Earth

EARTH. In an agricultural sense, earth is clay, sa d, loam, peat, bog earth, etc., in a mixture seldom pure, comprising various soils adapted to the growth of plants. Mold, on the contrary, is humus earth, or that arising from the decomposition of barnyard manure, leaves, or other vegetable substances. Except pure sand, earth has tenacity to a greater or lesser degree, clinging together more or less when damp, according as sand predominates in its composition; mold, except when saturated with water, easily falls apart. Thus earth is divided into three Classes: The more tenacious, as strong loams and clays; sandy soils, and humus; or mold. The loams contain the most humus, the sands the least. We have here tofore spoken of dry earth, especially dry clay, as a deodorizer. (See Deodorization.) The effect of the sun's rays on the temperature of the earth below the surface, the power of the soil in holding heat, its absorbent qualities, and power of taking up and holding moisture. and its disinte grability are among the most important uses of earths in the growth of plants, for upon these char acteristics the economy of vegetable life is chiefly due. (See article Soil.) Meteorology also exerts an important influence upon the productive capa bility of the earth. In inquiring into the qualities of soils, the natural system would be to judge from the color, cohesion, consistence, their capa bility of holding moisture, the growth of vegeta tion, including the varieties, as adapted to various soils, etc. This was, in fact, the only means the ancients had of determining the value of soils. Nevertheless, this is by no means a critical test. The color of soils, in fact, is but a slight indica tion of their true value, some very dark soils being infertile, and some light-colored soils being quite fertile. In fact, it is but little more than 100 years ago since the physical properties of soils first commanded the attention of scien tific investigators. And really, the first investi gations were limited to the weight of soils, and their facility of absorbing water. Thaer, while he paid great attention to the physical properties of soils in his Analysis of Earths, did not sub mit them to a series of comparative experiments. It was not until 1816 that Schilbler, when appointed at Hoffwyl, professor of physics and chemistry applied to agriculture, that a real stride was taken. He asked himself the ques tion: Where is the science I am expected to teach? He found it did not exist. He then entered upon the study of agriculture as a physic ist, and sought the best means for determining and comparing the diverse physical properties of soils. He found that the specific weight of earth was always in relation to its power of retaining heat, and of drying quickly; that the faCility for retaining water embraces that of absorbing the moisture and the oxygen of the air with rapidity, etc The physical properties of arable soils, and the physical influences of the atmosphere, have a greater ,direct action upon vegetation than those properties and influences purely chemical, because, the first are anterior to and serve as a basis for the last. Boussingault, psoves how far this auestion was in its infancy in his day. He says: At an epoch which is not yet very far distant, it was believed that a close connection existed between the composition and the quality of arable soil. Numerous analyses soon modified this opinion by demonstrating that the mineral elements have not always the import ance which is attributed to them. Schtibler tried even to prove that the fertility of a soil depends a great deal more upon its physical pro perties, its aggro gate condition, its aptitude for imbibition. etc , than on its chemical constitution. That which characterizes cultivable soil, whose base consists of disaggregated mineral sub stances, is the presence of organic remains more or less modified, such as humus and compost. Vegetable earth, properly called, results from this association. In regard to its intimate nature, we fear not to affirm that, in spite of its ,appar ent simplicity, we have still a very imperfect knowledge of it. This absorbing faculty, as mysterious as unexpected, which 'the soil exer cises on ammonia, lime, potash, and the salts of different bases, discovered by Thompson: and Way, is a palpable proof of it. The chemical composition and the physical properties do not admit of pronouncing upon the degree of fertil ity of earth. Direct observation is necessary. It is imperative to cultivate a plant in the soil, and ascertain its vigor aucl development. The an alysia will be useful in determining the quantity and quality of assimilating elements. The memoir of Schtiblet comprises one hundred pages. An abstract of the principal parts which may interest farmers, excluding all the tables of the physical properties of different soils we give from a work on agricultural meteorology, by M. Andre ' Poey, as follows: In determining the weight of the soil, a particular distinction is to be made between the peculiar specific gravity of the sev