Subsoil

“ Without undertaking to advance or defend any peculiar geological views of the structure of the earth, or of the depositions or formations that compose its surface, it may be said, that very often the first four feet of subsoil is composed of strata, or layers of earth of varying porosity. ”

“ The removal of excessive subsoil moisture being secured, attention should next be given to the surface of the road, which should be finished with the firmest material at hand,—with the common earth of the subsoil where nothing better can be afforded,—and which should be brought to a true grade, with a very slight slope from the centre to the edge. ”

“ Where the subsoil is open and dry, more water is needed than where it is moist or impervious. Wherever there is an impervious substratum, the subsoil accumulates moisture and the demand for water diminishes from year to year. ”

“ For this reason porous soil, covered with stout turf and underlaid by a sandy or gravelly subsoil, is best. A site on clay soil, or where the ground water approaches the surface, is damp, cold, and unhealthful. ”

“ My subsoil is very hard, requiring constant use of the pick, and sharpening of the picks every day, so that the labor of loosening the earth was one-third or one-half more than the throwing out with a shovel. ”

“ We believe, that in all cases in which the soil is deep, more or less marked good effects must be produced by its use, but of course there must be cases in which, from the defective composition of the subsoil or other causes, it must fail. ”

“ In the farmer’s parlance, the subsoil is “raw” as compared with the surface soil; it is not so suitable for plant-nutrition, and therefore must not be brought to the surface to form the seed-bed, or be incorporated with the surface soil to any considerable extent at any one time, if crop-nutrition is to be normal. It is only in the course of time, by exposure to atmospheric action as well as to that of the humus, and of plant roots, that it becomes properly adapted to perform the functions of the surface soil. ”

“ We must again dwell on the principles already emphasized, that soils must be treated according to their nature. If too damp, they must be drained; if of the fortunate quality of a sandy loam resting on a clay subsoil, they can be abundantly deepened and enriched from the start, if of a heavy clay, inclined to be cold and wet in spring, and to bake and crack in summer, skill should aim to lighten it and remove its inertia; finally, as we have shown, a light, porous soil should be treated like a spendthrift. ”

“ The coarser waste beneath is sometimes spoken of as subsoil. Soil usually contains more or less dark, carbonaceous, decaying organic matter, called humus, and is then often termed the humus layer. Soil forms not only on waste produced in place from the rock beneath, but also on materials which have been transported, such as sheets of glacial drift and river deposits. Until rocks are reduced to residual clays the work of the weather is more rapid and effective on the fragments of the mantle of waste than on the rocks from which waste is being formed. ”

“ On level lands of uniform nature and depth, they are most likely to be successful; while on undulating or hill lands it is not only very difficult to secure uniformity of soil and subsoil on areas of sufficient size, but also to prevent the washing of fertilized soil, or fertilizer in solution, from one plot to the other by the influence of heavy rains or irrigation ”

“ In humid climates like ours, sandy soils may seem very open and friable on the surface but frequently hold some unpleasant subsoil surprises. Over geologic time spans, mineral grains are slowly destroyed by weak soil acids and clay is formed from the breakdown products. Then heavy winter rainfall transports these minuscule clay particles deeper into the earth, where they concentrate. ”

“ In coming in contact with the cool moisture below, it is condensed and waters the soil, on the principle that a pitcher of cold water in a warm room has large drops of water on the outside; that water is a mere condensation of moisture in the atmosphere. The cool subsoil acts in the same way upon the atmosphere at night. ”

“ For the subsoil of the whole country is very rich, as trees of immense size and height readily demonstrate. That the surface-soil is also endued with great fertility is shown by the pleasing luxuriance of the vegetation over all the plains. ”

“ Subsoils are therefore almost always less precious and more retentive of moisture, as well as of plant-food substances in solution, than their surface soils, unless these are very rich in humus; and as the finest particles are usually those richest in available plant-food, it follows that subsoils will as a rule be found to contain larger supplies of the latter than the surface soil. ”

