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Geological Survey of Kansas (1896)

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Chapter XIV--The Coal Measure Soils (Preliminary)

by Erasmus Haworth

[This chapter deals principally with a statement of methods proposed for future examinations of soils, and the scientific basis upon which such methods depend. Little work has yet been done in soil examination.]

General Principles Glacial Soils
Kansas Soils Soil Fertilization
Investigations Inaugurated by this Survey

General Principles

A preliminary discussion of the Coal Measure soils is added to the body of the Report with the hope that the statement of a few fundamental principles of soil production, and consequently soil composition, may be of value, and at the same time serve as a guide for further observations.

Soils are formed from rocks, by both mechanical and chemical disintegration. The former alone is not sufficient, for it fails to render the essential components of the soil soluble. The latter rarely if ever occurs without being accompanied by the former, and perhaps could not occur to a considerable extent without being associated with it. We may select a rock sample which the chemist finds to contain all the elements present in the best of soils, excepting organic matter, and may grind it to a fine powder; but it is not a soil, for it will not sustain vegetation unless further changed. The plant can only use the mineral matters of the soil after they have been rendered soluble, and this can only be accomplished by chemical disintegration. This latter process is brought about in nature principally through the agencies of moisture and the atmosphere. If a mass of rock is kept in contact with the air, but perfectly dry, it will not decay or disintegrate chemically to any considerable extent, Likewise, if it be kept moist, but have all air excluded from it, chemical change will take place very slowly, if at all. But if the rock is kept constantly moist, and at the same time is continually bathed by the atmosphere, decay will progress at the maximum rate. Now the rain-waters passing through the air dissolve portions of it and carry the dissolved part downwards until they are all consumed by uniting with rock constituents, which in turn are carried through processes of decay. It is those portions near the surface, therefore, that, decay the most rapidly, and hence soils are produced at and near the surface rather than at greater depths.

The influence of decaying vegetation, also, is very great. Decaying plant or animal matter assists chemical action, so that when such is intimately mixed with soils it greatly accelerates chemical changes. But this furnishes more available food for the growing plants, which in turn supply a larger amount of organic matter to decay the following season. Thus the two processes mutually assist each other, and if neither is checked by artificial or natural means the depth and richness of the soil wi1l continuously increase. But if the earthy matter is removed by drainage as fast as it is rendered soluble, as tends to be the case in hilly countries, or if the vegetation is removed as fast as grown, as is sometimes the case in certain lines of agriculture, depth and richness of the soil cannot be greatly increased. There is no good reason, therefore, why a soil should ever become exhausted. If the chemical decay can be made to keep pace with the carrying away of the products rendered soluble, a soil will remain as good as new so long as there is anything below to be decayed. It is a well-known fact that in many parts of the world the same piece of ground has been cultivated for more than a thousand years and is to-day as rich and productive as at any time in its history. We may impoverish a soil by taking away in any manner whatever the portions rendered soluble by chemical change more rapidly than new soluble compounds are produced, or we may enrich a soil by allowing it to retain a portion of the soluble parts while new ones are being formed. It is similar to one's bank account. Anything which retards the drawing out, or which increases the rate of deposits, will increase the cash value of the deposit.

But by the processes mentioned above no soluble product can be produced in the soil the essential constituents of which were not originally in the rocks whose decay produced the soils. If rocks differ in their chemical properties soils produced from them will likewise differ in richness. If a given rock system does not contain the essential constituents of a good soil, no amount of decay of any kind can add them to the soil The study of soils, therefore, becomes partially a study of the nature of the rocks which have produced them, and as such is strictly a geologic study. In nature we often find different rock systems placed one above another in such a way that on the high uplands the soil over a considerable area has been formed almost entirely from the topmost rock system, while along the bluffs and precipices the decayed products from two or more systems are falling to the valley below, adding a greater variety of materials, and hence increasing the possibilities for the production of a rich soil. In times of freshets and overflows the soils of valleys are often carried down stream many miles or even hundreds of miles by our large rivers and deposited along the banks and over the valley lands, thereby greatly increasing the possibility of mixing the proper constituents for a rich soil. These are the main conditions which cause the soils in "bottom" lands to be richer and better than the soils on uplands.

