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Draining for Profit, and Draining for Health
by George E. Waring
Edition 1, (October 4, 2006)
New York Orange Judd & Company, 245 Broadway.
Entered according to Act of Congress, in the year 1867, by ORANGE JUDD & CO.
At the Clerk's Office of the District Court of the United States for this Southern District of New-York.
Lovejoy & Son, Electrotypers and Stereotypers. 15 Vandewater street N.Y.
In presenting this book to the public the writer desires to say that, having in view the great importance of thorough work in land draining, and believing it advisable to avoid every thing which might be construed into an approval of half-way measures, he has purposely taken the most radical view of the whole subject, and has endeavored to emphasize the necessity for the utmost thoroughness in all draining operations, from the first staking of the lines to the final filling-in of the ditches.
That it is sometimes necessary, because of limited means, or limited time, or for other good reasons, to drain partially or imperfectly, or with a view only to temporary results, is freely acknowledged. In these cases the occasion for less completeness in the work must determine the extent to which the directions herein laid down are to be disregarded; but it is believed that, even in such cases, the principles on which those directions are founded should be always borne in mind.
NEWPORT, R.I., 1867.
ILLUSTRATIONS
Fig. 1 - A DRY SOIL. Fig. 2 - A WET SOIL. Fig. 3 - A DRAINED SOIL. Fig. 4 - MAP OF LAND, WITH SWAMPS, ROCKS, SPRINGS AND TREES. INTENDED TO REPRESENT A FIELD OF TEN ACRES BEFORE DRAINING. Fig. 5 - MAP WITH 50-FOOT SQUARES, AND CONTOUR LINES. Fig. 6 - LEVELLING INSTRUMENT. Fig. 7 - LEVELLING ROD. Fig. 8 - MAP WITH CONTOUR LINES. Fig. 9 - WELL'S CLINOMETER. Fig. 10 - STONE PIT TO CONNECT SPRING WITH DRAIN. Fig. 11 - STONE AND TILE BASIN FOR SPRING WITH DRAIN. Fig. 12 - LINE OF SATURATION BETWEEN DRAINS. Fig. 13 - HORSE-SHOE TILE. Fig. 14 - SOLE TILE. Fig. 15 - DOUBLE-SOLE TILE. Fig. 16 - ROUND TILE AND COLLAR, AND THE SAME AS LAID. Fig. 19 - THREE PROFILES OF DRAINS, WITH DIFFERENT INCLINATIONS. Fig. 20 - MAP WITH DRAINS AND CONTOUR LINES. Fig. 21 - PROFILE OF DRAIN C. Fig. 22 - SET OF TOOLS. Fig. 23 - OUTLET, SECURED WITH MASONRY AND GRATING. Fig. 24 - SILT-BASIN, BUILT TO THE SURFACE. Fig. 25 - FINISHING SPADE. Fig. 26 - FINISHING SCOOP. Fig. 27 - BRACING THE SIDES IN SOFT LAND. Fig. 28 - MEASURING STAFF. Fig. 29 - BONING ROD. Fig. 30 - POSITION OF WORKMAN AND USE OF FINISHING SCOOP. Fig. 31 - SIGHTING BY THE BONING-RODS. Fig. 32 - PICK FOR DRESSING AND PREFORATING TILE. Fig. 33 - LATERAL DRAIN ENTERING AT TOP. Fig. 34 - SECTIONAL VIEW OF JOINT. Fig. 35 - SQUARE BRICK SILT-BASIN. Fig. 36 - SILT-BASIN OF VITRIFIED PIPE. Fig. 37 - TILE SILT-BASIN. Fig. 38 - MAUL FOR RAMMING. Fig. 39 - BOARD SCRAPER FOR FILLING DITCHES. Fig. 40 - CROSS-SECTION OF DITCH (FILLED), WITH FURROW AT EACH SIDE. Fig. 41 - FOOT PICK. Fig. 42 - PUG-MILL. Fig. 43 - PLATE OF DIES. Fig. 44 - CHEAP WOODEN MACHINE. Fig. 45 - MANDRIL FOR CARRYING TILES FROM MACHINE. Fig. 46 - CLAY-KILN. Fig. 47 - DYKE AND DITCH. Fig. 48 - OLD STYLE HOUSE DRAINAGE AND SEWERAGE. Fig. 49 - MODERN HOUSE DRAINAGE AND SEWERAGE.