“ Leachy Substrata.—While we may thus overcome the disadvantages of a dense subsoil or hardpan, there is another difficulty not uncommonly met with in alluvial lands, which cannot be so readily remedied. It is the occurrence, at from two to six feet depth, of coarse sand or gravel, through which capillary moisture will not ascend, but through which irrigation water will waste rapidly, leaving the overlying soil dry. Then unless very frequent irrigation can be given, the crop will suffer from drought, unless indeed the gravel itself is filled with bottom water upon which the root-ends can draw. ”

“ Certain it is that, in a healthy, well aerated soil, any of the plants ordinarily cultivated in the garden or field will send their roots far below the parched surface soil; but if the subsoil is wet, cold, and soggy, at the time when the young crop is laying out its plan of future action, it will perforce accommodate its roots to the limited space which the comparatively dry surface soil affords. ”

“ On light and shallow soils it will do more harm than good to bring the raw subsoil to the surface, but the subsoil may with advantage be stirred and loosened by the fork, and if a little loamy clay can be worked into it the land will be permanently benefited. ”

“ The soil must be a rich, warm loam facing the south, and it will be all the better for having a clay subsoil. We must have the land underdrained once in twenty feet, the drains being three feet deep, to give us a chance to work early in the spring, and also to take off the surplus water when we come to flood the land in July. ”

“ It may be a clay-soil, a sand-soil, a calcareous soil, as the surface is composed of clay, or sand, or clay strongly mixed with lime, etc.
Subsoil.—The earth lying below the ordinary depth to which the plow or spade penetrate. Sometimes it has hardened by the running of the plow over it for a series of years; then it is called pan, as hard-pan, clay-pan, etc. It is sometimes of the same nature as the top-soil, as in clay-lands; in others it is a different earth; as when a coarse gravel underlies vegetable mold, or when clay lies beneath sandy soil. ”

“ At the surface the soil water is prevented from evaporating by a blanket of loose earth, and is thus saved in the upper subsoil and lower and middle parts of the furrow slice for the roots of the crop; loose surface soil is a good non-conductor of water. During the growth of a crop, the surface of the ground should never be left long with a crust on it, but should be stirred after each rain or after artificially watering. ”

“ Natural soils consist of substances derived from the decomposition of various kinds of rocks, the bulk consisting of clay, silica and lime, in various proportions. As regards preparation, draining is of course of the utmost importance. The ground should also be trenched to the depth of 3 ft. at least, and the deeper the better so as to bring up the subsoil—whether it be clay, sand, gravel, marl, &c.—for exposure to the weather and thus convert it from a sterile mass into a living soil teeming with bacteria. ”

“ Depth of soil, and facilities for deepening it, with the nature of the subsoil, so as to know whether it retains or parts with water, are also important considerations, because tap-rooted plants require free scope for penetrating deep into the ground. ”

“ In the second case all roots that have struck downwards into a cold uncongenial subsoil must be pruned off if they cannot be turned in a lateral direction, and all the lateral ones that have become coarse and fibreless must also be shortened back by means of a clean cut with a sharp knife, while a compost of rich loamy soil with a little bone-meal, and leaf-mould or old manure, should be filled into the trenches from which the old sterile soil has been taken. ”

“ When the crop is turned under the soil, it decomposes, and the carbon, as well as the mineral ingredients obtained from the subsoil, are deposited in the surface soil, and become of use to succeeding crops. ”

“ The thinner soil will be completely dried, while the deeper one, though it may have been perfectly dry at first, will soon accumulate a large amount of water on those particles which, being lower and more sheltered from the sun's heat than the particles of the thin soil, are made cooler.
With an open condition of subsoil, then, such as may be secured by under-draining, we entirely overcome drought. [Pg 221]
How does under-draining supply to the soil an increased amount of atmospheric fertilizers? ”

