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All About Soil

( Originally Published 1915 )

The Study of the Soil Interesting.—To those who have given it little attention, nothing can be more uninteresting than the study of the soil. To most school teachers the soil is dirt and nothing more; but to primitive woman, who first tilled the soil, it was a realm inhabited by spirits with power of life and death over her and hers. And so, to the normal healthy woman who is not perverted by the commercial craze for conspicuous display of wealth, the soil is a loved thing and, if she lets her natural instinct lead, as spring returns she finds herself, like her sister among the primitive people, longing to dig and plant in mother earth. To the thinking farmer the soil becomes a peculiar object of affection as it responds to his care and culture. Even poet minds, which so often see deeper and farther than common minds, have found the soil not uninteresting.

What Ruskin Saw in a Handful of Soil.—" Exclusive of animal decay, we can hardly arrive at a more absolute type of impurity than the mud or slime of a damp, overtrodden path in the outskirts of a manufacturing town. I do not say mud of the road, because that is mixed with animal refuse, but take merely an ounce or two of the blackest slime of a beaten footpath on a rainy day, near a large manufacturing town.

" The slime we shall find in most cases composed of clay (or brick dust, which is burnt clay) mixed with soot, a little sand and water. All these elements are at hopeless war with each other and destroy reciprocally each other's nature and power, competing and fighting for place at every tread of the foot; sand squeezing out clay, and clay squeezing out water, and soot meddling everywhere and defiling the whole. Let us suppose that this ounce of mud is left in perfect rest, and that the elements gather together, like to like, so that their atoms may get into closest relation possible.

" Let the clay begin; ridding itself of all foreign substances, it gradually becomes a white earth, always very beautiful, and fit, with help of congealing fire, to be made into finest porcelain, and painted on, and be kept in king's palaces. But such artificial consistence is not its best. Leave it still quiet to follow its own instinct of unity and it becomes not only white, but clear ; not only clear, but hard; not only clear and hard, but so set that it can deal with light in a wonderful way, and gather out of it the loveliest blue rays only, refusing the rest. We call it then sapphire.

" Such being the consummation of the clay, we give similar permission of quiet to the sand. It also becomes first a white earth and then proceeds to grow clear and hard, and at last arranges itself in mysterious, infinitely fine parallel lines, which have the power of reflecting not merely the blue rays, but the blue, green, purple, and red rays in the greatest beauty in which they can be seen in any fired material whatsoever. We call it then an opal.

" In next order the soot is set to work ; it cannot make itself white at first, but, instead of being discouraged, tries harder and harder and comes out clear at last, and the hardest thing in the world; and for the blackness that it had, obtains in ex-change the power of reflecting all the rays of the sun at once in the vividest blaze that any solid thing can shoot. We call it then a diamond.

" Last of all the water purifies or unites itself, contented enough if it only reaches the form of a dew drop; but if we insist on its proceeding to a more perfect consistence, it crystallizes into the shape of a star. And for the ounce of slime . . . we have . . . a sapphire, an opal, and a diamond, set in the midst of a star of snow."

The Study of the Soil Interesting to the Chemist, the Biologist, and the Physicist.—Such is the poet's vision, but the scientist finds the soil no less interesting. Be he a physicist, he finds the soil a wonderful laboratory filled with elements of different kinds going through some physical action constantly. Think of the action going on within a single cobblestone made up of a number of minerals which expand and contract at different rates with the heating and cooling of the day and the night. This gradually crumbles the stone and brushes dust particles from the faces of the tiny elements, which give us the mineral plant food.

But the soil is not alone interesting for the man enamored by physics ; it has an equal interest for the chemist, because no sooner are those dust particles set free than they begin to form some new compound, and thus the soil becomes an ever-active chemical mixture, giving many different actions and reactions.

Not only for the physicist and the chemist has the soil interest, but the biologist finds the soil a wonderful field of life and death, of trouble and extinction. The soil is loaded with bacteria of many kinds, with earthworms carrying plant stems and leaves down into the soil to set up new physical, chemical, and biological activity; with ants and bugs, with gophers, moles and snakes all making openings which let in warmth, water and air which start up renewed activity. And what shall we say of the farmer who sits by his warm fire on a cold, rainy or freezing night conscious that nature is working for him to prepare plant food for the coming crops ? Surely a little piece of God's green earth and man's cleared field should belong to every conscious soul.