The depth of a soil also has much to do with its productiveness. This may be illustrated in the following manner: Place 10 pounds of good, rich soil in one box and 100 pounds of the same soil in a larger box. We will suppose that 1 per cent of the soil is soluble. Plant seed of any kind in each box. When the crop has grown sufficiently to absorb a tenth of a pound from the small box it must cease growing, unless something can be done to give it more mineral food, while the crop in the large box can continue to grow ten times as long, or can grow ten times as fast. As our crops are grown on the farm they never exhaust the soluble mineral matter in a season. If the soil is shallow, however, they carry it close to exhaustion every season; but if it is 5 or 10 times as deep it will have such vastly greater quantities of available plant-food that it will remain a rich soil much longer, and never will become exhausted if properly treated. The glacial soils of our northern states, and many other soils of similar depth, are usually spoken of as inexhaustible, and in fact they are if only properly treated. Many soils in America and other parts of the world are so new, that is, such small portions of the rocks have been decayed to form them, that they are very shallow, and consequently, like the soil in the small box, have their soluble material removed by cultivation so much more rapidly than new soluble products can be formed, that they soon become almost entirely impoverished.

Glacial Soils

In many parts of the world another agent has been instrumental in mingling the soils from different rocks and thereby increasing their possibilities for richness. I refer to the action of the glaciers during glacial times. It so happened that for long geologic ages certain portions of the American continent in the Great Lakes districts, and further north in Canada, were exposed to the weathering agents and suffered decay to unusually great depths. When the great masses of ice moved southward during the glacial period they scraped before them this loose mass and spread it out over the northern states, thereby giving them a coating of soil which was not formed by the decay of the rocks within their borders. Such soils, in general, are remarkably similar, even though they may be widely separated at present. They are similar not because they have all been transported by a mass of ice, but because they were originally formed from similar rock masses.

Kansas Soils

For convenience we may refer to soils produced from rocks in the same vicinity where they now exist as indigenous soils, and to those which have been transported from other localities, such as the glacial soils, and many soils along our river valleys, as exotic soils. The Coal Measures of Kansas furnish examples of both kinds. The northeast part of the state, including nearly all the counties north of the Kansas river and east of the Blue, is principally covered with the exotic glacial soils, while the greater portion of the remainder of the Coal Measures is covered with indigenous soils. On the uplands near the Kansas river to the north the glacial soils are thin, and in some places entirely wanting. But to the northward they increase in thickness until in the northern tier of counties they usually are so deep that the stratified rocks of the country are rarely visible. Such soils are almost identical with the soils in northern Missouri, southern Iowa, and: southeastern Nebraska. The general aspect of the country in the corners of these four states is remarkably similar, and, very naturally, the farmers have apparently accidentally followed almost precisely the same course in agriculture and stock-raising; Visit the localities mentioned and one cannot tell by the surface appearances, nor by the crops and stock on the farms, which one of the four states one is in.

South of the Kansas river we have indigenous soils; that is, soils produced by the disintegration of the rocks underlying them. They are, therefore, almost entirely dependent for their chemical composition upon the character of the rocks from which they have been derived. In the preceding chapters of this Report it has been shown that the rocks are of three classes, limestones, sandstones, and shales, with the latter greatly predominating in amount. These three kinds of rocks are associated in such a manner, one above another, that the limestones form great shelves, sometimes 200 or 300 feet apart, with the sandstones and shales lying between them. The latter two often grade into each other, but the former rarely changes into the latter. All of these formations dip, slightly to the west, or northwest, while the surface rises in that direction. The surface is therefore composed of a series of zones, or belts, approximating parallelism, trending north and south, or more exactly, a little northeast and southwest, each zone representing the soil produced from one shelf of rock, while its neighbors west and east equally represent zones of soil produced from the shelves first above and first below respectively.