“ Such water, one must suppose, is obtained from ground water which has fallen upon the earth, has filtered through it, and is slowly flowing towards the river. The purifying agent in these cases is mainly the living humus which lies upon the surface, although the subsoil cannot be without some effect. These facts must alter our attitude towards surface wells, and must teach us what to a great extent has been admitted—that the purity of surface wells must depend more upon the mode of construction and the surroundings of the well than upon its depth. ”

“ The hole was then enlarged to the twenty-inch depth but the additional soil removed was discarded as a mixture of the surface and subsurface strata. Finally the hole was extended to the forty-inch depth and the subsoil from one groove of the auger was put into a third bag. In this manner about an equal quantity of soil was bagged from each stratum; and twenty such borings taken with an auger about one inch in diameter make a sufficient quantity to furnish to the chemist. ”

“ THE ZONE OF SOLUTION. Near the surface, where the circulation of ground water is most active, it oxidizes, corrodes, and dissolves the rocks through which it passes. It leaches soils and subsoils of their lime and other soluble minerals upon which plants depend for their food. It takes away the soluble cements of rocks; it widens fissures and joints and opens winding passages along the bedding planes; it may even remove whole beds of soluble rocks, such as rock salt, limestone, or gypsum. The work of ground water in producing landslides has already been noticed. ”

“ A soil deficient in plant food, in so far as chemical analysis is concerned, will produce far better crops when the flow of moisture is favorable than a highly fertile soil in which the water may be in deficiency or excess.
Aside from the actual rain-fall the texture of the soil, in other words its porosity, is the most important factor in determining the proper supply of moisture to the rootlets of plants. Even where the rain-fall is little, a properly porous soil in contact with a moist subsoil will furnish the moisture necessary to plant growth. ”

“ These boxes involve expense, but permit inspection and division of the flow according to the needs. They may be built of brick, stone, concrete, or even wood.
Fig. 31.—Close soils should be deeply subsoiled and underdrained. Porous, well-drained, air-filled soil is absolutely necessary. A, Subsoiled ground; B, 3 or 4 inch distribution tile; C, depth variable with the climate, 11⁄4 to 31⁄2 feet; D, 4-inch underdrain; E, depth such as would prepare land for good crop production, generally 31⁄2 to 4 feet; F, stone or other coarse material; G, gravel grading upward to coarse sand; H, loose soil. ”

“ Every one, however, is familiar with the fact, that when water is applied to the bottom of a flower-pot full of soil, it will gradually find its way to the surface, however light the soil may be. So it is in sandy soils or subsoils in the open field. If water abound at the depth of a few feet, or if it so abound at certain seasons of the year, that water will rise to the surface; and as the sun’s heat dries [Pg 137] it off by evaporation, more water will follow to supply its place. ”

“ Sandy soils are made thereby too dry and leachy, and it is a questionable proceeding to turn the heavy clays upon the top. Planters are, as a result, divided in opinion as to the wisdom of subsoiling. ”

“ At the top of our priority list for the well-being of the earth stands the injunction: conserve and build topsoil.
Topsoil is lost through erosion--wind erosion, water erosion, erosion through over cropping. It is held in place by stones, grasses, and the roots of shrubs and trees. Untouched by human hands, on the prairies and in the forests, topsoil is deepened year by year as winter frosts break up soft rocks, as dead grasses, leaves, twigs break down into humus, to become part of the topsoil and provide the nourishment for a new round of vegetation. ”

“ The roots of plants require both air and warmth. A deep stratum through which water can percolate, but in which it can never stagnate, is therefore necessary. A waterlogged soil is impenetrable by air, and owing to the continuous process of evaporation and radiation, its temperature is much below that of drained soil. The surface of the water in the supersaturated soil is known as the “water-table” and is exemplified in water standing in a well. Water will rise in clay by capillarity to a height of 50 in., in sand to 22 in. ”