is the ultimate effect ? 
 
 67. What does Liebig mean by a system of spoliation ? 
 What elements are scarcely ever deficient ? In what condition 
 may they exist ? How can this be remedied ? 
 
 68. What elements are likely to be deficient ? Can the soil 
 produce when any of the essential elements of plants are ab- 
 sent? 
 
 69. What does chemistry teach the farmer ? For what 
 must it not be held responsible ? 
 
 70. By what must the fanner be guided ? 
 
 CHAPTER IV. 
 THE COMPOSITION AND PROPERTIES OF THE ATMOSPHERE. 
 
 71. What does the atmosphere contain ? 
 
 72. Is the air uniform in composition ? In what condition 
 are its constituents ? 
 
 73. What is said of watery vapor ? Whence does it rise ? 
 What does it form when condensed ? 
 
 74. The character of nitrogen ? Of oxygen ? The effect 
 of carbon dioxide on animals ? On plants ? 
 
 75. How is carbon dioxide formed ? What prevents its ac- 
 cumulation in the atmosphere ? What change takes place in 
 it when absorbed by the leaves of plants ? 
 
 76. How does carbon dioxide get into the leaves ? Through 
 what influence is it decomposed ? 
 
 77. How much carbon dioxide exists in the atmosphere ? 
 What says a distinguished chemist ? 
 
 78. How much ammonia is in the atmosphere ? 
 
 79. To what is the atmosphere adapted ? What benefits 
 are derived from it ?
 
 QUESTIONS. I0 i 
 
 80. What does science teach in reference to the atmospheric 
 agencies ? To what do they contribute ? The effect of their 
 action on solid substances ? 
 
 81. The effect of the atmosphere on organic and inorganic 
 matter ? On a dead animal or plant ? 
 
 82. What knowledge is necessary to understand the growth 
 and development of plants ? 
 
 CHAPTER V. 
 THE SOURCES OF PLANT-FOOD AND HOW OBTAINED. 
 
 83. The sources of plant-food ? What elements are found 
 in air ? 
 
 84. Why cannot carbon enter the plant in a pure state ? In 
 what form is it a gas ? How does it enter ? Why do plants 
 grow faster in daytime than at night ? Where does the carbon 
 of plants come from ? 
 
 85. How do hydrogen and oxygen get into plants ? 
 
 86. How nitrogen ? Does free nitrogen contribute to 
 growth ? Where is it gotten ? 
 
 87. How much nitrogen do plants contain ? How much is 
 in a ton of hay ? Why must it be supplied in the form of salts 
 containing nitrogen ? 
 
 88. Why are the four elements mentioned called organic ? 
 What are the other constituents called ? How do they get into 
 plants ? In what form ? 
 
 89. What are the main parts of a plant ? What does the 
 seed contain ? What does it require for germination ? How 
 does it germinate ? 
 
 90. How does the root grow ? What may be regarded as 
 the lungs of a plant ? What the mouth ? What is said of the 
 roots spreading ? What is necessary for a plant to be thrifty ? 
 Why must its food be near at hand ? 
 
 91. How did Schubert determine the extent of the roots of 
 plants ? How deep did he find the roots of wheat to extend ? 
 What is the total length of the roots of a barley-plant ?
 
 102 SCIENTIFIC AGRICULTURE. 
 
 92. What increases the absorbing surface of roots ? Are 
 there such organs as " spongioles " ? 
 
 93. How many kinds of roots are there ? What is said of 
 the mulberry-tree ? What of cornstalks ? 
 
 94. Have roots the power of " excretion " ? Of selection ? 
 
 95. What is evident from what has been said about roots ? 
 By what should the farmer be guided ? 
 
 CHAPTER VI. 
 THE IMPROVEMENT OF SOILS. 
 