eral portions of earth, and the absolute weight of a determinate volume, as of a cubic inch or foot of the several soils. Sand, either in its wet or dry state, is the heaviest part of arable soil, certain fine slaty marls approaching the nearest to sand in this respect. Calcareous and silicious sands differ but little in this point, calcareous sand being, however, the heaviest of the com mon constituents of arable soil. The clays are lighter the more clay and the less sand they con tain. Lime exhibits great difference in weight, according to its fineness and mode of prepara tion. In slaked lime the weight is remarkably less, even after it has been resaturatecl with car bonic acid. The explanation of this scams to be the great expansion of quicklime on its combi nation with water. Dolomite sand, or a combi nation of lime and carbonate of magnesia, is much heavier than either of its component parts in a separate state. Its specific gravity rises to 2.82 and 2.83, and even magnesian stony marls often possess this greater weight. The carbon ates of magnesia, obtained by precipitation from solutions, are the lightest of the usual ingre dients of the soil. In arable soils magnesia is usually found in combination with lime or silica, where its form is coarser, and its physical properties resemble more closely those of sand. Compound arable soils are generally lighter as they are proportionally richer in humus. This fact alone does not positively indicate the fertility of a soil, since the humus itself differs in weight, and the other pure earths exhibit diversity of weight according to their fineness; consequently, mixed earths may acquire very different average weights. On this point specific gravity furnishes more certain evidence than absolute weight. The designations of light and heavy soils, as usually employed, refer to the different consistence of the earths, and not to their specific gravity or absolute weight; clay soils, wet and dry, are heavier than sandy soils. When different earths are artificially combined, a cubic inch of the com pound gives a greater weight than the common average of the component earths, whether mixed in equal portions, according to weight and vol ume, or in other quantities. By the term, power of the soil to contain water, we understand the property of earths to receive and retain water within their interstices, without allowing any to escape. It is of the greatest importance to vege tation, for on it depends the quantity of aqueous nourishment the soil can receive and supply to the roots of plants—an essential source of veget able nutriment. The sands are most deficient in this power; its degree varies, according to fine ness in the grain, from twenty to forty per cent. ; silicious sand has the least power of all. Gypsum powder approaches the sands in this respect, and has even less power of containing water than cal careous sand. Slaty marl, despite its proportion of clay, exhibits very little of this power, and renders soil both warm and dry. This marl is fre quently applied to the improvement of vineyards in Germany. In carbonate of lime this water holding pbwer varies according to the fineness of the particles; a distinction is important, therefore, between the fine lime separated by decantation and the earthy lime as found in the form of sand in arable lands. Carbonate of magnesia exists in a coarse-grained state, combined with lime or silicious earth, in arable soils, and retains water only in a slight degree. Humus, with its large natural proportion of half-decomposed organic. remains, as wood, leaves, roots, etc., has the great est degree of this power. One hundred parts of the fine earth formed by • decaying wood in old trees are capable of absorhin . nearly two hundred parts of water; and some light turf earths can con tain from three hundred to three hundred and sixty parts, when not dried artificially. Where we meet with the power of retaining more than ninety parts of water, we may depend upon an abundant commixture of organic matter. The two qualities of firmness and consistency of soil are of great importance in regard to the fertility and the manipulation of land; the terms, universal in husbandry, of light and heavy soil, rest mainly on these properties, and they therefore, deserve. investigation in regard to both dry and moist con ditions of the earth. If we compare the consist-. ency of earths with their weight, we shall see that the customary terms of heavy and light soil are founded upon, the cohesion of soil within itself and its adhesion to agricultural implements, and they therefore indicate its working properties rather than its weight. The comparative ease with which roots penetrate the soil will probably accord with these conditions. The consistency and firmness of soils in the dry and wet state increase in the same ratio. Clay lands, either wet or dry, are the most difficult to work; sandy soils and those containing much humus, are the most easy. The firmness and consistency of soil are not in the direct degree of its power of containing water; thus, fine