The Formation of the Soil Taught First in Geography.—Though the formation of the soil belongs to physiography, or physical geography, yet the elementary treatment of the subject is given in nearly all introductory geographies, and the teacher should be prepared to tell something, and to tell especially of the formation of the soil of her own locality.

The History of the Glaciated Soil.—A wonderful history is that which tells of the formation of the soil in any given locality. I do not know where it begins, but, with our present knowledge as recorded in the geologies, we cannot go back of the time when the substance of which the earth is made existed in the form of star-dust floating through space. This star-dust was drawn together by gravity and could assume but one form, the sphere, but owing to its rotation this sphere was slightly flattened at the poles. The friction caused by these particles coming together made them hot, so that all was probably a molten mass which gradually cooled and formed a crust on the outside. The sphere went on cooling until the inside became too small for the crust, just as the contents of a plum do as the moisture escapes; then the crust of the sphere had to fold and wrinkle just as the plum rind does. Gravity drew the water to the lower places, leaving the tops of the folds exposed. These enlarged until we have much of our land. Animals and plants began to build in the water near the shores and give us our limestone, coal, etc., which crop out at many places. Then great fields of ice slid down over the northern states carrying much material from the roots of the old mountain chains just north of the United States; this material was spread over the limestone rock made by the animals and plants in the ocean water. Then the glaciers melted, and the wind, and water from the melting glaciers, and the rains redistributed the material which was again covered by glaciers, one, two, three, four, five times, and this material was each time redistributed.

Man works and sweats to get his plowing done with an iron plow, turning a furrow fourteen or sixteen inches wide and four to twelve inches deep. Too often he is unconscious of his rich inheritance from the Great Farmer who plowed the land with His great ice machine a thousand miles wide; turning a furrow hundreds of feet deep. And now every winter the Great Husbandman sends His icy needles into the ground two and three feet deep, to loosen the soil for water, air, and plant roots.

It is hardly necessary to call the teacher's attention to the fact that one reason why clay soils in the south are so hard is because the clay is never loosened by the action of frost.

The Soil Robber.—I am sorry that American industrial history does not enable me to say that the American farmer has appreciated his gift, and properly cared for and conserved God's greatest bequest to man. Population is increasing rapidly. A million and a quarter of human beings come to our country each year. If we wish to implant patriotism instead of " patriotism " we :must see that these foreigners quickly learn our language and become comfortably adjusted to the soil. These foreigners are, in the main, hard-working and honest, and they will be easily led to read our agricultural papers, which will give them both a mastery of our language and an understanding of how to care for, cultivate and maintain the fertility of our soil. It is a shame to have to say it, but we are heirs of the " soil robbers." This robbery cannot go on forever. But there is no reason to become frightened if we teach our foreigners and rising generation how to conserve the soil fertility. There is room and capacity, on and in our soil, to feed the population of the globe and not tax it as much as the soil of Egypt or Belgium is taxed.

The Study of the Soil May Inculcate Love of Country.—One of the best ways to make a foreigner love a new country is to put him quickly into possession of the knowledge that makes him master over some of its resources. One of the easiest ways to fire the imagination and ambition of our young people is to make them conscious of the possibilities that lie buried in the soil. Says Professor Roberts, in Bailey's " Cyclopedia of Agriculture ": " The average of 34 soils, analyzed by various American chemists, showed that the first eight inches of soil of an acre contained potential plant food as follows : Nitrogen 3217 pounds, phosphoric acid 3936 pounds, and potash 17,597 pounds, making a total of 24,750 pounds, or more than 12 tons. These figures make it evident that it is not fertility that is wanted, but productivity. Since even a moderate dressing of manures almost invariably increases productivity, it follows that tillage is deficient or that plant food in the soil is largely unavailable, that is, woefully lazy; or that the soil is not continuously moist enough for normal growth of plants, or that it is too moist, or that the climate is not well suited to the crops grown, or that the seeds lack potency."

The Scientific Study of the Soil a New Study.—The hope and imagination of every school child should be stimulated by the fact that no man yet knows the best way to grow any plant or animal. The science of the soil is just in its infancy, although much valuable work has been done.