A glance at the accompanying geologic map, and the various sections, will make this matter plain. In the southeast part of the state we have the heavy bed of the Cherokee shales. Their great thickness and the slight rise in the surface to the northwest combined cause them to occupy a belt of surface over 20 miles wide, and reaching from a hundred miles or more in Missouri to an equal distance into the Indian Territory. Over this territory the soil is almost exclusively produced from the Cherokee shales, and all of its characters correspond. It is light in color, and very fine in texture, so that in dry weather it breaks up into an exceedingly fine dust along the roads and in the cultivated fields. Such soils are usually spoken of as "ashy" soils, and the name is excellently chosen, at least so far as color and texture are concerned. In places where the sandstone is abundant its disintegration has greatly affected the appearance of the soil by yielding so much sand to be mixed with it. The apparent effect, however, is much greater than the real; for the sand grains are practically insoluble, and therefore the available plant-food nearly all comes from the decomposed shale material mixed with the sand.

To the west of this zone we have a limestone area, the Oswego limestone, and a soil dependent upon a mixture of products from the limestone and the shales. As was shown in chapter X, while discussing the topography, here and all over the Coal Measure area, the limestone shelves are broken through in many places and deep valleys cut into the underlying shales, leaving hills, bluffs and mounds with the limestone still covering their summits. It is wonderful the influence the limestones have upon the soils. As one travels northwestward from the Cherokee shale belt one can tell almost to the rod, certainly to the half mile, when one comes in contact with a soil partially produced from a limestone. The color is changed from the ashy gray to a black, or to an iron-rusty red, usually the black. The texture is changed from the fine, dusty, to a coarser granular. In wet weather it does not seem to be so plastic and impervious to water, while in dry weather it is not usually so hard and cloddy.

It is quite evident, therefore, that the two soils are dissimilar in essential properties, and in their study should be kept separate. We may pass along either zone many miles in the direction of their trend, without finding any apparent change, while near the borders a mile or two in a transverse direction will make the change complete. These two examples will illustrate the indigenous soils of the Coal Measure shales. In many places the limestone systems are thin and close together, so that their products of decay mingle freely with the soils produced from the shales over large areas. But wherever we have thick shale beds, as the Cherokee shales, the Pleasanton shales, the Lane shales, etc., we have the characteristic ashy gray soils.

From these considerations it will be readily seen that any examination or classification of our Kansas soils should be based upon geologic conditions and the geographic distribution of the different geologic formations which produce the different kinds of soils.

It may now be well to consider the origin and nature of the shales from which so large a proportion of our soils are derived, for such an understanding is essential to an intelligent knowledge of the soils. They have been formed under water, usually salt water, particularly the Kansas shales, as has already been shown in chapter IX, from the finer sediments--the mud--carried to the ocean from the dry-land areas. Along with the silt a considerable amount of sand was brought down, and was also deposited in broad, flat layers under the water. But as the sand was coarser and heavier than the silt it would not be carried as far oceanward as the latter. Hence there would be a partial separation of the two, each being deposited in part by itself, but in part with the other. The silt doubtless originally was a soil, or a portion of rock at least partially disintegrated into a soil. During the transportation all soluble products would be dissolved by the carrying waters, and therefore would not be deposited with the silt, or mud. So long as the shale material remained under the water it was deprived of the influence of the air, and therefore, chemical disintegration could not occur to produce more soluble matter. When in the course of time the movements of the earth again brought the shale-forming material above ocean water and left it in the position it now occupies it consisted of it mass of finely divided matter which was void of soluble compounds, and hence of available plant-food. But after it was lifted into dry land it would still have the air excluded, excepting those portions near the surface.