lime and magnesia and humus possess but little consistency, although they can contain much water. We can not, there fore, infer the existence of the one property from that of the other. Consistency generally exceeds in clayey soils, but not invariably. Fine, slaty marl, notwithstanding its great proportion of clay has but slight consistence. The finest kind of pipe-clay in its dry state is only forty-two and therefore less by half than that of the heavy, gray clay of arable soils. Light, sandy soils gain cohe sive power by moisture; therefore, a damp cli mate, with a large average quantity of rain, will be found most advantageous to sandy districts. Even the purest sand, which in its dry state loses all its consistence and falls into a shapeless pow der, regains a certain degree of cohesiveness on again being wetted. With all the earths, adhe sion to wood exceeds that to iron; and the appar ent contradiction of the fact that, in wet weather land is more easily worked with wooden than with iron implements, is explained not by the less degree of adhesion to wood, but by the weight of the iron implements causing them to sink deeper into the soil. The diminution of the con sistency of soil by the penetration of frost is another important integer. After' the thorough freezing of soil in a wet state, its degree of con sistence is greatly decreased. This is epechilly the case with clays and soils of great firmness, where the diminution amounts to nearly one-half; with loamy clay the reduction reaches from sixty nine tc, forty-five, and with ordinary, arable soil from thirty-three to twenty. Completely dry earths suffer no change from the tvtion of frost. This is because the crystallization of the water in the interstices of the soil by freezing forces the several particles of earth from their position, and thus renders the points of contact fewer. The beneficial influence of breaking up the soil before winter sets in, to allow the frost to penetrate more readily, depends upon this diminution of consis tency. If the soil is worked in too wet a state in early spring the beneficial results are lost by again' bringing the earthy particles into closer contact. The throwing out of plants in changeable winters is caused by the alternate freezing and thawing of the ground, and the accompanying displace ment of earthy particles forcing the roots of smaller plants out of the earth, but not displac ing the larger ones. The capability of soils to become speedily dry, is a question of considerable importance in vegetation whether a soil gives up its acquired moisture again to the air quickly, or retains possession of it for a long time in its force. The terms a hot or Cold, a dry or wet, soil rest chiefly on this capacity. Sand, gypsum, and slaty marl dry most quickly, and are consequent ly called hot soils. Carbonate of lime varies in this respect according to the different forms in which it occurs. Calcareous sand dries quickly, and fine carbonate of lime slowly. The latter has, besides its chemical action oa humus, the advantage of loosening the soil after it is dried. This property of the earths, to require a longer or shorter time to become dry, might seem to stand in the same relation as their power of con taining water and, with thin layers, this is nearly always the, case; but with layers some inches in depth the proportion deviates consider ably; the deeper layers, in this case, drying more slowly, according to their degree of consistency, and to their greater or less contraction on dry ing. Dry soils, with a large proportion of clay, exhibit this variatio r in an especially striking manner Upon the diminution of bulk on dry ing, it is well known that most soils contract on drying, and cracks and fissures ensue, which have an injurious effect on vegetation, as the liner roots, which frequently supply the bulk of nourishment, are either bared or torn asunder. Gypsum diminishes its volume in an inconsider able degree. Fine carbonate of lime loses but little bulk, while clay exceeds it, and humus exhibits a remarkable degree of contraction. The addition of sand, or carbonate of lime, to clay, diminishes this property of contraction. Many kinds of marl fall into small pieces on dry ing, because of the great difference which clay and lime, the elements of marl, experience in their diminution of bulk on drying, after having been moistened, these individual parts changing their volume in different degrees, and thus caus ing a more easy disintegration. Humus experi ences, on drying, the greatest diminution of bulk, contracting at least one-fifth,and expanding again under the action of moisture. This is why the upper surface of the earth, in damp, turf bottoms, containing much humus, frequently rises or sinks several inches, according as the soil is penetrated with more or less water. The elevation of these soils is more remarkable during a sharp frost, after wet weather, the freezing, by its expansion, still further increasing the volume of the particles of water within the turf. Hence, too, the reason why these turf bottoms have, in their wet state, a remarkable elasticity if heavily trodden upon. The property of the