Things to Teach.—There are a number of interesting things to teach children regarding the soil. One is that its blackness is largely due to decaying plant and animal matter and is an indication of fertility. Another is that plant roots need air and the soil breathes somewhat like an animal. As the wind rushes from a place it sucks the air of the soil out with it and, as the calm comes, the air rushes back into the small cavities of the soil again. Recent discoveries announced by the United States Department of Agriculture, though disputed by some, bid fair to reveal an explanation of many difficult problems in soil management. These discoveries are that each plant secretes a toxic, or poisonous substance, for plants of the same kind. These discoveries offer a partial explanation for the advantages derived from a systematic rotation of crops. They help us to understand why we may fertilize ever so much and not get much larger crops. They explain why it seems best to change the strawberry bed every two or three years and the small fruits, like raspberries and blackberries, every ten years. Though we now learn that plants, like fish confined in a small body of water, poison their media, yet it must not be forgotten that there is much truth in the older explanation that any variety of plants will soon use much of the available food while another kind of plants, which use different relative proportions of food, may thrive in that same soil.

Soils Equal to Weakest Element.—It is a law in agriculture that a soil is equal in value to its scarcest element. There are five things that our soils are likely to be deficient in : Nitrogen, potash, phosphorus, lime and water. Now the law means that if one of these is lacking, plants cannot use the others or substitute another element for the one lacking. Sometimes there may be an excess of one element, as where one hauls much barn-yard manure on to an orchard, thus furnishing an excess of nitrogen which will induce the trees to grow too much wood or to give a late growth of leaves and wood that may lead to winter killing. The injury from an excess of one element can be overcome in most instances by an application of one or more of the other elements necessary for plant food. For example, an excess of nitrogen makes necessary more potash and phosphorus. Wood ashes are an economical source of potash. A bushel of hard coal ashes around the base of an orchard tree may make the soil unattractive to insects that crawl over or burrow at the base and later climb the tree to make " wormy " fruit, though it should be said that while some lime may come from the coal ashes there is little fertilizer value in either soft or hard coal ashes.

Plates for Teaching.—The plates shown in Fig. 70 make a handy device for teaching soils, fertilizers and feeds. The plates are marked with chalk or, better, ink, and the sections numbered. There are four kinds of soil, namely, sand, clay, loam, and humus or peat. These are rarely found pure and we name the mixed soil with the name of the predominating element first as sandy-clay, peaty-clay, sandy-loam, clay-loam, etc. These soils differ in size of particles, in origin, in texture and structure, and so on. There are many names for the soils of the different parts of the United States as glacier drift, Chester loam, Penn clay, etc. One should learn the name and characteristics of the soil of his district. This is necessary in order to know how to handle it.

Plants Disintegrate Rock.—Decaying plants furnish food for the young plants growing in a soil. But they also help to disintegrate rock and thus free plant food from the faces of the soil particles. Roots of clover may be placed between two pieces of polished marble and allowed to grow there. In a few weeks it will be found that the roots have etched the marble. It is claimed that there is an abundant supply of mineral plant food in the upper eighteen inches of ordinary soil, but the minerals are locked up in combinations with the rock particles. Air, water, heating and cooling, and acids generated by both growing and decaying plants help to disintegrate these soil particles and free mineral food for the plants. Of course, if there are no plants present to take up the food when freed, it is quickly leached or washed away. Hence we should learn that fallowing in humid climates is not a good farm practice. But it is claimed that, if a soil is kept constantly damp, it sours and there are developed amoeba which prey upon the nitrifying bacteria ; for this reason it is sometimes good practice to plow in late July or early August and let the plowed field lie fallow for a month or so before sowing the winter cover crop. The roots of the legumes are believed to be especially beneficial to soils where members of the grass family have preceded or are to follow. Clover and alfalfa roots seem to thrive on the excretions of corn, oats, and wheat. Clover, vetch, soy beans, alfalfa and cowpeas are believed to tear rock to pieces faster than do members of the grass family. Then, too, the legumes have on their roots the nodules of bacteria which gather nitrogen from the soil-air and store it for future crops. An acre of alfalfa is said to store twenty-five dollars worth of nitrogen each year for the first two or three years after seeding.