During all of this period whatever changes may have occurred within the mass were formative, rather than destructive. They have been along the line of a rearrangement of the chemical constituents producing stable, insoluble compounds, rather than unstable, soluble ones. Recently many of the fresh shales have been carefully examined with the microscope. They have invariably been found to consist of well-crystallized particles which chemically seem to be very stable. But on account of the softness of the shales and the fineness of the particles they weather rapidly, producing masses of earth which mechanically are well disintegrated, but which chemically are relatively fresh. That is the character of large portions of the soils produced from shales. They are plastic, like clay, in fact are principally clay. Their plasticity makes them run together into compact masses. Water will not soak through them readily, and when they dry they become hard and cloddy. Such materials are usually called "hard-pan," or "gumbo," and invariably can be found all over the world where soils are largely produced from shales, or where the mechanical disintegration has greatly outstripped the chemical. One usually has to dig only from 8 to 12 inches in such soils to find the yellow clay, or hard-pan.

Soil Fertilization

From the explanations given in the preceding pages, the reader has already anticipated that soil fertilization consists in increasing the amount of available plant-food within the soil, or the available soluble matter. This may be done in two ways: First, by the process nature originally uses in the formation of soils--that is, by the chemical disintegration of materials already present; and second, by the addition of one or more elements to the soil. If the agriculturist does either of these he is fertilizing his soil, enriching it, making it produce larger quantities and better qualities of plant tissue, of farm products. We will consider the two methods of fertilization separately, and in the order mentioned.

If the mass analysis of any soil shows that it has present, and in about the proper proportion, all the constituents desirable as plant-food, it will only be necessary to cause the chemical disintegration to keep pace with the sum total of the wastes of soluble matter in order to maintain the soil in the same degree of richness it originally had; and should the rate of chemical decay surpass the rate of total loss of soluble matter, the soil will continuously grow richer. Starting with such a soil, there is no excuse for allowing it to become worn out or exhausted within a thousand years. We must increase the chemical decay and decrease the loss. Of the various possible methods of obtaining the former, proper cultivation is one of the best. Stirring the soil helps to bring the air in contact with it, and to make it most susceptible to the influences of the frosts of winter and the warm sunshine of spring and summer. The freezing in winter causes the whole surface to become open arid porous, which in turn admits the air and the spring showers, all of which is very desirable because beneficial. Decaying organic matter also is an active agent in hastening chemical decay. The vegetable fiber will readily decay under atmospheric agencies, producing a great variety of chemical compounds, usually expressed under the one term "humus." Some of the compounds act chemically upon the little soil grains, producing new and soluble compounds from a portion or all of their constituents. If the organic matter is thoroughly mixed with the soil for several inches in depth it helps to make the soil loose and open, which as just stated, is a most effective method of producing chemical decay. Decaying organic matter, therefore, benefits the soil in many ways entirely outside of the addition of the nutritious material it furnishes. In a similar manner the growth of plant roots is a great benefit. The roots render the soil with which they are immediately in contact soluble. This power of plant roots is so great that they will even decompose solid rock. The deeper into the earth the plants send their roots the better service they perform, for thereby they carry this chemical disintegration much farther than otherwise would be possible; and when they finally die and decay the spaces they occupied are converted into innumerable little air-tubes which permit the relatively free circulation of air to depths which otherwise could not have been reached. This is the principal reason why the soils in our great forests are usually so rich. In their growth the mammoth trees have extracted vast quantities of mineral matter from the soil and have returned only a tithe of the same with their leaves which have annually fallen and decayed. Yet during this long period of their preying upon the soil they have returned a tenfold equivalent by the influence their roots have had upon the depths below.

