UNIVERSITY OF CALIFORNIA agricultural Experiment Station College of agriculture e - j - wickson, director BERKELEY, CALIFORNIA CIRCULAR No. 58 November, 1910 EXPERIMENTS WITH PLANTS AND SOILS IN LABORATORY, GARDEN, AND FIELD By FRANK E. EDWARDS, M.S. Instructor in Agricultural Chemistry, California Polytechnic School, San Luis Obispo, California LIST OF EXERCISES. THE PLANT AND ITS WORK. PAGE Exercise 1. — Moisture in the Plant 5 2. — Composition of the Dry Matter of Plants 6 3. — Composition of Plant Ash 7 4. — Nitrogen in Plants 8 5. — Transpiration of Water from the Plant 9 6. — Transpiration is through the Leaf 9 7. — Circulation in the Plant 9 8. — Sunlight and the Plant 10 9. — Air and the Plant 10 10.— How the Plant gets its Food 10 11. — Tests for the Principal Classes of Plant Compounds 11 12. — Conditions Necessary for Germination 12 13. — Plump and Shrunken Seeds 12 14.— Seed Testing 12 15. — Soil Compacting and Germination 13 16. — The Depth of Germination 14 THE SOIL AND ITS RELATION TO PLANTS. 17. — The Soil and the Subsoil 15 18.— Rock Powder 15 19. — Plant Growth on Eock Surfaces 15 20.— Humus in Soils 16 21. — Sand, Silt, and Clay in Soils 16 22. — Soil-forming Minerals 19 23. — Local Minerals 19 24.— Alkali 19 25. — Gypsum Treatment for Black Alkali Soils 20 26. — Local Alkali Lands 21 27. — Alkali and Acid Soil Tests 21 28. — Nitrogen Nodules 22 29. — Classifying Local Soils According to Location 23 30.— Sampling Soils 23 31. — Moisture in the Soil 24 32. — Collecting Local Soil Samples 25 33. — Water holding Capacity of the Soil 25 34. — Organic Matter and Water holding Capacity 25 35. — Size of Particles and Water holding Capacity 26 36. — Capillarity 26 37.— Soil Capillarity 27 38.— Porosity of the Soil 27 39.— Shrinkage of Clay Soils 28 40. — The Relation of Color to Soil Temperature 28 41. — The Relation of Evaporation to Soil Temperature 28 42. — The Relation of Mulches and Cultivation to Evaporation 29 43. — Wind Breaks and Soil Moisture 30 44. — Fertilizers 30 45. — The Absorption of Manure Leachings by the Soil 30 46. — Fertilizer Field Tests 31 47. — Manure and Gypsum Field Tests 32 48.— Orchard Fertilizer Tests 32 49. — Crop Rotation 32 50.— Weeds 33 INTRODUCTION. Since the beginning of my connection with secondary work eight years ago I have believed that some soil study can with advantage be presented to pupils in the first year of the high school. Among the chief reasons for this early study are, the value of securing their in- terest in agriculture as soon as possible; the fact that many pupils attend but one year and if no agriculture be taught in the first year they receive no instruction therein; and the educational value of de- termining for themselves by means of simple experiments the reasons for natural phenomena often seen but not understood by them. To one who has received a college training in soils and soil fertility it is often difficult to conceive of any study of soils not preceded by chem- istry and physics. It is one of the difficulties and misfortunes of a highly technical training not to be able to appreciate and to present the basic principles of a science so simply as to be understood by the young mind. Mr. Edwards has been teaching agriculture for three years in the California Polytechnic School as he presents it in these pages. The exercises are therefore not theoretical but a part of his actual work in presenting the subject of soils and elementary agri- culture to first year pupils. Pupils are admitted to the Polytechnic from the grammar grades and thus his experience is fully comparable with that of any teacher of agriculture in the regular high school. Aside from the experiments dealing with chemical elements and others which may need to be demonstrated by the teacher, the pupil should perform all with his own hands. It is hoped that the teacher may find the exercises especially help- ful as supplementary work in general science, physical geography, or botany. To the end that greater progress may be made in agricultural teaching we would appreciate suggestions from teachers as to their experience in using the exercises. LEROY ANDERSON. EXERCISES IN ELEMENTARY AGRICULTURE Modern Agriculture is a many sided and intricate science, but primarily it has to do with the growth of plants. The object of this circular is to set forth a few simple experiments that will be of in- terest to students in our Secondary Schools, and create in them a de- sire to understand the laws that control the growth and development of the plant — one of the most wonderful of all created things. THE PLANT AND ITS WORK. The normal plant is a stay-at-home. Its roots are firmly planted in the ground, so that it could not travel if it would. Necessity, then, requires that it shall live entirely on the food that it can select from its surrounding mediums — the soil which covers its roots, the air and water which fill the pore spaces in the soil, and the air which envelops its stem and branches. Exercise one and two will show the constitu- ents of the plant — the materials gathered from these three sources. Exercise 1. — Moisture in the Plant. Apparatus : A small pan or a can lid with a capacity of 100 c.c. to 150 c.c, a balance sensitive to 10 milligrams, weights for balance, sheet iron drying oven, thermometer, gas burner or other source of heat. Dry the pan and weigh it carefully. Nearly fill it with the finely cut stem and leaves of a fresh plant that is growing vigorously. Weigh again. Record all weights. Get the weight of the plant material by difference. Place the pan in the oven and keep the temperature at 100° to 105° C. for five or six hours. Cool and weigh. Heat in the oven again for an hour and again cool and weigh. If the weight is constant the material is dry. If there is an appreciable difference shown by the two weighings, repeat the heating, cooling and weigh- ing till a constant weight is shown. The total loss in weight repre- sents the amount of water held mechanically by the plant. Calculate the amount in percent of the original weight of the plant material. Tell some ways in which this mechanically held water is of use to the plant. Our ordinary growing plants hold from 75% to 95% of water in this way. Save the dry material for Exercises two and four. Exercise 2. — Composition of the Dry Matter of Plants. Apparatus : Porcelain crucible No. 0, 250 c.c. flask, gas or alcohol burner, wire triangle, iron tripod or ring stand. Nearly fill the crucible with dried plant material and heat it over the burner till the substance begins to blaze. Remove the burner and quickly hold over the blazing material the flask, nearly full of cold water and clean and dry on the outside. Note the condensation of water on the cold surface of the flask. As the material used was dry, this water must have been produced by the breaking up of the plant tissues. It consists of Oxygen and Hydrogen, two elements of plant composition. This, as well as the mechanically held water was de- rived from the soil water, having risen through the roots. Remove the flask and observe the charred mass remaining in the crucible. It is principally carbon and is derived from the air. Continue to heat the crucible till there remains only a light, gray colored ash. These ashes show the part of the plant that is derived from the soil. How does it compare in amount to the part derived from the water and air (the part that has burned away) ? Save the plant ash for Exercise three. The average plant derives about 9.0% of its weight from the air, 89.5% from the water and 1.5% from the soil. The air always sup- plies its portion of the plant food without the assistance of the farmer ; our California soils are generally quite fertile and with proper meth- ods of cultivation will usually yield their part of the food; but to supply the large amount of water that the plant soil requires, offers a problem that is becoming very serious, and one to which we are prone not to give proper consideration. Chemical Elements in Plants. Chemists have studied the matter that makes up this world of ours until they have reduced it to about eighty simple substances which they term elements. More than half of these elements are rare and are of minor importance to agriculture. Only ten elements seem to be necessary for plant growth. They are : potassium, calcium, mag- nesium, iron, sulphur, phosphorus, carbon, oxygen, hydrogen and nitrogen. Carbon is derived from the carbon dioxide in the air; hydrogen and oxygen from the water taken into the plant ; and the other seven come from the soil. Of the soil elements potassium, phos- phorus and nitrogen, and sometimes calcium, are used by the plant to such an extent that it becomes necessary to supplement what is in the soil with fertilizers. Besides the elements named, sodium, silicon and chlorine are found in all plants, but according to the best authori- ties they seem to serve no useful purpose. Another element which is of importance to agriculture is aluminum. It is not a plant food, but as one of the principal constituents of clays it is a very important factor in plant growth. The clay in a soil serves to hold and give to the plant some of its food that would otherwise be washed away. None of the above named elements are found in the plant or in the soil in the simple or elemental form, but are always combind with other elements to form chemical