Why Do We Plow?—The teacher may begin this series of lessons by letting each pupil write what he thinks are the reasons for plowing (Figs. 71-73). The answers gathered and classified probably contain the principal reasons, which are : (1) To make a reservoir for water ; (2) to loosen the soil and expose as much as possible to the action of frost and rain ; (3) to crumble the soil and thus make it more easily penetrated by plant roots; (4) to cause friction of particle on particle and thus tear off plant food ; (5) to form ridges along the sides of hills and thus form terraces to prevent water from washing away the soil as it runs down the hill instead of soaking in near the top; (6) to cover weeds, manure and other organic matter.

First reason : To make a reservoir requires deep plowing.

Second reason : To loosen the soil and expose soil particles to the action of air applies especially to fall plowing, which should crumble the soil and set the furrow slice on edge.

Third reason : To make the soil more permeable may be accomplished by different types of plowing to suit varying soil conditions, but the same general principles and the same practice may be followed—the soil may be disked or plowed, then packed with roller or, better, packer, and then the surface should be mellowed with one or more of the different kinds of harrows, that is, with the disk, pulverizer, spring toothed or spike toothed.

Fourth reason : To cause a sliding friction of soil particle on soil particle requires a steel mould-board plow which will bend the furrow slice abruptly so as to produce a shearing movement of the soil laminae. That this plow with the sharply bent mould-board draws harder there is no doubt, but it does correspondingly better work.

Fifth reason : To form ridges requires the furrow set on edge.

Sixth reason : To cover trash requires a wide furrow with the outer edge well turned over and deep plowing rather than shallow.

Since it is essential to plant life that water pass freely up and down through the soil, it is often very injurious to plow under a heavy coat of straw, corn stalks, leaves or barnyard manure, which may leave a loose layer between the furrow slice and the subsoil and thus prevent the top soil from getting water from below by capillarity.

Plants may start in ground so insulated, grow for a short time, and then stop growing, wither and die. If, however, the furrow slice is wide, deep, set nearly on edge, and the soil immediately packed and disked, there will be much less danger. Heavy coats of manure and corn stalks may well be thoroughly disked into the soil before being plowed under. Heavy sod-soils are better for having their surfaces broken before plowing.

Coarse manure, corn stalks and such things are better applied to the pasture and meadows, where they retard the escape of moisture and become partly decomposed before being plowed under.

Why Do We Cultivate?-This series of lessons may be begun much as we did the lessons on plowing. The answers will be : (1) To kill weeds ; (2) to put on a soil mulch which acts like a blanket to keep in moisture ; (3) to warm the soil by letting in the warmer air; and (4) to facilitate absorption and aeration. Children should be taught that there is little use in watering plants unless a thin soil mulch or a coat of straw, hay, or leaves is placed around the plants soon after being watered. They should also be taught that injury is often done by too deep cultivation. Deep cultivation may be best when the plants are small but, as the roots are generally longer than the stems, many lateral roots will be pulled out or cut off unless deep cultivation ceases while the plants are small.

There are many interesting problems in arithmetic which may be solved in connection with the soil and its power to retain moisture. Soil moisture is held as a very thin film around the tiny particles of soil. The children will understand this when told that each little particle wraps itself with a coat of moisture, much as a drop of water sprinkled on to a dusty floor wraps itself with a blanket of dust. Now, this being true, the capacity of a soil to hold moisture is inversely proportional to the cube of the diameters of the soil particles. That is, the finer the soil, the more moisture it holds. Professor King in his recent book, " Soil Management," figures that in a coarse, sandy soil where the soil grains average 200 to measure an inch if placed side by side, one cubic foot of such a soil has one-eighth of an acre of soil grain surface, (1) to hold hygroscopic moisture, (2) to furnish a surface to hold water-soluble plant food, (3) to furnish a surface where solution may take place. If the soil were loam it would of course be better, for if the particles measure an inch when 1200 of them are side by side, then there is in each cubic foot of the loam about one acre of soil surface. But for the water-holding capacity alone, clay is still better, for it takes 6000 particles of some clays to measure an inch. Each cubic foot of such a soil has a surface area of about five acres.