CONTENTS
CHAPTER I. - LAND TO BE DRAINED AND THE REASONS WHY. CHAPTER II. - HOW DRAINS ACT, AND HOW THEY AFFECT THE SOIL CHAPTER III. - HOW TO GO TO WORK TO LAY OUT A SYSTEM OF DRAINS. CHAPTER IV. - HOW TO MAKE THE DRAINS. CHAPTER V. - HOW TO TAKE CARE OF DRAINS AND DRAINED LAND. CHAPTER VI. - WHAT DRAINING COSTS. CHAPTER VII. - "WILL IT PAY?" CHAPTER VIII. - HOW TO MAKE DRAINING TILES. CHAPTER IX. - THE RECLAIMING OF SALT MARSHES. CHAPTER X. - MALARIAL DISEASES. CHAPTER XI. - HOUSE DRAINAGE AND TOWN SEWERAGE IN THEIR RELATIONS TO THE PUBLIC HEALTH. INDEX
CHAPTER I. - LAND TO BE DRAINED AND THE REASONS WHY.
Land which requires draining hangs out a sign of its condition, more or less clear, according to its circumstances, but always unmistakable to the practiced eye. Sometimes it is the broad banner of standing water, or dark, wet streaks in plowed land, when all should be dry and of even color; sometimes only a fluttering rag of distress in curling corn, or wide-cracking clay, or feeble, spindling, shivering grain, which has survived a precarious winter, on the ice-stilts that have stretched its crown above a wet soil; sometimes the quarantine flag of rank growth and dank miasmatic fogs.
To recognize these indications is the first office of the drainer; the second, to remove the causes from which they arise.
If a rule could be adopted which would cover the varied circumstances of different soils, it would be somewhat as follows: All lands, of whatever texture or kind, in which the spaces between the particles of soil are filled with water, (whether from rain or from springs,) within less than four feet of the surface of the ground, except during and immediately after heavy rains, require draining.
Of course, the particles of the soil cannot be made dry, nor should they be; but, although they should be moist themselves, they should be surrounded with air, not with water. To illustrate this: suppose that water be poured into a barrel filled with chips of wood until it runs over at the top. The spaces between the chips will be filled with water, and the chips themselves will absorb enough to become thoroughly wet;—this represents the worst condition of a wet soil. If an opening be made at the bottom of the barrel, the water which fills the spaces between the chips will be drawn off, and its place will be taken by air, while the chips themselves will remain wet from the water which they hold by absorption. A drain at the bottom of a wet field draws away the water from the free spaces between its particles, and its place is taken by air, while the particles hold, by attraction, the moisture necessary to a healthy condition of the soil.
There are vast areas of land in this country which do not need draining. The whole range of sands, gravels, light loams and moulds allow water to pass freely through them, and are sufficiently drained by nature, provided, they are as open at the bottom as throughout the mass. A sieve filled with gravel will drain perfectly; a basin filled with the same gravel will not drain at all. More than this, a sieve filled with the stiffest clay, if not "puddled,"(1) will drain completely, and so will heavy clay soils on porous and well drained subsoils. Money expended in draining such lands as do not require the operation is, of course, wasted; and when there is doubt as to the requirement, tests should be made before the outlay for so costly work is encountered.
There is, on the other hand, much land which only by thorough-draining can be rendered profitable for cultivation, or healthful for residence, and very much more, described as "ordinarily dry land," which draining would greatly improve in both productive value and salubrity.
*The Surface Indications* of the necessity for draining are various. Those of actual swamps need no description; those of land in cultivation are more or less evident at different seasons, and require more or less care in their examination, according to the circumstances under which they are manifested.
If a plowed field show, over a part or the whole of its surface, a constant appearance of dampness, indicating that, as fast as water is dried out from its upper parts, more is forced up from below, so that after a rain it is much longer than other lands in assuming the light color of dry earth, it unmistakably needs draining.