earths to absorb moisture from the atmosphere is important. Most of the earths which are com monly found in soils have the property, in their dry state, of absorbing moisture from the atmos phere, and this influences, considerably, their different degrees of fertility. All soils, except silitious sand, thus absorb moisture. Slaty marl" similar to the sands in some conditions, surpasses them in this respect; clay 'soils, espe cially those containing humus, absorb most freely. Humus, although possessing the greatest power of absorption, exhibits degrees of differ ence according to its kinds; purely vegetable humic acid absorbs moisture more freely than that obtained from animal manure. TLe degree of absorption lessens as soils become saturated with moisture, which generally occurs in a few days. A portion of the absorbed moisture becomes vaporized by the action of sunlight, and thus is performed a natural operation which exerts a very beneficial effect upon vegetation. The earths absorb, at night, moisture which they partially give off during the day While fertile, arable soils absorb moisture freely, this is not an infallible test of their properties, and the test requires much modification in its application. The property of earths to absorb oxygen gas from the atmosphere is also important Alex ander von Humboldt, many years ago, pointed out this property of the earths, and experiment confirms it, always providing that the earths are in a moist condition. All the earths lose this property upon drying, and regain it as soon as they are moistened. Humus exhibits it in the greatest degree: the clays approach nearest to it, and the sands absorb least. Fertile earths absorb more than those poorer in humus and clay. The included air, standing over them, at last becomes so void of oxygen, that lights are extinguished, ' and animals s die in it. The methods of absorption differ; "humus combines rattly with the oxygen, chemically, the inorganic earths absorb the gas without intimate combination. When earths are frozen or covered with an icy surface, absorption of oxygen ceases; and the action increases with the warmth of temperature, varying from 59' to 65r Fahrenheit. Many phenomena prove that oxygen is an important agent in vegetable, as well as in animal economy. It is particularly necessary to the germination of seeds and the growth of plants. By turning up the soil in any manner fresh layers are brought into contact with and fertilized by the oxygen, and as a moist condition of soil favors this absorption, it should be preserved. In relation to heat, the earths have the power of retaining the warmth which they accurnulate from the atmosphere and the heat of the sun, and of giving it out to surrounding bodies. It is differ ent from specific heat, and its degree depends upon the capacity of the body for conducting heat. The sands possess this power to the greatest extent; hence the heat and dryness of sandy districts in summer. Their slight water containing power, in consequence of which littla warmth is lost by evaporation, increases this condition. Slaty marl stands next to sand in this capacity; and this, joined to its greater power of retaining water, contributes largely to its fertility. Humus has the least power of retaining heat, and turf soils abounding in humus warm but slowly, because they contain water, only a small portion of which they lose rapidly by evaporation. Magnesia, combined with sands and slaty marls, largely possesses this heat retaining power. The greater the mass of an earth the more extensive will be its power of retaining beat. We may, therefore, from the absolute weight of an earth, conclude tolerably well in regard to the extent of its power. The various earths acquire heat from the sun in different proportions, and this property may exert a sensible influence on vegetation. Land consisting of light-colored clay warms less quickly and powerfully in the sunlight than a dark, dry soil; black garden-mold, rich in humus, becomes much warmer than meager limestone or clay. soils. Very_ different external circumstances may affect the warming of the soils, and may be classed as follows: first, the different colors of the surface earths; second, the different degrees of dampness present during the exposure of the earths to the sun's influence; third, the component materials of the earths; fourth, the different angles at which the sun's rays fall upon the soil. The influence of the color of soils on the quantity of heat received by them may be tested a follows: Place thermometers in the several sbils, covering their bulbs an eighth of an inch high with earth; sprinkle the surfaces, by means of a fine lawn sieve, with lampblack for a black color, and magnesia for a white, leaving one soil of its natural color. In August, with a temperature in the shade of 77° Fahrenheit, the increase with the black color was found by Prof. Schilbler to be from 77° to 1234° Fahrenheit; the white, from 77° to 110' Fahrenheit; and