Another excellent method of assisting chemical decay is to treat the soil with some chemical which will decrease or destroy the plasticity of the clay contained in the soil and in the subsoil below; for in this way the soil is made more loose and porous, and therefore more susceptible to the atmospheric agencies already mentioned. Lime is an excellent material to be used in this way; Applied to any clay it weakens or totally destroys its plasticity; gives it that flocculent property which results in the formation of little grains, producing in the soil that granular property which is so constant a mark of a good soil. Lime is strongly recommended, then, as a most excellent material to add to any and all soils which are underlaid with a yellow clay, a hard-pan, gumbo, or what not, or to any soil which is not sufficiently porous to admit of water settling rapidly after a rain. It is recommended on account of its physical action, entirely regardless of whether the soil needs more lime for plant-food or not. As limestone is so abundant in Kansas it can be obtained almost everywhere at a nominal cost, and in many instances can be spread on the fields at the rate of from 50 to 75 bushels to the acre with no outlay of money whatever. The ordinary limestone will do excellently for furnishing such lime. It may be so impure that it will not make marketable lime, but most likely the impurities themselves will be good for the soil; certainly they can do no harm. In the famous blue-grass region of Kentucky the rich soil largely owes its character, according to Professor Shaler [Twelfth An. Rep. Director U. S. Geol. Surv., article on "Soils"], to the small amount of phosphoric acid all impure limestone of the country contains. Could such a limestone be burned and spread on our Kansas soils there call be no question but that the soil would be benefited in two ways: one by the lime, and one by its impurities. It is entirely possible that we have similar limestones in our state.

The second mode of fertilization of soils is entirely different in principle from the one just described. It assumes, to begin with, that the growth of vegetation desired cannot be accomplished without the addition of one or more elements which the soil does not possess, or which it contains in too limited quantities. Before applying any such materials the rational mode of procedure would be to have mass analyses made of the soils in question to determine what materials it is necessary to have added from outside sources. If one or more essential plant foodstuffs is present in the soil, but not available because not soluble, economy would necessitate such treatment as would render them soluble. But with the soils produced from rocks, as has been shown, and the different rock formations being spread over such large parts of the surface, as has been shown to be the case for eastern Kansas, it is quite possible, indeed probable, that a soil produced from one particular rock mass may be largely or wholly destitute of one or more elements desirable for plant-food. When this has been determined by the mass analysis of the soil, it will be an easy matter to add the particular constituent necessary.

In the ordinary course of agriculture large quantities of vegetable matter are removed from the farm every year, and a corresponding amount of soluble matter, which is now stored up within the plant, is taken from the soil. The natural drainage of the soil also takes away a considerable amount, and in hilly countries this becomes a very serious matter. Whenever such removal exceeds the rate of chemical decay the soil is correspondingly impoverished, and unless something can be done in some way to check the loss, or to accelerate the decay, it is only a question of time when the soil becomes almost entirely unproductive. There may be, therefore, two fundamental reasons why outside materials should be added to any given soil: one from its original absence, and the other from its artificial absence. In such cases the direct addition to the soil of such plant-foods is desirable. They may be obtained from the commercial fertilizers, or from the common barn-yard manures.

Throughout the above discussion no reference has been made to any plant-food which is essentially organic in its nature, yet soils of whatever character are practically worthless unless soluble nitrates are present in considerable quantity. It is now very well understood that these nitrates can be gathered into the soil through the agencies of the leguminous plants, such as the clovers, beans, peas, etc. The necessary treatment to obtain the nitrogenous materials, therefore, is to add nitrogenous-bearing organic matter to the soil, or to grow some of the crops just mentioned, so that the roots may decay within the soil. Clover is the most common plant grown for this purpose, and while it is gathering from the air a supply of nitrogen for the soil its roots are also actively engaged in the decomposition of the soil materials. Clover is, therefore, aside from its value as a crop, one of the most beneficial plants that can be raised on a poor soil. But in some localities of the state clover being raised on a poor soil.