A pit, sunk to the depth of three or four feet in the earth, may collect water at its bottom, shortly after a rain;—this is a sure sign of the need of draining.
All tests of the condition of land as to water,—such as trial pits, etc.,—should be made, when practicable, during the wet spring weather, or at a time when the springs and brooks are running full. If there be much water in the soil, even at such times, it needs draining.
If the water of heavy rains stands for some time on the surface, or if water collects in the furrow while plowing, draining is necessary to bring the land to its full fertility.
Other indications may be observed in dry weather;—wide cracks in the soil are caused by the drying of clays, which, by previous soaking, have been pasted together; the curling of corn often indicates that in its early growth it has been prevented, by a wet subsoil, from sending down its roots below the reach of the sun's heat, where it would find, even in the dryest weather, sufficient moisture for a healthy growth; any severe effect of drought, except on poor sands and gravels, may be presumed to result from the same cause; and a certain wiryness of grass, together with a mossy or mouldy appearance of the ground, also indicate excessive moisture during some period of growth. The effects of drought are, of course, sometimes manifested on soils which do not require draining,—such as those poor gravels, which, from sheer poverty, do not enable plants to form vigorous and penetrating roots; but any soil of ordinary richness, which contains a fair amount of clay, will withstand even a severe drought, without great injury to its crop, if it is thoroughly drained, and is kept loose at its surface.
Poor crops are, when the cultivation of the soil is reasonably good, caused either by inherent poverty of the land, or by too great moisture during the season of early growth. Which of these causes has operated in a particular case may be easily known. Manure will correct the difficulty in the former case, but in the latter there is no real remedy short of such a system of drainage as will thoroughly relieve the soil of its surplus water.
*The Sources of the Water* in the soil are various. Either it falls directly upon the land as rain; rises into it from underlying springs; or reaches it through, or over, adjacent land.
The rain water belongs to the field on which it falls, and it would be an advantage if it could all be made to pass down through the first three or four feet of the soil, and be removed from below. Every drop of it is freighted with fertilizing matters washed out from the air, and in its descent through the ground, these are given up for the use of plants; and it performs other important work among the vegetable and mineral parts of the soil.
The spring water does not belong to the field,—not a drop of it,—and it ought not to be allowed to show itself within the reach of the roots of ordinary plants. It has fallen on other land, and, presumably, has there done its appointed work, and ought not to be allowed to convert our soil into a mere outlet passage for its removal.
The ooze water,—that which soaks out from adjoining land,—is subject to all the objections which hold against spring water, and should be rigidly excluded.
But the surface water which comes over the surface of higher ground in the vicinity, should be allowed every opportunity, which is consistent with good husbandry, to work its slow course over our soil,—not to run in such streams as will cut away the surface, nor in such quantities as to make the ground inconveniently wet, but to spread itself in beneficent irrigation, and to deposit the fertilizing matters which it contains, then to descend through a well-drained subsoil, to a free outlet.
From whatever source the water comes, it cannot remain stagnant in any soil without permanent injury to its fertility.
*The Objection to too much Water in the Soil* will be understood from the following explanation of the process of germination, (sprouting,) and growth. Other grave reasons why it is injurious will be treated in their proper order.
The first growth of the embryo plant, (in the seed,) is merely a change of form and position of the material which the seed itself contains. It requires none of the elements of the soil, and would, under the same conditions, take place as well in moist saw-dust as in the richest mold. The conditions required are, the exclusion of light; a certain degree of heat; and the presence of atmospheric air, and moisture. Any material which, without entirely excluding the air, will shade the seed from the light, yield the necessary amount of moisture, and allow the accumulation of the requisite heat, will favor the chemical changes which, under these circumstances, take place in the living seed. In proportion as the heat is reduced by the chilling effect of evaporation, and as atmospheric air is excluded, will the germination of the seed be retarded; and, in case of complete saturation for a long time, absolute decay will ensue, and the germ will die.