compounds. If the students have not had experience in making chemical tests the teacher may make the following tests for the class. Exercise 3. — Composition of Plant Ash. Apparatus : Evaporating dish, funnel, filters, test tubes, three inches of platinum wire (fine iron wire may be used), cobalt blue glass (or a blue glass bottle), glass stirring rod. Place in an evaporating dish about one-half gram of the plant ash left from exercise two. Add to it 5 c.c. each of distilled water and strong hydrochloric acid, and a few drops of strong nitric acid. A rapid frothing, or effervescence, when the acid is added, proves that carbon is a constituent of the ash. Heat the mixture to boiling and evaporate it nearly to dryness. Add 10 c.c. distilled water and stir well with a glass rod. The small amount of white insoluble matter contains the silicon of the plant ash. Filter and wash the residue on the filter with a little distilled water and add the washings to the filtrate. To this add ammonia with constant stirring till the solu- tion smells strongly of the ammonia, and heat to boiling. Filter and wash the residue as above and save the filtrate and washings to test for calcium. To the residue on the filter add a few drops of hydro- chloric acid, and to the liquid that passes through add a drop of potassium sulpho-cyanate solution. A red color proves iron. Heat to boiling the filtrate saved to test for calcium and add 5 c.c. am- monium oxalate solution. A milky white precipitate shows calcium in the ash. Filter and wash as above and divide the filtrate and wash- ings into two parts. To one part add slowly drop by drop 5 c.c. sodium phosphate solution. Add 5 c.c. strong ammonia. A white precipitate forming on standing (immediately if there is much magnesium) proves magnesium a constituent of the plant ash. Place the remain- ing half of the above solution in an evaporating dish. Evaporate to dryness and heat to a dull redness if possible, or till white vapors no 8 longer come off. Cool and add to the residue a drop or two of hydro- chloric acid. Heat a platinum wire in a colorless gas flame till it gives no yellow color to the flame. Dip the wire into the residue and again heat it in the colorless flame. A bright yellow color imparted to the flame proves sodium. Repeat the above platinum wire test ob- serving it through a dark blue glass or a blue bottle that will shut out the yellow color. A violet color, visible only through the blue glass, proves potassium to be in the ash. To a fresh portion of about half a gram of plant ash add 5 c.c. each of distilled water and strong nitric acid. Heat to boiling, add 10 c.c. more of distilled water and filter. Divide the filtrate into three parts. To one part add 2 c.c. silver nitrate solution. A white pre- cipitate, or a milkiness imparted to the solution, proves chlorine in the ash. To the second portion add 2 c.c. barium chloride solution. A white precipitate or a milkiness proves sulphur. To the last portion of the filtrate add 5 c.c. ammonium molybdate solution and heat to blood temperature. Let stand for a while and a yellow precipitate will prove phosphorus in the ash. Exercise 4. — Nitrogen in Plants. Apparatus : Hard glass test tube, and one hole rubber stopper to fit, glass and rubber tubing for delivery tube, litmus paper, burner, test tube. Mix a gram of the dried plant material from exercise one with ten grams of soda-lime. Place the mixture in a hard glass test tube about an inch in diameter. Close the tube with a one-hole rubber stopper connected with a delivery tube that dips into a test tube of distilled water in which is placed a few small pieces of red litmus paper. Ap- ply strong heat to the hard glass tube for five minutes or more. Am- monia is formed from the plant nitrogen and this passing over dis- solves in the water. If the litmus paper turns blue it is a proof that the plant contained nitrogen. Water needed for Plant Growth. Exercise one and two have shown us that a very large amount of water enters into the composition of the plant. Every ton of growing plants contains nearly 1,800 pounds of water, and the elements of water that have entered chemically into the plant tissue. But these figures represent only a small part of the water necessary for the growth and development of that amount of plant material. Exercise 5. — Transpiration of Water From the Plant. (Field Exercise.) Apparatus : A sheet of oiled paper, a half gallon fruit jar. In the field or garden select a growing plant about six inches high. Remove all surrounding vegetation within a foot, and smooth the ground around the base of the plant. Carefully arrange a sheet of oiled paper, or other waterproof fabric, about the stem of the plant to prevent any evaporation from the soil. Invert over the plant a clean, dry, wide mouthed half gallon fruit jar. If the sun is shining you will within a few minutes notice that the glass becomes blurred and that something is collecting on the inner surface. What is it? How did it get there? This experiment may be performed in the labora- tory with a potted plant if the weather is not suited to a field ex- periment. Experimenters have proven that the weight of water transpired in a season is from fifty to seventy times the weight of the growing crop. Besides the water used by and passing through the plants, a very large amount is lost by drainage and evaporation from the soil. From the above figures we can begin to realize the importance of water to Agriculture. Exercise 6. — Transpiration is Through the Leaf. Apparatus : Three wide mouth bottles, 125 c.c. capacity, of the same size and shape. Obtain several long stemmed leaves of the same size and kind. Place the stem ends of a few of the leaves into one of the bottles and the leaf ends of a like number of leaves into another, leaving the stems sticking out. Let the third bottle serve for comparison. Fill all the bottles to exactly the same height and place them side by side in a warm place. After about three hours note the difference in the water level in the three bottles. If there is no very perceptible dif- ference, wait until the next day and observe again. Explain. Why does a field covered with growing vegetation loose more water by evaporation than a fallow field, other conditions being alike? Exercise 7. — Circulation in the Plant. Apparatus: A small wide mouth bottle. Nearly fill a small wide mouth bottle or flask with water which has been colored a bright red with eosin red, or with red ink. Care- fully pull out by the roots a young plant with light colored leaves. 10 Shake it gently to remove any adhering soil and place the roots into the bottle of red solution. Set it aside for a day and then examine the plant. Explain what has taken place. How does the plant get its water? Plant food in the soil to be available for plant use must be soluble in water. How does it get into the plant? Exercise 8. — Sunlight and the Plant. (Field Exercise.) Apparatus : A tight wooden box. In the field or garden select two like plants growing a few feet apart. Invert over one a tight wooden box, large enough to give room for the plant to grow, being careful to block it up a little from the ground to allow circulation of the air. Every two or three days ob- serve and compare the two plants until a decided difference in the color of the leaves is shown. How do you account for the difference? In the pasture turn over a board or stick of wood that has lain on the grass for a long time. Plow does the grass look under it? Is light necessary for plant growth? Exercise 9. — Air and the Plant. Apparatus: Two screw top half-gallon jars. Place about three inches of good soil in each of two screw top half- gallon jars. Plant three or four seeds of corn or beans in each. Place the jars in a suitable place for growth, water the soil well and leave them, giving water from time to time if necessary. "When the plants are about two inches high water both jars well again and screw the top onto one until it is air tight. Leave the other uncovered, keeping other conditions the same for both jars. Examine from time to time for a few days. Explain what has happened. Exercise 10. — How the Plant Gets Its Food. Apparatus : Small pocket lens. (a) Very carefully remove from loose, well cultivated soil several small plants. Examine the roots for hair-like growth. These are called root hairs. They are not roots but are hair-like cells that reach out through the soil and take up most of the plant food that enters from the soil, drinking it in with the water. (b) Examine the under side of several different kinds of leaves, using a pocket magnifying glass. Notice the occasional small, mouth- like openings. These are the breathing pores of the plant, and are called stomata (singular, stoma). The air is drawn in through these 11 pores and enters the active part of the leaf, which with the aid of sunshine, extracts the carbon from the carbondioxide causing it to unite with water and other foods brought up from the soil. In this manner starch is made in this little laboratory of the plant, the leaf, and from starch other plant compounds are formed. Exercise 11. — Tests for the Principal Classes of Plant Compounds. Apparatus: Knife, test tube, small wide mouth bottle with tight stopper, funnel, filter, evaporating dish. (a) Starches. — Make a few scratches in the surface of a growing leaf, make sections of a potato, a