When we read or speak about the size of the soil particles, we are thinking of what the scientists call the structure of the soil. And when we think of the arrangement of the soil particles, we are thinking about the texture of the soil. Soils differ very greatly in both structure and texture and, as we have just seen, the finer the structure the greater the capacity to hold both moisture and plant food.

Soils differ greatly in their colors. The color is due to one or more of three things—the amount of decaying organic matter, of iron, or of lime. Lime and decaying plant and animal matter give the soil a dark color. Iron gives the soil a red color.

The texture and structure are apt to be due more to the kind of rock from which the soil originated and the way the soil has been managed. Both texture and structure may be studied by having the pupils stratify the soil by pouring a small handful of it into a glass of clear water, by tearing it to pieces and examining the soil particles under a microscope, or by passing it through sieves of different but known mesh and then examining the particles that pass through each sieve.

When one becomes conscious of the importance of the fineness of soil grains and that the disintegration of soil particles by rain, frost and mechanical friction liberates mineral plant food, he will readily understand the importance of the frequent turning and stirring of the soil.

The soil should not be plowed when too dry, nor plowed, disked or cultivated when so wet that it puddles, for then lumps will be formed which are very injurious to tilth. No farm operation is more important in the dry sections of our country than the getting out to the higher places in the spring, just as soon as the surfaces dry sufficiently, and disking them, lapping the disk one-half. If the disk is not lapped it may leave air spaces which hasten instead of retard evaporation of moisture.

The Soil Mulch.—Breaking the soil surface to prevent evaporation is the key to successful cropping in many places. A dust mulch should be kept on at all times when the soil is not frozen or covered with a crop. Next in importance to the early spring disking is the use of disk or harrow on the freshly plowed field, and the use of weeder, drag, pulverizer or disk after each rain to prevent the formation of a crust. By thus maintaining a dust mulch throughout the growing season we conserve moisture and warm the soil by aeration, both of which are helpful to bacterial activity and to plant development.

The disking and plowing and harrowing do much to turn up insects so that the birds may get at them. It is seldom that a field that has been properly disked, plowed and cultivated is seriously injured by insects.

Thus we find that the farmer must be master of his soil at all times as to its physical condition, its chemical constituents, its biological life, and its moisture-holding capacity.

Dry Farming.—So far, what I have written about con-serving moisture harmonizes with the rules laid down for the so-called " Dry Farming." We have much to learn from Mr. Campbell's discoveries and their application. If a teacher is in the semi-arid regions she should study very carefully that method of farming which Mr. Campbell and his associates advocate. Campbell's " Soil Culture Manual" will repay for its cost and the time necessary to master it. Since it requires about five hundred pounds of water to pass through a plant and be evaporated from its leaves in order to translocate enough food to mature a pound of seed, and seldom does a crop get enough water throughout the season to insure a maximum yield, a series of lessons on conserving soil moisture is well worth while.

In addition to the water film around soil particles and the moisture held in the " lamp-wick " roots below the plowing, a good soil should have much moisture held in decaying animal and vegetable matter which we call humus. This humus, which has been worked over by earthworms and the many different kinds of soil bacteria, acts like a sponge to hold water and nitrates. Humus also helps to neutralize the acids which tend to accumulate in the older fields and to injure the plants, perhaps mostly by keeping down the bacteria which would work over rock and organic matter to form plant food. While, as stated, a heavy layer of vegetable matter plowed under may do injury, especially if the season be dry, yet a light layer of leaves, plant stems, or manure will be of great help to the soil in furnishing its bacteria and earthworms something out of which to make humus.

While there may be danger at times of spreading insects or plant diseases, yet children should be taught that it is generally very poor economy to burn the finer yard rakings. Leaves and grass from the yard make excellent protection for the roots of the small fruit and orchard trees. The following season this material furnishes just the needed raw material for humus. If there is a suspicion that the leaves may contain blights, they can often be destroyed by composting. This consists of raking into piles, covering with a light layer of dirt and then pouring wood ashes and house slops on to the pile for a few months. This makes a pile of the richest kind of manure, which may be applied to the orchard or garden. Soap contains much potash which, if not applied too heavily, is very helpful to fruit plants.

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