The accompanying illustrations, (Figures 1, 2 and 3,) from the "Minutes of Information" on Drainage, submitted by the General Board of Health to the British Parliament in 1852, represent the different conditions of the soil as to moisture, and the effect of these conditions on the germination of seeds. The figures are thus explained by Dr. Madden, from whose lecture they are taken:
"Soil, examined mechanically, is found to consist entirely of particles of all shapes and sizes, from stones and pebbles down to the finest powder; and, on account of their extreme irregularity of shape, they cannot lie so close to one another as to prevent there being passages between them, owing to which circumstance soil in the mass is always more or less porous. If, however, we proceed to examine one of the smallest particles of which soil is made up, we shall find that even this is not always solid, but is much more frequently porous, like soil in the mass. A considerable proportion of this finely-divided part of soil, the impalpable matter, as it is generally called, is found, by the aid of the microscope, to consist of broken down vegetable tissue, so that when a small portion of the finest dust from a garden or field is placed under the microscope, we have exhibited to us particles of every variety of shape and structure, of which a certain part is evidently of vegetable origin.
Fig. 1 - A DRY SOIL.
"In these figures I have given a very rude representation of these particles; and I must beg you particularly to remember that they are not meant to represent by any means accurately what the microscope exhibits, but are only designed to serve as a plan by which to illustrate the mechanical properties of the soil. On referring to Fig. 1, we perceive that there are two distinct classes of pores,—first, the large ones, which exist between the particles of soil, and second, the very minute ones, which occur in the particles themselves; and you will at the same time notice that, whereas all the larger pores,—those between the particles of soil,—communicate most freely with each other, so that they form canals, the small pores, however freely they may communicate with one another in the interior of the particle in which they occur, have no direct connection with the pores of the surrounding particles. Let us now, therefore, trace the effect of this arrangement. In Fig. 1 we perceive that these canals and pores are all empty, the soil being perfectly dry; and the canals communicating freely at the surface with the surrounding atmosphere, the whole will of course be filled with air. If in this condition a seed be placed in the soil, at a, you at once perceive that it is freely supplied with air, but there is no moisture; therefore, when soil is perfectly dry, a seed cannot grow.
Fig. 2 - A WET SOIL.
"Let us turn our attention now to Fig. 2. Here we perceive that both the pores and canals are no longer represented white, but black, this color being used to indicate water; in this instance, therefore, water has taken the place of air, or, in other words, the soil is very wet. If we observe our seed a now, we find it abundantly supplied with water, but no air. Here again, therefore, germination cannot take place. It may be well to state here that this can never occur exactly in nature, because, water having the power of dissolving air to a certain extent, the seed a in Fig. 2 is, in fact, supplied with a certain amount of this necessary substance; and, owing to this, germination does take place, although by no means under such advantageous circumstances as it would were the soil in a better condition.
Fig. 3 - A DRAINED SOIL.
"We pass on now to Fig. 3. Here we find a different state of matters. The canals are open and freely supplied with air, while the pores are filled with water; and, consequently, you perceive that, while the seed a has quite enough of air from the canals, it can never be without moisture, as every particle of soil which touches it is well supplied with this necessary ingredient. This, then, is the proper condition of soil for germination, and in fact for every period of the plant's development; and this condition occurs when the soil is moist, but not wet,—that is to say, when it has the color and appearance of being well watered, but when it is still capable of being crumbled to pieces by the hands, without any of its particles adhering together in the familiar form of mud."
As plants grow under the same conditions, as to soil, that are necessary for the germination of seeds, the foregoing explanation of the relation of water to the particles of the soil is perfectly applicable to the whole period of vegetable growth. The soil, to the entire depth occupied by roots, which, with most cultivated plants is, in drained land, from two to four feet, or even more, should be maintained, as nearly as possible, in the condition represented in Fig. 3,—that is, the particles of soil should hold water by attraction, (absorption,) and the spaces between the particles should be filled with air. Soils which require drainage are not in this condition. When they are not saturated with water, they are generally dried into lumps and clods, which are almost as impenetrable by roots as so many stones. The moisture which these clods contain is not available to plants, and their surfaces are liable to be dried by the too free circulation of air among the wide fissures between them. It is also worthy of incidental remark, that the cracking of heavy soils, shrinking by drought, is attended by the tearing asunder of the smaller roots which may have penetrated them.