grain of corn and a bean. To these cut surfaces apply very small drops of dilute iodine solution. The purplish blue color produced is due to the action of the iodine on the starch that they contain. If any of these tests fail to give marked results, boil the substance to be tested in water, having first crushed it. Cool the water solution and test it with a drop of the iodine. A deep blue color should result. (&) Proteids. (The nitrogenous plant compounds). Cut cross sec- tions of corn, beans or peas and carefully touch the cuts with a glass rod that has just been dipped in strong nitric acid. Note the yellow color which will become more intensely yellow if the strong ammonia is applied to the acid spots. This coloration is due to the action of the reagents on the proteids in the seeds. (c) Fats. — Grind a tablespoonful of oats, corn or castor beans, or half as much flax seed. Place it in a wide mouth bottle and in a cool place away from all flames. Pour over it 15 c.c. of ether, stopper tightly, and shake occasionally for a half hour. Drain the liquid through a coarse filter into a clean evaporating dish, and let the ether evaporate spontaneously in the open air. The oily residue is the plant fat (oil). Seeds, The life object of the plant is to reproduce its kind. In most farm crops this is done through the seeds. The parent plant surrenders its life in order that every bit of energy that it has stored up may be transferred to its seeds, the embryos of the next generation of plants. We will now consider the conditions necessary to transform the inert seed into the active, growing plant. This pro- cess is called germination. 12 Exercise 12. — Conditions Necessary for Germination. Apparatus: Six tomato cans. Number the cans from one to six. Fill numbers one, four and six with rich, moist loamy soil. Fill number three with the same kind of soil, having first thoroughly air-dried it. Leave numbers two and five without soil. Plant in each of the soil-filled cans six seeds of peas, or beans, to a depth of one inch, and press the soil firmly around the seed. Place the same number of seed loose in numbers two and five. Numbers one, two, four and six are to be kept moist throughout the experiment. Fill number five with water, that has been previously boiled and cooled, to keep out air. Place numbers one, two, three, and five in a warm, light place. Place number six in a warm place but cover it with dark cloth or paper to exclude the light. Keep number three in a refrigerator or ice box so that the temperature may be maintained near the freezing point. Examine the cans after two or three days, and then every day until you can answer the following: Which of these conditions ; soil, moisture, warmth, air, light, are nec- essary for the germination of seeds? Seeds contain a very small amount of air. The water may also contain a small amount of air. Take this into account in answering the questions. Exercise 13. — Plump and Shrunken Seeds. Apparatus: A shallow box approximately a foot wide and two feet long. From a sample of seed wheat select 100 plump grains and also 100 grains that are much shrunken. Fill the box with a good rich loamy soil. Divide the box in the middle and plant the plump seeds in one end and the shrunken in the other. Keep the soil moist and warm. Examine the young plants from time to time as they ger- minate and grow. How many plants did you get from the plump seeds? How many from the shrunken? Let the plants continue to grow till they are nearly mature. Can you detect any difference in the hardiness of the plants and the amount of plant material produced by the two grades of seed? Exercise 14. — Seed Testing. Apparatus: Balance and weights, blotting paper, granite ware plate. (a) Purity. — Thoroughly mix the sample to be tested and weigh out 100 grams of the seed taken fairly from the whole sample. Care- 13 fully separate the weighed sample into the following parts: (1) Pure seed. (2) Weed seeds. (3) Inert matter-dirt, broken seed, straw, etc. Weigh each part. The weight of each part in grams is equivalent to its percent in the original sample. The percentage of pure seed is called the purity of the sample. Examine the weed seed to see if you can recognize any of them. Try to learn if any of them are the seeds of pests. Even a few pest seeds would be enough to condemn the sample. (&) Germination Test. — Fit a piece of blotting paper to the inside of a granite ware pie pan, or an ordinary soup plate, moisten it with all the w r ater that it can absorb. Count out 100 of the pure seeds ob- tained in (a). Distribute them well over the blotter in the plate and cover them with another moistened blotter. Invert over all a plate of the same size as the first, and place in a warm place. After about two days begin to examine the test occasionally. Each time remove the seeds that have sprouted and count and record their number. When all have sprouted that will, the total number of seeds germin- ated represents the percent of germination. The percent of germina- tion multiplied by the percent of purity gives the percent of good seed in the sample. In this manner test samples of alfalfa, wheat, beans, or other seeds that are used in your locality. Seeds shipped from other localities are liable to carry noxious weeds that will be introduced and prove a pest in your community. Examine the fields of the locality. How many pest weeds do you find? Make inquiry from the farmers to learn which are native and which are imported. Exercise 15. — The Effect that Packing the Soil Has on Seed Ger- mination. (Field Exercise.) Apparatus: Garden tools. Prepare a plat about six feet square in a rich, moist garden. Plant across it four rows of radish or other garden seed. Carefully firm the soil over two of the rows by treading on them, heel to toe, for the full length. Leave the other two rows covered loosely. Watch the plat from day to day to see which rows first appear. Where the soil is compressed it is giving up its moisture over the entire surface of the seed. The loose soil does not touch nearly the whole surface of the seed. How does moisture effect seeds (Ex. 12) ? Do not water the plat while the test is being carried on. 14 Exercise 16. — Depth of Germination. Apparatus: Three half-gallon fruit jars, three pint fruit jars. (a) Large Seeds. — Place about V/ 2 inches of good moist soil in the bottom of each of the half-gallon jars. Plant one with peas, one with beans, and one with corn, as follows : Plant two seeds near together against the wall of the jar and on the surface of the soil. Add an inch of soil, press it down gently and after turning the jar slightly to one side plant two more seeds so that they will not be directly over those already planted. Continue to add soil and plant seeds every inch up the side of the jar till near the top. Wrap each jar in dark cloth or paper to exclude the light, and set in a warm place. From day to day remove the wrapping from the jars and note the growth, recovering them immediately. This exercise should give some idea of the power of different kinds of seeds to force their plantlets up through the soil. Note the depth of the lowest seed in each jar that is able to penetrate to the surface. (b) Small seeds. — Repeat (a) using pint jars and planting the lowest seeds about an inch from the bottoms. Use small seeds, such as radish, alfalfa, clover. How do the depths of germination with large and small seeds compare? Give a reason for this. Oil producing seeds contain much more food in proportion to their size than do the starchy seeds. THE SOIL AND ITS RELATION TO THE PLANT. The soil is that outer layer of the earth's surface that serves as a home for plants. The harder part of the soil underneath the culti- vated layer is called the subsoil, to distinguish it from the surface, or true, soil. Throughout a large area of the great valleys and plains of California there is no well marked subsoil, the characteristics of the soil changing very little from the surface downward for many feet. This peculiarity allows great tracts to be graded for irrigation without bringing to the surface a "raw" subsoil. In humid regions the surface soil is rarely more than a few inches deep, and if the sub- soil is brought to the surface in more than small amounts it is quite detrimental to crops till it has had time to weather and become like the surface soil. 15 Exercise 17. — Soil and Subsoil. (Field Exercise). Apparatus : Spade. Go to some nearby field that has a clay or clay loam soil. Dig a hole two or three feet deep, carefully smoothing one side with a spade. Distinguish between the soil and the subsoil and note the character- istics of each. Also find a sandy soil and dig as above described. Do you find the same marked division as in the clay soil? Scientists tell us that at one time the surface of the earth was en- tirely made up of rocks. Through many ages these rocks have been gradually pulverized and powdered by many natural agencies, chief of which are water, ice, heat and cold, and wind. Exercise 18. — Rock Powder. Apparatus : Hammer and anvil or heavy piece of flat iron. Get a piece of clean rock material and powder it with a hammer on an anvil or piece of iron. Collect the powder and compare it with handfuls of different kinds of soils. How does it differ from the soils? Examine the rocks in the neighborhood and see if you can discover any