 96. What power has inert matter ? What has the seed ? 
 Do we know what the life-principle is ? 
 
 97. Do we understand the connection between the growth 
 of a plant and its surroundings ? What has chemistry taught ? 
 
 98. What is necessary to insure fertility ? What vague no- 
 tions have some men ? 
 
 99. What have some writers asserted ? Is it true ? What 
 can we not control ? 
 
 100. What has science done ? 
 
 101. What of sewage ? What does a perfect system of agri- 
 culture require ? 
 
 102. Upon what are all scientific methods founded ? To 
 what addressed ? What soil cannot be improved ? What can 
 be? 
 
 103. What means can be used for the improvement of soils ? 
 What are mechanical? What chemical? The effect of the 
 first ? Of the second ? 
 
 104. What system of drainage is the cheapest ? 
 
 105. What are the benefits of drainage? 
 
 106. What are the advantages of deep plowing and sub- 
 soiling ? 
 
 107. What additional advantage is mentioned ? What care 
 should be taken ? 
 
 108. Mention an economical and effective method of sub- 
 soiling.
 
 QUESTIONS. I03 
 
 log. What other mechanical means of improvement are men- 
 tioned ? What is the great object to be accomplished ? What 
 feeling generally prevails in a new country ? 
 
 no. Is thorough cultivation always proper? 
 
 CHAPTER VII. 
 
 THE USE OF MANURES, OR FERTILIZERS. 
 
 in. Upon what principles is the use of fertilizers based ? 
 
 112. When should fertilizers be used ? 
 
 113. What produces exhaustion ? How much potash is re- 
 moved in a ton of red-clover hay ? How much phosphoric acid ? 
 
 114. How much phosphoric acid is contained in an ox 
 weighing 1,000 pounds ? How much potash in 1,000 pounds 
 of unwashed wool ? 
 
 115. Upon what does the rapidity of exhaustion depend ? Is 
 it sure to follow without restoration ? 
 
 116. How many kinds of fertilizers are there ? 
 
 117. Why is a decaying plant a good fertilizer ? How do 
 vegetable substances benefit land ? 
 
 118. How do cornstalks serve as a fertilizer? 
 
 119. What is said of cotton-seed ? Leaves ? 
 
 120. What two important constituents are found in cotton- 
 seed ? How much mineral matter in a bale of lint ? In cot- 
 ton-seed from a bale ? 
 
 121. If the seed be returned to the soil, is cotton an exhaus- 
 tive crop ? What escapes from fermenting seed ? Why should 
 it be preserved ? 
 
 122. How should seed be applied ? 
 
 123. Is the oil in cotton-seed valuable as a fertilizer ? Why 
 not? 
 
 124. What are the good effects of grinding the seed ? How 
 can its constituents be preserved ? 
 
 125. What important object should be accomplished on 
 every farm ?
 
 104 
 
 SCIENTIFIC AGRICULTURE. 
 