*The Injurious Effects of Standing Water in the Subsoil* may be best explained in connection with the description of a soil which needs under-draining. It would be tedious, and superfluous, to attempt to detail the various geological formations and conditions which make the soil unprofitably wet, and render draining necessary. Nor,—as this work is intended as a hand-book for practical use,—is it deemed advisable to introduce the geological charts and sections, which are so often employed to illustrate the various sources of under-ground water; interesting as they are to students of the theories of agriculture, and important as the study is, their consideration here would consume space, which it is desired to devote only to the reasons for, and the practice of, thorough-draining.
To one writing in advocacy of improvements, of any kind, there is always a temptation to throw a tub to the popular whale, and to suggest some make-shift, by which a certain advantage may be obtained at half-price. It is proposed in this essay to resist that temptation, and to adhere to the rule that "whatever is worth doing, is worth doing well," in the belief that this rule applies in no other department of industry with more force than in the draining of land, whether for agricultural or for sanitary improvement. Therefore, it will not be recommended that draining be ever confined to the wettest lands only; that, in the pursuance of a penny-wisdom, drains be constructed with stones, or brush, or boards; that the antiquated horse-shoe tiles be used, because they cost less money; or that it will, in any case, be economical to make only such drains as are necessary to remove the water of large springs. The doctrine herein advanced is, that, so far as draining is applied at all, it should be done in the most thorough and complete manner, and that it is better that, in commencing this improvement, a single field be really well drained, than that the whole farm be half drained.
Of course, there are some farms which suffer from too much water, which are not worth draining at present; many more which, at the present price of frontier lands, are only worth relieving of the water which stands on the surface; and not a few on which the quantity of stone to be removed suggests the propriety of making wide ditches, in which to hide them, (using the ditches, incidentally, as drains). A hand-book of draining is not needed by the owners of these farms; their operations are simple, and they require no especial instruction for their performance. This work is addressed especially to those who occupy lands of sufficient value, from their proximity to market, to make it cheaper to cultivate well, than to buy more land for the sake of getting a larger return from poor cultivation. Wherever Indian corn is worth fifty cents a bushel, on the farm, it will pay to thoroughly drain every acre of land which needs draining. If, from want of capital, this cannot be done at once, it is best to first drain a portion of the farm, doing the work thoroughly well, and to apply the return from the improvement to its extension over other portions afterward.
In pursuance of the foregoing declaration of principles, it is left to the sagacity of the individual operator, to decide when the full effect desired can be obtained, on particular lands, without applying the regular system of depth and distance, which has been found sufficient for the worst cases. The directions of this book will be confined to the treatment of land which demands thorough work.
Such land is that which, at some time during the period of vegetation, contains stagnant water, at least in its sub-soil, within the reach of the roots of ordinary crops; in which there is not a free outlet at the bottom for all the water which it receives from the heavens, from adjoining land, or from springs; and which is more or less in the condition of standing in a great, water-tight box, with openings to let water in, but with no means for its escape, except by evaporation at the surface; or, having larger inlets than outlets, and being at times "water-logged," at least in its lower parts. The subsoil, to a great extent, consists of clay or other compact material, which is not impervious, in the sense in which india-rubber is impervious, (else it could not have become wet,) but which is sufficiently so to prevent the free escape of water. The surface soil is of a lighter or more open character, in consequence of the cultivation which it has received, or of the decayed vegetable matter and the roots which it contains.