evidence of their breaking down into rock powder. But, as you will have observed, rock powder differs from good soil. We can not grow a crop of beans, wheat or alfalfa on a soil made up of rock powder. Devise an experiment to prove this. Exercise 19. — Plant Growth on Bock Surfaces. (Field Exercise). Go to some nearby place where there are large rocks or rocky cliffs and examine their surfaces carefully to see if you can find any plant growth on them. If you search long enough you will no doubt find very minute mosses or lichens growing there. These are able to extract their very small amount of mineral food from the solid rock. As the surface of rocks begins to powder, low forms of plant life find a home upon them. After living their simple life they die and their decaying bodies are mingled with the powdered rock. After a time the very poor soil formed in this way is able to support a plant that is a little higher up in the scale of life, and this plant in its turn adds its quota of decaying material to the slowly forming soil. And so the process continues till the powder has been changed to a true soil that is rich enough to support the life of the higher plants. Bur- rowing animals, earth worms and insects have also aided materially in soil formation, and their bodies have added to the decaying mat- 16 ter supplied by the plants. This decaying organic matter which mixes with rock powder to form the true soil is called humus and is one of the most essential constituents. Exercise 20. — Humus in Soils. Apparatus : Two large test tubes. Place in a large test tube 10 c.c. of a 10% solution of caustic soda (NaOH) or caustic potash (KOH) and add about two grams of a dry rich soil. Carefully heat to boiling and set aside till the soil set- tles. Note the dark color of the solution. The coloration is due to the humus in the soil sample. Repeat the test using a very poor sandy soil. Note the difference in the color of the two solutions. With a little experience in its use, one has in this test a very good index to the amount of humus in a soil. Beside the rock powder and organic matter that we have been studying — dead matter — the soil is full of very active life. With the eye we can discover nothing more than the parts that are inanimate. But the high power microscope reveals an innumerable host of minute organisms called bacteria. They are of many kinds. While some are detrimental, most of them are numbered with the farmer's best friends. We will have occasion to mention some of these in connec- tion with the study of nitrogen in the soil. The rock powder, or mineral part of the soil, is made up of differ- ent sized particles and these according to their diameters, are classi- fied from the largest to the smallest, as sand, silt and clay. The value of soils is affected quite materially by a variation in the amount of these constituents. Exercise 21. — Sand, Silt and Clay in Soils. Apparatus : Balance and weights, mortar, rubber pestle, tall beaker of about 600 c.c capacity, flask with a long, narrow neck. Weigh out about 25 grams of an air dry sample of loamy soil, and place it in a mortar. Add about 15 c.c. water and rub well with a rubber pestle. (This may be made by fitting a stirring rod into a one- hole rubber stopper) . Let it settle for a minute and carefully pour off the muddy water into a tall beaker of 500 or 600 c.c. capacity. Add more water to the mortar and repeat the operation till the water in the mortar no longer gets muddy. The part remaining in the mortar is coarse sand. With small amounts of water wash the sand from the mortar through a funnel into a flask with a long neck (not over a half inch inside diameter.) 17 Add water to the beaker containing the muddy material till it is nearly filled. Stir thoroughly and then let it stand without being dis- turbed for one hour. The muddy appearance of the water is due to the clay, which does not settle. Carefully siphon off the muddy water without disturbing the sediment. Fill the beaker again with water, stir it, let it settle for an hour and siphon as before. Repeat this oper- ation till on standing an hour the water above the sediment is clear, showing the absence of clay. Transfer the sediment to the flask con- taining the sand. Nearly fill the flask with water and stopper it well. Shake it thoroughly and invert it in a funnel rack or ring stand so that the neck hangs perpendicular. Let the soil particles settle and note the different layers ranging from the coarse sand at the bottom of the neck to the fine silt at the upper part. If care is used in weigh- ing out the sample this gives an approximately accurate way of esti- mating the percents of sand, silt and clay in a soil. To get the percent of clay the siphoned clay water must be made up to a known volume and an aliquot portion be evaporated to dryness and weighed in a dish of known weight. After this calculation is made the remaining part of 100 % is divided between the sand and silt in proportion to the depths of each in the flask neck. Rocks and Minerals. Rocks are generally made up of two or more kinds of simpler sub- stances known as minerals. Minerals are more or less pure natural chemical compounds. A few rock masses such as limestone and gypsum are made up of one kind of mineral. Soils are formed by the breaking down of rocks into minerals, and in some cases the changing of the minerals by chemical action into other compounds. Such a breaking down process is called weathering. Below we will discuss briefly some of the common minerals that make up the soil. For a fuller description refer to a mineralogy, or better, to some complete treatise on soils, such as that of Dr. Hilgard. Quartz, silicon dioxide, is one of the most abundant minerals and hence is found largely in soils. It contains no plant food but is a very valuable soil former on account of the effect it has on the physical properties of the soil. The sand of humid regions is made up almost wholly of quartz fragments. The sands of the semi-arid regions of the West contain, besides quartz, a very high percentage of fragments of other minerals, many of which are rich in plant food. The addition of water and humus to these arid sands renders much of this food easily available to plants, hence the great richness of the soils on 18 many of the western plains recently opened to cultivation by the great irrigation projects of the government. Feldspar is also a very abundant mineral. Weathering breaks it up into clay, compounds of potash and lime which are very valuable plant foods, and small amounts of other substances. On account of the potash and clay, feldspar is the most valuable soil mineral. There are several varieties of feldspar. The one richest in potash is called orthoclase. Mica, a somewhat common, bright, scale like mineral, is often called "isinglass." Though it contains considerable potash, it is not a very valuable soil former because it weathers very slowly. The bright shining particles in sand are usually fragments of mica. Homblend is the name given to a group of dark colored minerals that enter frequently into soil formation. The most common one is black, and as it weathers forms a reddish colored clayey soil. The red color is due to the iron that the mineral contains. Hornblend contains very little plant food, but the clay and iron that it adds to the soil aid materially in improving physical conditions. Serpentine is a greenish colored mineral that weathers very slowly, and contains little or no plant food. It contains magnesium, which is required in very small quantities for plant growth, but the large amount left in the soil by the weathering of this mineral and others closely related to it, is harmful to many plants. Large amounts of lime in the soil seem to overcome the evil effect of the magnesium. The rocks of the California Coast range contain considerable serpen- tine and related minerals. Talc, "soapstone, " is closely related to serpentine. Limestone is carbonate of calcium. It is found in all soils and is not only valuable for the plant food that it contains, but has a very marked beneficial effect on the physical properties of the soil. When it occurs in large masses it is mined and burned to produce the ' ' lime ' ' of commerce. Gypsum is a sulfate of calcium. It is even more valuable than limestone as a soil maker. It is slightly soluble in water and hence is very easily available to the plant. Besides its use as a plant food and its good effect on the physical condition of the soil, it is used extensively as a remedy for "black alkali." It is mined extensively and ground and sold as "land plaster." When properly burned it is "plaster paris." 