 126. What are animal fertilizers ? Are they valuable ? 
 
 127. What is said of the bones and excrements of animals as 
 fertilizers ? 
 
 128. What is the composition of bones ? 
 
 129. How are they sometimes used ? 
 
 130. How are they converted into superphosphate ? 
 
 131. What does sulphuric acid form with calcium ? 
 
 132. Where has a large deposit of bone phosphate been 
 found ? 
 
 133. What other source of superphosphate is mentioned ? 
 
 134. How can a good superphosphate be made by the 
 tanner ? 
 
 135. Give the directions of Dr. Nichols for making it. 
 
 136. What is said of guano and its use in South America ? 
 
 137. What is guano ? 
 
 138. When was it introduced into Europe ? 
 
 139. What does Liebig say of its use ? 
 
 140. When was it brought to the United States ? 
 
 141. Why is the Peruvian guano the best ? 
 
 142. What makes guano so rich a fertilizer ? 
 
 143. Give the composition of guano. 
 
 144. How does Peruvian guano differ from the African ? 
 
 145. Give its properties. 
 
 146. To what is its stimulating effect due ? 
 
 147. What retards the growth of plants ? Is nitrogen sup- 
 plied from the air ? 
 
 148. How does guano act ? Why does it sometimes " run 
 out"? 
 
 149. With what sort of fertilizers is it generally mixed ? 
 
 150. Why should it not be placed next to the seed ? 
 
 151. What is mentioned as a good mixture? How should 
 it be applied ? 
 
 152. Should guano be mixed with lime ? Why not ? 
 
 153. What is said of farm-yard manure ? 
 
 154. Upon what does its value depend ? How can the es- 
 cape of ammonia be determined ? How prevented ?
 
 QUESTIONS. I05 
 
 155. How should manure-heaps be managed ? What should 
 be added ? 
 
 156. What is said of human excrements ? 
 
 157. Why are animal manures richer than vegetable ? 
 
 CHAPTER VIII. 
 
 MINERAL FERTILIZERS. 
 
 158. What mineral fertilizers are mentioned ? 
 
 159. How is lime made ? 
 
 160. What is slaked lime ? What effect on it has long ex- 
 posure to air ? 
 
 161. In what condition is the water in slaked lime ? Its 
 properties ? How does mortar harden ? 
 
 162. What is the use of lime as a fertilizer ? 
 
 163. What is marl ? How valued ? 
 
 164. What is said of green-sand marl ? Composition of 
 marl ? 
 
 165. What sort of lands are well suited for marl ? 
 
 166. What is gypsum ? What effect has heat upon it ? 
 How does it harden ? Its use ? 
 
 167. How found ? Its properties ? How applied ? 
 
 168. Why does it not injure seeds ? Why should it not be 
 mixed with superphosphate ? 
 
 169. What is common salt ? How does it act ? 
 
 170. What are salts ? What is said of the utilization of 
 waste products ? 
 
 171. How much potash in the ashes of the oak ? Beech ? 
 
 172. Why are ashes a good fertilizer? 
 
 173. What is a compost ? How made ? 
 
 174. What directions are given by Pendleton for compost- 
 ing with cotton-seed ? 
 
 175. How can a good compost be made from materials on 
 every farm ? 
 
 176. What does Professor Ville call a " complete manure "?
 
 106 SCIENTIFIC AGRICULTURE. 
 
 CHAPTER IX. 
 
 ROTATION OF CROPS. 
 
 177. What is meant by rotation ? 
 
 178. What are its advantages ? Give illustrations. 
 
 179. What other advantage is mentioned ? 
 
 1 80. Give a third advantage of rotation. 
 
 181. Give a fourth advantage. 
 
 182. What is said of change of seed ? 
 
 183. What crops should not follow each other ? What prin- 
 ciple should govern ? 
 
 184. Mention a good three years' rotation. A four years' 
 rotation. An English rotation. 
 
 185. A rotation for the tobacco-planter. For cotton-planter. 
 186 What is best to be done with the clover ? Why ? 
 
 187. Have plants the power of secretion ? Of selection ? 
 
 188. When will rotation certainly fail ? How can such 
 land be restored ? 
 
 CHAPTER X. 
 
 THE SELECTION AND CARE OF LIVE-STOCK. 
 
 189. Why must every farmer have live-stock ? 
 
 190. Upon what will the kind of stock to be kept depend ? 
 What sort should be selected ? Why ? 
 
 191. What is necessary in the management of live-stock ? 
 Why? How should it be fed? Why should exposure be 
 avoided ? 
 
 192. Difference between the functions of plants and animals ? 
 
 193. How do animals digest their food and convert it into 
 bone and muscle ? 
 
 194. What gas is formed in respiration ? How shown ? 
 
 195. Why should animals require more food in cold than in 
 warm weather ? Why more when at work ?
 
 QUESTIONS. I0 7 
 
 196. What is Liebig's division of food ? Is his theory strict- 
 ly true ? 
 
 197. What sort of food do young animals need ? 
 
 198. What first wastes away when an animal is not fed? 
 Why do animals protected from cold fatten faster ? 
 
 199. What is the chief constituent of bones ? Whence de- 
 rived? 
 
 200. How does wheat-straw compare with hay as a food for 
 stock ? Upon what do the good effects of food depend ? 
 
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