But in some localities of the state clover does not grow advantageously. This is particularly true in soils produced from the great shale beds, especially from the Cherokee shales. If one travels across the country from northwest to the southeast, it will be noticed that clover-fields are abundant in all localities where limestone soils exist. But no sooner are the light, ashy soils of the Cherokee shales reached than the clover-fields disappear. The boundary between the localities of clover-fields and no clover-fields is almost as sharp as that between the two kinds of soils. Inquiry from scores of farmers on both sides the line elicited the fact that for some reason unknown to them the clover did well on one kind of soil and could scarcely be made to grow at all on the other. Inasmuch as practically we have the same kind of farmers on both sides of the line and the same meteorological conditions, we are forced to conclude that the cause for this great difference is principally due to the difference in the soils. In such cases something must be done in some way to make the soil produced from shales capable of sustaining heavy growths of clover before any beneficial results can be obtained by clover-growing, What treatment will be necessary is one of the problems this Survey will attempt to solve.

Artificial fertilizers are both beneficial and dangerous when placed on soils. They are beneficial because, when intelligently applied, they greatly increase the productive powers of a soil. They are dangerous on account of the great possibilities for them to exercise an influence on the soil, either chemical or physical, which will interfere with the natural reproductive power soils normally possess, and thereby soon deprive the growing crops of essential food supplies. If the fertilizer, or any solvent, or vehicle it contains, should act in this way it might be used with success for a short time, but sooner or later with opposite, results. It is reliably reported that many of the farms in the older parts of America which have been treated with phosphate and potash fertilizers for years are to-day inferior in productive capacity to others in the same locality which have not been fertilized so extensively. Any fertilizer which directly or indirectly increases the plasticity of the clay within the soil or subsoil greatly retards the normal chemical decay, and thus has an injurious effect on the soil. On the other hand, any fertilizer, artificial or natural; which decreases the plasticity of the clay will to that degree be beneficial independent of the supply of food matter.

Investigations Inaugurated by This Survey

In beginning a series of investigations on the Kansas soils this Survey has taken up two lines of work: one, the getting of samples for laboratory examinations, and the other the application of various fertilizers to different kinds of soils. In the gathering of soil samples great care is taken to select localities that will furnish good representatives of the different kinds of soils viewed from the geologic standpoint. The soils produced from shales, from limestone, from sandstone, and the mixtures of two or more kinds, are gathered separately. This kind of work cannot progress far until the stratigraphic geology is pretty well worked up, and therefore must be largely deferred for some time.

The laboratory investigations will be of two general classes, physical and chemical. Recent researches in America and Europe have emphasized the importance of a proper physical condition of soil in order that the best results may be obtained by cultivation. It is quite possible to have two soils practically identical chemically, but different physically, and with reference to productiveness. The examination of the physical properties of soils will therefore be made an important branch of the laboratory investigations. The chemical work will be done by the chemical department, and will consist of ultimate annd proximate analyses, and a determination of the amount and kinds of soluble matter. In this way it is hoped to be able to determine the presence or absence of the most important plant foodstuffs, so that an intelligent idea can be had of the materials necessary to be added to the different soils in the way of fertilizers.

The experiments on the effect of different fertilizers on different soils and for different crops are intended to supplement the laboratory investigations. The plan of operation is to supply materials to reliable farmers in different parts of the country, chosen with reference to the different kinds of soils on their farms and the different kinds of crops raised. It is quite probable that both lime and gypsum, or land plaster, will be quite beneficial to all of our soils produced from shales. Such materials will be extensively tried on a great variety of soils, and for different kinds of crops. Animal fertilizers from the large packing-houses will also be tried, as will salt and other marketable products. Associated, with some of the extensive salt beds in Europe, particularly at Stassfurt, are vast deposits of potash salts. These are highly prized the world over as fertilizers for soils poor in potash. Most likely we shall find that our soils are generally deficient in this element. It will therefore be of interest to everyone to know whether our Kansas salt beds will yield any of this material. Thus far none has been produced, but if it be found everyone will be benefited.

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Kansas Geological Survey, Geology
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