19 Apatite and Phosphorite are minerals containing large amounts of phosphate of lime. This compound is found in minute quantities in all soils. Where these minerals are found in large amounts they are mined and prepared into phosphate fertilizers. They are very im- portant constituents of the soil. Exercise 22. — Soil Minerals. Examine the minerals in the school collection and learn which are valuable soil formers and why. Search your reference books to learn what you can of these minerals. Exercise 23. — Local Minerals. (Field Exercise.) Examine the rocks and minerals of the vicinity. Make a collection of those that seem to enter into the formation of the soil. Try to identify these minerals and then look up their chemical composition. Does this aid you in gaining a knowledge of the soils of your locality? Alkali. The minerals thus far mentioned are all insoluble in water, or nearly so. There is another class that is very readily soluble. Many of them are formed by the weathering of other minerals. In the humid climates these soluble minerals are washed away in the drain- age of the country. In arid climates they remain in the soil and are called collectively "alkali." The three principal alkali minerals are sodium chloride and sodium sulphate, which are known as "white alkali," and sodium carbonate, called "black alkali." ~Etxercise 24. — Alkali. Apparatus : Three tomato cans, three small pans, funnel, oil cloth, filter paper, three small evaporating dishes, stirring rod. Melt the tops from the cans, being careful not to cause them to leak. Get enough clay-loam soil to fill the cans and divide it into three parts. Put one part untreated into the first can. Place the other two parts on pieces of oil cloth. To one part add 15 grams of finely powdered soda crystals (sodium carbonate, Na 2 C0 3 ), mix thor- oughly and place in the second can. To the other portion add 5 grams each of common salt (sodium chloride NaCl) and Glauber's salt (sodium sulphate Na 2 S0 4 ), finely powdered. Mix thoroughly and place in the third can. Add enough water to each can to saturate the soil. When the water has settled compact the surfaces of the soil in the cans so that it is quite hard. Place the cans in a warm place for 20 two or three days and watch for results. The first can serves as a check. What difference in the appearance of the surface of the soil in the three cans? Sodium carbonate, though white, acts chemically with the humus in the soil, forming a black substance which, as the water evaporates, is left on the surface of the soil as a dark colored excresence; hence the name, " black alkali." The chemicals in the third can do not act on the humus, and hence come to the surface white. Again thoroughly wet the soils, adding only a little water at a time so that the alkali may be washed down into the soil as it dis- solves. Beginning as soon as the soils are in condition to work, culti- vate the cans to the depth of an inch every day for a week. Why does not the alkali come to the surface again? Perforate the bottoms of the cans with a nail. Place each in a separate pan and add water a little at a time until about a pint of drain water is collected from each can. Again pack the soil surface and place the cans in a warm place for two or three days. Filter about 100 c.c. portions of each of the drainage waters into separate evaporating dishes and evaporate to dryness. Is there as much residue in the first sample as in the second or third? With a stirring rod taste the first residue. Add a few drops of dilute hydrochloric acid (HC1) to the second residue. An effervescence (frothing) shows car- bonates present. Try the first residue in the same way. Is the result the same? Taste the third residue. Is it salty? Does it taste like the first? Have the alkalies been washed from the soil? After the cans have stood for two or three days again examine their surfaces. Do they show alkali as before? Draw conclusions from this exercise as to the nature of alkali and methods of ridding the land of it. Exercise 25. — Gypsum Treatment for Black Alkali. Apparatus : A tomato can. Prepare a can of the same kind of soil as in the last experiment. Weigh out 15 grams each of soda crystals and gypsum (land plaster) T powder each thoroughly and mix them with the soil before placing it in the can, add water to the soil slowly till it is saturated. Compact as in the last experiment. Place in a warm place for two days and note the incrustation. Is it " black alkali ' ' or has the gypsum changed it? How does the residue compare with that in the third can in the last experiment? If the materials have been well mixed the sodium carbonate will have acted with the calcium sulphate (gypsum) and formed insoluble calcium carbonate (limestone) and sodium sulfate, one of the compounds in "white alkali." In this manner the very 21 harmful ''black alkali" can be changed to much less dangerous white variety. Besides containing harmful minerals, most alkali soils are rich in soluble plant food, such as nitrates and potassium compounds. Learn all that you can about the reclamation of alkali lands. Consult Dr. Hilgard's "Soils" and the publications of the California Experi- ment Station, which furnish valuable references on this subject. Exercise 26. — Local Alkali Lands. (Field Exercise.) Visit the localities near your school where alkali is found. Make inquiry of the farmers to learn what has been done to better the con- ditions. Compare the efficiency of different methods. Learn if irri- gation has had any part in causing the land to become "alkalied. " Write a short article on "How to improve Alkali Lands," basing your statements on your observations and reading. Acid Soils. Not only do we have alkali lands, but in some localities may be found soils that are decidedly acid. They are commonly spoken of as "sour" soils. Many varieties of plants will not grow on these lands, and the beneficial bacteria, such as the nitrate producers, can- not thrive in them till the sourness is removed. The soils most commonly found to be acid are : those that are very rich in humus producing matter, such as boggy marsh land and tule land ; poorly drained clay soils ; and soils that have been treated with large amounts of acid producing fertilizers. Drainage will generally remove the causes of acidity. Lime and wood ashes are the best chemical remedies for sour soils. They improve it by neutralizing the acids. Acid soils are not very common in California. Exercise 27. — Alkali and Acid Soil Tests. Apparatus : Three small dishes, red and blue litmus paper. Select two or three samples of soils from alkali spots. Also get samples from boggy soils and from poorly drained heavy clay soils. Place small handfuls of each of these samples in separate pans or dishes. Insert in each sample small strips of red and of blue litmus paper. Moisten with distilled water and press the soils down firmly about the papers. Let them stand for an hour or more. Carefully remove the papers from the soil, wash them thoroughly with distilled water and dry them in a room that is free from laboratory gases. Examine them when dry and compare their colors with the original paper. "Black alkali" will turn the red litmus to blue, and acids will turn the blue to red. 22 HOW PLANTS GET NITBOGEN. Nitrogen is obtained by the plant from compounds found in the soil. Unlike the other elements that the plant extracts from the soil, it is not a constituent of rocks, and hence is not produced for the plant by rock weathering. It comes indirectly from the air. The principal sources of nitrogen plant food are two. First, all animal or vegetable matter contains more or less of the element combined with other ele- ments in the formation of the tissues. As this matter decays certain classes of bacteria act upon it and along with many other changes, the nitrogen is passed through a series of changes till it forms nitrates which are easily available for plant food. Second, a class of bacteria entirely independent of those mentioned in the first part, make their home on the roots of certain plants and are able to change the free nitrogen of the air to nitrates which are used or stored by the plant on which the bacteria make their home. Exercise 28. — Nitrogen Nodules. (Field Exercise.) Go into the fields and pastures and carefully dig without injury to the roots (this may be accomplished more easily when the soil is quite wet) a specimen or two of each of as many of the following plants as you can find: field pea, sweet pea, field bean, soy bean, horse bean, lupine, alfalfa, burr clover, red clover, white clover, vetch. Examine the roots for very small potato-like knots. These plants all belong to the same botanical family, ' ' leguminosae, " and are called commonly legumes. They are distinguished from other plants by their blossoms, which are all "butterfly shaped," having a keel and wings ; though the blossoms of some, as the clovers, are so small that they hardly show the form without being very closely examined. Ex- amine the roots of wheat, oats, barley or corn for knots like those found on the legumes. Do you find any? The knots, or "nodules" as they are called, are the home of the bacteria. In some way these minute organisms are able to use the free nitrogen of the soil air and combine it with the mineral matter of the soil to form nitrates. The plant cannot use the free nitrogen but flourishes on the nitrates, which the bacteria offer as rental for the home provided by the legume. The plant satisfies its needs from the nitrates thus produced and any excess remains in the soil for a future crop. This suggests a reason for the crop rotation practice of following a legume crop (a nitrogen food producer) by a cereal crop (a nitrogen food consumer). Nitrogen is by far the most expensive plant food to buy in the form of fertilizers, so any cropping practice 23 that will add it to the soil without additional cost should be followed by the farmer. Some leguminous crop should form a part of every system of rotation. Make a study of the crops of your locality and see what legumes are the best and most