In such land the subsoil is wet,—almost constantly wet,—and the falling rain, finding only the surface soil in a condition to receive it, soon fills this, and often more than fills it, and stands on the surface. After the rain, come wind and sun, to dry off the standing water,—to dry out the free water in the surface soil, and to drink up the water of the subsoil, which is slowly drawn from below. If no spring, or ooze, keep up the supply, and if no more rain fall, the subsoil may be dried to a considerable depth, cracking and gaping open, in wide fissures, as the clay loses its water of absorption, and shrinks. After the surface soil has become sufficiently dry, the land may be plowed, seeds will germinate, and plants will grow. If there be not too much rain during the season, nor too little, the crop may be a fair one,—if the land be rich, a very good one. It is not impossible, nor even very uncommon, for such soils to produce largely, but they are always precarious. To the labor and expense of cultivation, which fairly earn a secure return, there is added the anxiety of chance; success is greatly dependent on the weather, and the weather may be bad: Heavy rains, after planting, may cause the seed to rot in the ground, or to germinate imperfectly; heavy rains during early growth may give an unnatural development, or a feeble character to the plants; later in the season, the want of sufficient rain may cause the crop to be parched by drought, for its roots, disliking the clammy subsoil below, will have extended within only a few inches of the surface, and are subject, almost, to the direct action of the sun's heat; in harvest time, bad weather may delay the gathering until the crop is greatly injured, and fall and spring work must often be put off because of wet.
The above is no fancy sketch. Every farmer who cultivates a retentive soil will confess, that all of these inconveniences conspire, in the same season, to lessen his returns, with very damaging frequency; and nothing is more common than for him to qualify his calculations with the proviso, "if I have a good season." He prepares his ground, plants his seed, cultivates the crop, "does his best,"—thinks he does his best, that is,—and trusts to Providence to send him good weather. Such farming is attended with too much uncertainty,—with too much luck,—to be satisfactory; yet, so long as the soil remains in its undrained condition, the element of luck will continue to play a very important part in its cultivation, and bad luck will often play sad havoc with the year's accounts.
Land of this character is usually kept in grass, as long as it will bring paying crops, and is, not unfrequently, only available for pasture; but, both for hay and for pasture, it is still subject to the drawback of the uncertainty of the seasons, and in the best seasons it produces far less than it might if well drained.
The effect of this condition of the soil on the health of animals living on it, and on the health of persons living near it, is extremely unfavorable; the discussion of this branch of the question, however, is postponed to a later chapter.
Thus far, there have been considered only the effects of the undue moisture in the soil. The manner in which these effects are produced will be examined, in connection with the manner in which draining overcomes them,—reducing to the lowest possible proportion, that uncertainty which always attaches to human enterprises, and which is falsely supposed to belong especially to the cultivation of the soil.
Why is it that the farmer believes, why should any one believe, in these modern days, when the advancement of science has so simplified the industrial processes of the world, and thrown its light into so many corners, that the word "mystery" is hardly to be applied to any operation of nature, save to that which depends on the always mysterious Principle of Life,—when the effect of any combination of physical circumstances may be foretold, with almost unerring certainty,—why should we believe that the success of farming must, after all, depend mainly on chance? That an intelligent man should submit the success of his own patient efforts to the operation of "luck;" that he should deliberately bet his capital, his toil, and his experience on having a good season, or a bad one,—this is not the least of the remaining mysteries. Some chance there must be in all things,—more in farming than in mechanics, no doubt; but it should be made to take the smallest possible place in our calculations, by a careful avoidance of every condition which may place our crops at the mercy of that most uncertain of all things—the weather; and especially should this be the case, when the very means for lessening the element of chance in our calculations are the best means for increasing our crops, even in the most favorable weather.
CHAPTER II. - HOW DRAINS ACT, AND HOW THEY AFFECT THE SOIL
For reasons which will appear, in the course of this work, the only sort of drain to which reference is here made is that which consists of a conduit of burned clay, (tile,) placed at a considerable depth in the subsoil, and enclosed in a compacted bed of the stiffest earth which can conveniently be found. Stone-drains, brush-drains, sod-drains, mole-plow tracks, and the various other devices for forming a conduit for the conveying away of the soakage-water of the land, are not without the support of such arguments as are based on the expediency of make-shifts, and are, perhaps, in rare cases, advisable to be used; but, for the purposes of permanent improvement, they are neither so good nor so economical as tile-drains. The arguments of this book have reference to the latter, (as the most perfect of all drains thus far invented,) though they will apply, in a modified degree, to all underground conduits, so long as they remain free from obstructions. Concerning stone-drains, attention may properly be called to the fact that, (contrary to the general opinion of farmers,) they are very much more expensive than tile-drains. So great is the cost of cutting the ditches to the much greater size required for stone than for tiles, of handling the stones, of placing them properly in the ditches, and of covering them, after they are laid, with a suitable barrier to the rattling down of loose earth among them, that, as a mere question of first cost, it is far cheaper to buy tiles than to use stones, although these may lie on the surface of the field, and only require to be placed in the trenches. In addition to this, the great liability of stone-drains to become obstructed in a few years, and the certainty that tile-drains will, practically, last forever, are conclusive arguments in favor of the use of the latter. If the land is stony, it must be cleared; this is a proposition by itself, but if the sole object is to make drains, the best material should be used, and this material is not stone.