the natural color from 77° to Fahrenheit. Thus, the increase of temperature with the black colored earth was with the white, 33'; and with the natural, Other colored earths exhibit corresponding differences of degree in the temperature of their masses. When exposed for hours to the sun they never attain the the same degree of heat—the bl .ck earths acquir ing the greatest heat and the lighter ones remain ing cooler: If we expose earths of the same kind in a dry and a wet state to the sun, the wet earth never attains an equal degree of heat with the dry. The depression of temperature arising from evaporation amounts to 111° to 13f° Fahr. As long as the earths remain saturated with water they show little difference in their heat acquirin,,a powers, as they give off to the air, in this condition, nearly equal quantities of vapor in the same length of time; as they gradually dry, the difference in temperature increases. Light-colored earths, with great water-containing powers, acquire heat slowly, while dark-colored sand and slates, containing less moisture, become heated more quickly and powerfully. The different ingredients which enter into the com position of soils have, in themselves, far less influence on the capacity of soils to become warmed by the sun than their color and dryness. If we impart, artificially, to earths of the same color and expose them in a similarly dry con dition to the sun, the differences in temperature will be inconsiderable: so that the various capacities of earths, in their natural state, for receiving heat from the sun, depend particularly upon their color and dryness. The inclination of the ground toward the sun has a very consider able influence on the degree of heat which the soil receives from its rays, and the greater warmth is produced as the incidence of the ray approaches more nearly to a right angle, or 90°, with the surface. If the actual increase of the tempera ture in the sun over that in the shade be between 45' and 63°, as is often the case on clear summer days, this increase would be only half as, great if the same light spread itself, in a more slanting direction, over a surface twice as extended. This is the reason why heat so frequently increases on the slopes of mountains and rocks which have an inclinatiqn toward the south. When the sun is at an elevation of 60° above the horizon, as is more or less the case toward noon in the middle of summer, the sun's rays fall on the slopes of mountains which are raised to an inclination of 30° to the horizon, at a right angle; but even in the later months of summer the sun's rays frequently fall on them under a right angle in cases where the slopes are yet steeper. Such declivities, particularly in geographical lati tude of Germany, are therefore peculiarly suited to the cultivation of plants which require a high temperature, such as the vine. By an accurate comparison of the power of the sun's ray's to warm the soil, with reference to the different seasons, we shall perceive more distinctly the influence of the different inclinations of the ground toward the sun. The capacity of soils to develop heat within themselves on being moistened is that powdery substances in general, and consequently the earths, possess the property of developing warmth when moistened while in dry state; but in nature they are scarcely ever found in this perfectly dry condition. The rain falling in warm seasons is many degreesicolder than the lower stratum of the atmosphere and the upper surface of the earth, which it immedi ately moistens; so that the earth in bot weather becomes rather cooler than otherwise by the rain. Wheu the earth has previously been very dry, the cooling of it by the rain can only be reduced about Fahr., and this would have little effect on vegetation, and in the colder seasons, when the earth is already damp, so slight a development must be inappreciable. The galvanic and elec trical relations of the earth show that the pure earths, as sand, lime, magnesia, and gypsum, in their dry state, are non-conductors, the clays are imperfect conductors, and the clayey earths are weak, imperfect conductors. The presence of the moisture and of oxide of iron, found in all the clays, appears to lie the base of this phenom enon. Upon the influence of the simple earths on the germination of seeds the development of the germ depends upon the looseness, moisture, and temperature of the soil, as well as upon its warmth and consistence. In moist silicions and calcareous sand the grains germinate in summer in a few days, and develop well, but suffer as hot weather approaches. In gypsum powder they develop indifferently. In sandy clay no proper development takes place. This is also the case in loamy and stiff clay. In pure clay no change wlsatever occurs, hut the grains develop well when transferred to proper soil. In pure carbonate of lime, carbonate of magnesia, and slaty marl, as well as in pure humus, gar den mold, and arable soil, the seed germinate well—the young plants in warm weather devel oping themselves most beautifully in the