profitable producers. CLASSIFICATION OF SOILS. Soils are divided into two classes according to their location with respect to the rocks from which they are derived. Sedentary soils are those that are formed directly over the parent rock. They are also called residual soils, and ' ' soils in place. ' ' They partake of the char- acteristics of the underlying rocks. Transported soils are those that have been moved some distance from the rock that gave them origin. They are sub-named according to the method of their removal from the original source. Colluvial soils are formed by the soil and dis- integrated rock masses sliding and washing down a hillside and lodg- ing at its base. Though changed slightly by washing, they partake largely of the nature of the rocks from which they slid. Alluvial soils are formed by the deposits of streams. They form the valley lands, and are made up of the materials gathered all along the course of the stream. They partake of the characteristics of the rocks of the entire drainage area from which they are derived, but are much modified by the velocity of the water and the amount of weathering that has taken place. Drift soils are those deposited by the melting of glaciers. Aeolian soils are those that have been carried and deposited by the wind. Experiment 29. — Classifying Local Soils According to Location. (Field Exercise.) Sketch a map of your locality, showing the different kinds of soil formations according to the above method of naming. Give your rea- sons for so naming each kind. Dig into each kind of soil and study the shape and nature of the rock fragments. Are there any aeolian or drift soils in the vicinity? Exercise 30. — Sampling Soils. (Field Exercise.) Apparatus : Spade, pail, oil-cloth. Select a spot for sampling and carefully remove from the surface all stones, stubble, and other matter not belonging to the soil. Dig into the cleared space a V-shaped hole with one side of the V perpen- dicular, and a little wider than the spade. On the perpendicular side, measure the depth to the change in color, which indicates the division 24 between the soil and subsoil. Carefully clear out all the loose soil from the hole. With the spade shave thin slices from the perpendicu- lar side, collecting the soil in a pail till you have about a quart of the sample. In the same manner take samples of like amount from other parts of the field, placing them in the same pail as the first. Pour all the soil thus collected onto a piece of oil-cloth and mix it thoroughly. Save about a half gallon of the mixture for the sample of the field. If there are two or more distinct kinds of soil in a field, sample each of them and keep the samples separate. If there is no marked line between the soil and the subsoil, sample to the depth of one foot. The subsoil may be sampled in the same manner as the surface soil. Care must be taken to remove all loose soil from the hole before commencing to collect the subsoil sample. Soils may be sampled to a greater depth with an old wood augur that cuts about a two-inch hole. Have the blacksmith fasten a half inch pipe coupling to the head of the bit. Cut and thread three pieces of pipe each about eighteen inches long, for extensions to the shank of the augur. Use a half -inch "tee" with a piece of pipe about a foot long screwed into each side, for a handle. In sampling the soil, draw the augur at each foot in depth and place the borings in separate cans or pails. Soil Moisture, On a previous page it was mentioned that the soil was made up of rock powder and humus, and that it contained a multitude of living organisms, bacteria. The soil also contains air and water, and its value as a crop producer is materially effected by the relative amounts of these two constituents. Exercise 31. — Moisture in the Soil. Apparatus : Spade, oil-cloth, screw-top jar, balance and weights, oven and thermometer, small weighing pan. Collect a sample of soil as directed under the sampling of soils. Cover it at once to prevent any evaporation. Carry to the laboratory and weigh the sample as soon as possible. Carefully spread it on a piece of oil cloth and place it in a dry room where it will not be dis- turbed. After two or three days weigh the sample, expose to the air again and the next day weigh the sample again. Continue this until there is no longer a loss in weight. Record the total loss and calculate the percent of moisture lost. But this is not all the water that the soil contains. Each particle is yet covered with a very thin film, called "hygroscopic moisture" — the part that cannot evaporate at the 25 ordinary temperature. The soil is now said to be "air-dry." De- termine the percent of hygroscopic moisture in the air dry sample obtained, by the same method that you determined the moisture in the plant, Exercise 1, using a temperature from 100° to 105° C. Exercise 32. — Collecting Local Soils. (Field Exercise.) Apparatus: Spade, collecting pails, bottles or jars for preserving samples. Collect samples of soil from the neighborhood, getting as many varieties as possible, from coarse sandy soils at one extreme to heavy clay soils at the other. Spread the samples on old newspapers in a dry place till they air-dry, then set them away in wide mouth bottles or jars, properly labeled as to locality, and save them for future use. Exercise 33. — Water Holding Capacity of the Soil. Apparatus : Balance and weights, three funnels, niters, 50 c.c. graduated cylinder. Use three funnels of a diameter of about four inches. Fit a filter to each funnel and moisten each with water and let drain till water no longer drips from the funnel. Weigh out 50 gram samples each of air-dry heavy clay, loamy, and coarse sandy soils. Place the weighed samples each in one of the prepared funnels. Place a beaker under each funnel. Add slowly to each, 50 c.c. water and let them drain till water no longer drips from the funnels. Measure the number of cubic centimeters of water that drains from each sample. Subtract these amounts from the 50 c.c. used and the difference will be the water absorbed by the sample. As a cubic centimeter of water weighs a gram, the c.c.s absorbed multiplied by 2 will give the grams of water absorbed by 100 grams of soil, or the water holding capacity expressed in percent. How do the results compare for the three kinds of soil used. Exercise 34. — The Effect of Organic Matter on Water Holding Capacity. Apparatus : Balance and weights, funnel, filter, graduated cylinder. Mix together thoroughly 40 grams of air-dry coarse sandy soil and ten grams of fine air-dry leaf mold or well rotted stable manure. In the same way prepare a sample of the air-dry heavy clay loam, 40 grams, and 10 grams of the manure or leaf mold. Determine the water holding capacity of these prepared samples as you did the soils 26 in the last exercise. Tabulate the results of the two exercises and draw your conclusions as to the effect of manures on the power of a soil to absorb moisture. Exercise 35. — Size of Particles and Water Holding Capacity. Apparatus : Balance and weights, hammer. Weigh accurately a large smooth pebble about one and one-half inches in diameter. Dip it into water, remove it and immediately weigh again. Calculate the ratio of the weight of the adhering water to that of the pebble. Dry the pebble and with a hammer carefully break it into five or six good sized pieces. Weigh these pieces that any loss of small particles may be accounted for, and dip each into water and remove and weigh as above. Calculate the ratio of the weight of the total amount of water adhering to pieces to that of the combined weight of the pieces. How does this ratio compare with the first one? The surface in the second case has been increased by the total amount of broken area, which is added to the area of the un- broken pebble. Diminishing the size of the particles in a given weight of soil, then, increases the surface. Which has the greater water hold- ing capacity in proportion to weight, a coarse soil or a fine one? Is this conclusion born out by your experience with sandy and clay soils in the previous exercises? Exercise 36. — Capillarity. Apparatus : Two wide mouth bottles, 250 c.c, 2 wide mouth bottles, 60 c.c, balance and weights, lamp wick. Use two wide mouth bottles of equal size, capacity about 250 c.c. Place the bottles side by side and fill one of them two-thirds full of water. Thoroughly wet a lamp wick and place it so that one end dips about an inch into water and the other end hangs in the empty bottle. Let it stand for about an hour. Make a drawing of the apparatus. The water rises through the wick by the process known as "capillar- ity. ' ' What causes the oil to rise in the wick of a kerosene lamp ? Into a small wide mouth bottle (60 c.c.) pour kerosene till it stands about three-fourths of an inch deep. Fill the bottle with finely powdered air-dry soil, and press down the surface with the fingers. Let it stand for about 15 minutes. Does the kerosene rise through the soil? Apply a lighted match to the surface of the soil. Explain what has taken place. Repeat the second part of the experiment, using water instead of 27 the kerosene. After the moisture reaches the surface weigh the bottle and set it away in a warm place until the next laboratory period. Weigh the bottle again. Explain any change in weight. Exercise 37. — Soil Capillarity. Apparatus : Granite ware pan, capillary tubes. (a) Use a granite ware pan about 10 by 12 inches in size, or an ordinary tin milk pan may be used. Pour good loamy soil, air-dry, into the middle of the pan till a sharp mound stands several inches high, without rising on the sides of the pan. Carefully pour water around the inside edge of the pan till it stands nearly two inches deep. Watch the mound of soil and explain what takes place. Does this show in any way how the higher parts of a field may get water for plant growth ? Why is it that some creek and river bottom lands grow excellent crops of alfalfa without irrigation? ( o ) Place the ends of several sizes of capillary tubing into a bottle of water colored with ink. How does the rise of the water in the tubes relate to their diameters? The soil is full of very minute, though very crooked tubes. They are formed by the spaces between the soil particles, and it is through these tube-like spaces that the water rises. Exercise 38. — Porosity of Soil. Apparatus : Graduate cylinder, wide mouth bottle 250 c.c, a stiff wire. Measure the water, to the nearest cubic centimeter, necessary to fill a wide mouth bottle, of about 250 c.c. capacity, to the neck. Pill the bottle to the neck with an air-dry sandy soil. From a vessel con- taining a measured quantity of water, pour slowly into the bottle. Stir the soil gently with a stiff wire, if necessary, to allow the water to penetrate to the bottom and the air to escape. When the soil is thor- oughly saturated with water to the neck of the bottle, measure the amount remaining in the vessel. The amount of water used to satu- rate the soil equals the volume of pore space that it contains. Volume of water used divided by the volume of the soil and multiplied by 100 will give the porosity expressed in percent of the volume. Under natural conditions in the field the pore space is filled partly with air and partly with water. With ordinary soils the condition best suited to crop growth is when the pore space is about half filled with air and half with water. 28 Exercise 39. — Shrinkage of Clays. Apparatus : Three can lids, a small pan for mixing soils. Mix a handful of clay soil with a little water and mix into a stiff dough, being careful to have it thoroughly wetted all the way through. Make a similar dough of the clay soil mixed with about one-third as much leaf mold or other well rotted organic matter. Prepare a third sample from a sandy soil. Pack each of these samples into a small bak- ing powder can lid, or similar container, and set them away in a warm dry place till the next laboratory period and then examine them for shrinkage and cracks. What do you find ? Do you find similar results in the fields after a period of dry weather? Exercise 40. — The Effect of Color on Soil Temperature. (Field Exercise.) Apparatus : Two thermometers, hoe, ruler. Select a smooth, open space in the field, away from any shade. The day must be warm and sunny. Clear the surface of the soil of any stubble or rubbish for a space about four feet square. Within this cleared space lay off two eighteen-inch circles and cover one to the depth of about 14 inch with lamp black, and the other to the same depth with whiting or other powdered white material. Insert the bulb of a thermometer into the soil in the center of each circle to the depth of an inch. Examine and record the temperature of each every five minutes for at least half an hour, or until there is a decided difference. What effect does color seem to have on the temperature of the soil, other conditions remaining the same? Exercise 41. — The Effect of Evaporation on Soil Temperature. Apparatus : Four tomato cans, 4 thermometers, plotting paper. Fill two tomato cans with air-dry clay soil and two with air-dry sandy soil. Moisten well one can each of the clay soil and the sandy soil. Bury the four cans side by side in dry soil in a sunny spot in the field, leaving about half an inch of the tops above the surface. In- sert a thermometer in each to the depth of an inch, and read and re- cord the temperature about every hour throughout the day, noting the time of each reading. On plotting paper draw a curve of tempera- tures for each can, using Time and Temperature for the co-ordinates. Use different colored inks or pencils to represent the curves of the four samples. If the first day of the experiment does not show decided 29 results continue the readings through the second day. What is your conclusion as to the effect of evaporation on soil temperature? Which shows the greater changes, the moist clay or the moist sand? Why? Exercise 42. — Effect of Mulches and Cultivation on Evaporation. (Field Exercise.) Apparatus: Described in body of the exercise. Remove the tops from eight good five-gallon coal oil cans, by cut- ting around the top just inside the rim. Hammer the ragged edge down smoothly against the sides of the can. Fill each to the depth of an inch with fine gravel. Place in a corner of each can a piece of half-inch water pipe long enough to reach to just above the edge of the can. Fill the cans all alike with soil to within two inches of the tops, gently jolting the cans on the ground as you fill them to compact the soil. Number the cans from one to eight. Cover the soil in number six with a mulch of one inch of coarse sand. Cover number seven with a mulch of an inch of finely cut dry straw. Cover number eight with a mulch of an inch of fine stable manure. Weigh each can and record the weights. Select an open place in a lot or field that will be free from disturbance and bury the cans in the ground till the sur- faces inside and out are on the same level. Place them in a row about two feet apart, arranging them according to their numbers. Pour through a funnel a measured quantity of water into the pipe in each can, adding it slowly so that the soil will have plenty of time to take it up. Keep adding the water till the cans without a mulch begin to show a little dampness at the top. Make the quantity the same added to each can. During the experiment leave the surfaces of numbers 1, 6, 7, and 8 undisturbed. Cultivate the others carefully once each week with a small garden tool, or a sharp stick, as follows : Number two, one inch deep. Number three, two inches deep. Number four, three inches deep. Number five, four inches deep. Continue the experiment for from six to ten weeks, adding meas- ured quantities of water to the cans as they need it to keep them in good condition for crop growth. Keep a record of the amount of water added to each can. After there seems to be a considerable difference in the amounts of water taken up by the soils in the various cans, carefully dig them up and remove the soil adhering to the out- sides of the cans. Wipe each can clean with a cloth and weigh and record the weight. Add to the original weight of each can of soil the 30 weight of the water added to it, and subtract from the result the last weight of the can. The difference represents the weight of water evaporated. Any rainfall during the time of the experiment must be taken into account in making the above calculations. Tabulate your results and draw conclusions as to the effectiveness of the mulches and the different depths of cultivation in retaining the moisture in soils. Exercise 43. — Windbreaks and Soil Moisture. (Field Exercise.) Apparatus: Same as for soil sampling and determining moisture. Select a good size field that is protected by a wind break of trees. The conditions of soil, cultivation and cropping should be the same over the part of the field studied. On the side from which the prevail- ing wind blows, with a soil augur take first and second foot samples at thirty feet from the hedge, and at every 100 feet from there out till you have sampled five or more places. Seal and label the samples obtained and take them to the laboratory and determine the percent of moisture in each sample by the method used in exercise 30. What are your conclusions as to the effect of windbreaks in retaining soil moisture? Fertilizers. Exercise 44. — Fertilizers. (Field Exercise.) Let the students collect small samples of the various fertilizers used in the locality, procuring if possible from the farmers the guar- antee label that goes with each fertilizer. Make a study of each sample and describe it. Test each with litmus paper and try to determine what causes the acidity or alkalinity of the samples that show a test. Exercise £5. — The Absorption of Manure by the Soil. Apparatus : A pan, a tall quart can, a large funnel, a beaker. Soak a quart of well rotted stable manure for two days in enough water to cover it. Perforate the bottom of a tall narrow can, holding about a quart, and fill it with dry soil. Set it in a large funnel. Pour off the water from the manure and note its color. A large part of the fertilizing value of the manure has dissolved in the water. This sug- gests that the practice of piling manure in heaps and letting it lay exposed to the leaching action of the winter rains is a very wasteful one. Slowly pour the manure water over the soil and let it drain through into a beaker. Compare the color of the drainage with that 31 before adding it to the soil. Has the soil absorbed the valuable part of the manure? A common practice is to pile a load of manure in a place, throughout the field, and scatter the piles after they have rotted all winter. Will this give an even