humus, and in the carbonate of magnesia, in conse quence, probably, of the greater power of contain ing water which these earths possess. Upon soil, as adapted to climate, we shall find that in such ' warm countries as have also a small mean quantity of rain, those kinds of soil which have , a great power of containing water will; if other circumstances are the same, be the best; while those soils which have, on the contrary, a small power of containing water will be found better suited for countries with a greater amount of rain. Those very soils, therefore, may be fertile for one country which become no longer so for another, under a change of external circum stances; the usual alternation of ,dry and wet years being on the Same principle, more favorable to the one or to the other country, according as their predominating soils respectively possess a greater or less degree of this power of containing water. To summarize the whole, in the exam ination of soils, the determination of their power of containing water, and of their weight, con sistency, and color, in connection with their chemical analysis will, in the majority of cases. be sufficient to enable us to conclude, with great' probability, as to their remaining physical properties. The more an earth weighs, the greater also in general is its power of retaining heat; the darker its color, and at the same time the smaller its power of retaining water, the more quickly and strongly will it be heated by the sun's rays; the greater its power of contain ing water, the more has it in general the power also of absorbing moisture from the atmosphere when it is in a dry state, and oxygen when it is in a, damp state, and the slower it usually is to become dry, especially when it is endued at the same time with a high degree of consistency. Lastly, the greater the power of containing water, and also the greater the consistency of a soil, the colder and wetter of course that soil will be, as well as the stiffer to work, either in a wet or dry state, and the more judicious there fore will it be to break it up before the setting in of the frost, in order that its consistency be improved by the due penetration of the frost during the winter; and for the cultivation of many plants, the more requisite will it be found for the permanent improvement of such a soil, to counteract its too great consistency and power of containing water by mixing it with looser earths, lime, marl, coal or wood ashes and sand. If soils of different kinds be wetted until the fluid drops, it will be found, as determined by Schtibler, that 100 pounds of dry sand retain 25 pounds of water; 100 of calcareous sand, 29 of water; 100 of loamy soil, 40 of water; 100 of ' clay loam, 50 of water; 100 of strong clay, 79 of water; 100 of peat, 100 and more. Good soils hold from forty to fifty per cent. of water. Soils not only hold water, but absorb it from the air unequally. Thus, a quantity spread out to the same extent of sand, absorbed 0 pounds of water of calcareous sand, 3 of water; sandy loam, 21 of water; strong clay,30 of water; garden mold, 35 of water. In the same way, they retain moisture very unequally, sand losing it four times more rapidly than mold. A well-tilled soil is continually absorbing from the air, gaseous matter, and its fertility is, in a considerable degree, connected with this property. Molds absorb eleven times, and clay nine times as fast as sand. Black, well tilled, and drained soils become more rapidly heated, and to a greater degree than such as are wet, of a light color, or baked. In the same way, those that heat rapidly, cool rapidly, and are • more subject, to frosts. By experiments, mold cools in one third the time, and clay in two thirds the time of sand; so that, if they be equally heated, the sand will he warm for hours after the mold is cold. Hence the latter absorbs dew and contracts frost much more quickly than sandy soils. The adhesiveness of earth is an important integer. Pusey, in measuring- the force neces sary to turn furrows in various soils, found the required draft to be, for loamy sand, 230 pounds; for sandy loam, 250 pounds; for peat soil, 280 pounds; for clay loam, 400 pounds; for strong clay, 661 pounds. Thus it appears that the toughest soil required nearly three times the force , to plow it, that the most friable soil did. Im provements in plows of late years have rednced the force necessary in plowing,fully twenty per cent. Coal ashes, the spent ashes of soap makers, sand, vegetable matter, strawy manure, pow dered charcoal, baked and pulverized clay, and lime, lighten a stiff soil, and clay marl, air-slacked lime and wood ashes, stiffen those too porous. So again, as to the physical qualities of earths, light soils are usually fertile where they rest on pretty stiff clay, a stiff clay resting, on a porous sub-soil, retains sufficient water to ensure fertility. Thus we see, the character of any soil is modified in a great measure, and as to fer tility depends very much upon the nature of the sub-soil. All these being important for farmers to understand,