distribution of the fertilizing part of the manure ? Make a study of the best methods of saving and using barnyard manures. Make an inspection of the farms in the neighbor- hood and see if these methods are being used. The teacher will be able to give references to bulletins and other literature on the subject. Exercise 46. — Fertilizer Field Tests. This set of tests should be carried on in cooperation with some pro- gressive farmer whose farm is near the school. Select a field that is not yielding well. The part used should be level, of a uniform texture and thoroughly tilled in preparation for the seed. Lay off a square of 150 feet on a side, and measure in 4% feet from the outside all around for a walk. Running one way through the middle lay off a nine- foot walk, and perpendicular to this on each side lay off four plats each thirty-three feet wide, with three-foot walks between them. This gives eight plats each 33 by 66 feet, and containing one-twentieth of an acre, each surrounded by a walk. Draw a diagram of these plats in your note book. A scale of one centimeter to ten feet is a very con- venient one for this drawing. When the soil is thoroughly prepared, and just before seeding, apply the fertilizers by sowing them broad- cast, being careful that all parts of the plat receive the same quantity of fertilizers. The eight plats should be fertilized as follows : (Use only high grade fertilizers.) No. 1. No fertilizer, serving as a check. No. 2. 10 lbs. sulfate of potash. No. 3. 20 lbs. acid phosphate. t No. 4. 10 lbs. nitrate of soda. No. 5. 10 lbs. nitrate of soda, 20 lbs. acid phosphate. No. 6. 10 lbs. nitrate of soda, 10 lbs. sulfate of potash. No. 7. 10 lbs. sulfate of potash, 20 lbs. acid phosphate. No. 8. 10 lbs. nitrate of soda, 10 lbs. sulfate of potash, 20 lbs. acid phosphate. Sow all the plats exactly alike with the same kind of seed. One of the crops ordinarily raised in the community, such as corn, wheat, barley, etc., should be used. If the class is large enough three or four sets of plats as described above may be used, each being sowed to a different crop. The walks should be kept free from weeds and grain at all times. When the crop is ripe, each plat should be separately 32 cut and threshed and the yield of grain and straw both carefully weighed. A study of the yields of the plats as compared with the fer- tilizers applied will give the necessary data to determine what com- bination of fertilizing material will cause the field to increase its yield of that particular crop, and will give a partial check on the defi- ciency of the soil in any particular plant food. A second year of tests on the same plats will serve as a valuable check on the first year's results. Exercise 47. — Manure and Gypsum Field Tests. If the instructor so desires, plats 9 and 10 may be added to the eight used in Exercise 46, and treated as follows : No. 9. 20 lbs. land plaster (gypsum). No. 10. A half ton of stable manure. The plaster and manure should be well mixed with the soil and the plats sown and harvested as the others are. They will probably show more marked results the second year than the first. Exercise 48. — Orchard Fertilizer Tests. After making a careful study of exercise 46, let the student devise a series of tests to show the fertilizer requirements of the fruit trees in some nearby orchard. Fertilizers should not be applied around the base of the tree or much injury may be done. The feeding roots are spread over an area equal to or greater than that covered by the branches, and the fertilizer should be spread accordingly. The trees should be numbered and the results noted for two or three years. The fertilizers have little apparent effect on the trees for the first year. Exercise 49. — Crop Rotation. From the reference books and bulletins at your command make a careful study of Crop Rotation. Determine what the principal objects of rotation are, and how it is applicable to your locality. Visit the most progressive farmers and learn their system of crop rotations. "What are the crops in each rotation? How are they placed, and for what reasons ? After making the above studies, visit some farm where rotation is not practiced. Make a map of the farm and divide it into fields suitable for rotation practice. Plan a system of crops for the farm as you have mapped it. Give your reason for placing each crop in its place in the system. 33 Exercise 50. — Weeds. (Field Exercise.) Visit the farms in the neighborhood and inquire about the weeds that are giving trouble. Learn what is being done to destroy them. Make a collection of all the kinds of weeds that are proving to be pests, and learn their local names. Try to give to each its botanical name. (This will prove an excellent practice for a class in Botany). Examine the roots, seeds and other parts of each kind of weed. Draw conclusions from your observations and state why each is a pest. From your reference books learn all you can about the destruction of weeds. BEFEBENCE BOOKS. The number of excellent text books dealing with Elementary Agri- culture is increasing rapidly, so that it is possible for a school to have quite a complete library for agricultural reference, and the cost need not be great. The following will prove especially helpful as refer- ences in this series of exercises : 1. The Soil, C. W. Burkett. 2. Principles of Soil Management, Lyon and Fippin. 3. Soils, E. W. Hilgard. 4. First Principles of Soil Fertility, Vivian. 5. The Fertility of the Land, I. P. Roberts. 6. Fertilizers, E. B. Voorhees. 7. Principles of Agriculture, L. H. Bailey. 8. Agriculture for Schools of the Pacific Slope, Hilgard and Os- terhout. 9. Elements of Agriculture, G. F. Warren. 10. Practical Agriculture, J. W. Wilkinson. 11. One Hundred Experiments in Elementary Agriculture, R. 0. Johnson. 12. The Physics of Agriculture, F. H. King. For a first-class reference library covering the general subject of agriculture every school should have, if possible: 13. The Cyclopedia of American Agriculture (4 vols.), L. H. Bailey. Numbers 1 and 4 are published by the Orange- Judd Co., New York. Numbers 2, 3, 5, 6, 7, 8, 9, 12 and 13 are published by The Mac- millan Company, New York. 34 Number 10 is published by the American Book Co., New York. Number 11 is published by the author, R. 0. Johnson, Chico, Cal. The bulletins and publications of the California Experiment Sta- tion, Berkeley, and the Farmers' Bulletins of the U. S. Department of Agriculture furnish excellent references. APPARATUS. Most teachers prefer to select their own apparatus and adapt it to the experiments to be performed. The following list is only sug- gestive In most of the exercises two or more can work together and the teacher will probably find it convenient to have different sets of students working on different exercises. This will allow a wide range of work with a small amount of apparatus. FOR THE SCHOOL. One measuring tape, 25 feet ; 1 sheet iron drying oven with means of heating it to a temperature a little above the boiling point of water ; a collection of farm and garden seeds. FOR EACH TEN STUDENTS IN CLASS: One spade ; 1 hammer ; 2 hoes ; 2 rakes ; 5 garden trowels ; 2 water- ing pots; 5-yard sticks (preferably graduated in inches on one side and centimeters on the other) ; 2 pieces of oil-cloth, 2 ft. square; 5 pails for soil sampling (5-lb. and 10-lb. lard pails with covers are very convenient) ; 10 baking powder can lids (3 or 4 inches across by 1 inch deep) ; 10 pie pans (granite ware preferable, or large saucers, or soup plates, will do) ; 5 pans, quart; 1 dozen each half -gallon, quart and pint screw top fruit jars; 2 pans, about 10 by 12 inches (granite ware preferred) ; 20 or 30 tomato cans; 2 long neck glass flasks, capac- ity 500 or 600 c.c, with neck about five inches long and about % inch inside diameter (Benningsen's silt flask preferred) ; 10 kerosene cans, 5 gallon; 1 box adhesive labels (Dennison's 207 very convenient) ; 2 dozen each of wide mouth bottles, capacities approximately 250 c.c, 125 c.c, and 60 c.c (8-oz., 4-oz., and 2-oz.). The following may usually be used in connection with the chemical and physical laboratories of the schools : One balance, sensitive to 1 cgm. ; 1 set of weights, 100 gms. to 1 cgm. ; 12 erlenmeyer flasks, 250 c.c. ; 12 tall beakers, 500 c.c. ; 12 porce- lain crucibles, no. ; 5 graduated cylinders, 100 c.c ; 2 packages filters, 5-in. ; 12 evaporating dishes, diam. 2y 2 in. ; 12 glass funnels, 3 in. 35 diam., short stems ; 4 doz. test tubes, 5 in. by % in. ; 2 doz. test tubes, 7 in. by 1 in. ; 6 hard glass test tubes, 6 in. by % in. ; 6 rubber stoppers, one hole, to fit hard glass tubes; 1 thermometer, to 200° C. ; 4 ther- mometers, to 212° F. ; 1 porcelain mortar, 3 in. (a heavy coffee cup will do.) CHEMICALS. For the exercises where chemical tests are made the following chemicals will be needed : One pound each of concentrated hydrochloric and nitric acids and ammonia ; 100 c.c. of each of the following test solutions of the strength usually used in chemical laboratories: potassium sulpho- cyanate, ammonium oxalate, silver nitrate, barium chloride, sodium phosphate, ammonium molybdate; sodium hydroxide, iodine; y» pound each of crystals of sodium carbonate, sodium sulphate, sodium chloride (common salt), soda-lime; 1 pint of ether; 1 pint of kero- sene ; fertilizers sufficient for the fertilizer experiments.