A well laid tile-drain has the following essential characteristics:—1. It has a free outlet for the discharge of all water which may run through it. 2. It has openings, at its joints, sufficient for the admission of all the water which may rise to the level of its floor. 3. Its floor is laid on a well regulated line of descent, so that its current may maintain a flow of uniform, or, at least, never decreasing rapidity, throughout its entire length.
Land which requires draining, is that which, at some time during the year, (either from an accumulation of the rains which fall upon it, from the lateral flow, or soakage, from adjoining land, from springs which open within it, or from a combination of two or all of these sources,) becomes filled with water, that does not readily find a natural outlet, but remains until removed by evaporation. Every considerable addition to its water wells up, and soaks its very surface; and that which is added after it is already brim full, must flow off over the surface, or lie in puddles upon it. Evaporation is a slow process, and it becomes more and more slow as the level of the water recedes from the surface, and is sheltered, by the overlying earth, from the action of sun and wind. Therefore, at least during the periods of spring and fall preparation of the land, during the early growth of plants, and often even in midsummer, the water-table,—the top of the water of saturation,—is within a few inches of the surface, preventing the natural descent of roots, and, by reason of the small space to receive fresh rains, causing an interruption of work for some days after each storm.
If such land is properly furnished with tile-drains, (having a clear and sufficient outfall, offering sufficient means of entrance to the water which reaches them, and carrying it, by a uniform or increasing descent, to the outlet,) its water will be removed to nearly, or quite, the level of the floor of the drains, and its water-table will be at the distance of some feet from the surface, leaving the spaces between the particles of all of the soil above it filled with air instead of water. The water below the drains stands at a level, like any other water that is dammed up. Rain water falling on the soil will descend by its own weight to this level, and the water will rise into the drains, as it would flow over a dam, until the proper level is again attained. Spring water entering from below, and water oozing from the adjoining land, will be removed in like manner, and the usual condition of the soil, above the water-table, will be that represented in Fig. 3, the condition which is best adapted to the growth of useful plants.
In the heaviest storms, some water will flow over the surface of even the dryest beach-sand; but, in a well drained soil the water of ordinary rains will be at once absorbed, will slowly descend toward the water-table, and will be removed by the drains, so rapidly, even in heavy clays, as to leave the ground fit for cultivation, and in a condition for steady growth, within a short time after the rain ceases. It has been estimated that a drained soil has room between its particles for about one quarter of its bulk of water;—that is, four inches of drained soil contains free space enough to receive a rain-fall one inch in depth, and, by the same token, four feet of drained soil can receive twelve inches of rain,—-more than is known to have ever fallen in twenty-four hours, since the deluge, and more than one quarter of the annual rain-fall in the United States.
As was stated in the previous chapter, the water which reaches the soil may be considered under two heads:
1st—That which reaches its surface, whether directly by rain, or by the surface flow of adjoining land.
2d—That which reaches it below the surface, by springs and by soakage from the lower portions of adjoining land.
The first of these is beneficial, because it contains fresh air, carbonic acid, ammonia, nitric acid, and heat, obtained from the atmosphere; and the flowage water contains, in addition, some of the finer or more soluble parts of the land over which it has passed. The second, is only so much dead water, which has already given up, to other soil, all that ours could absorb from it, and its effect is chilling and hurtful. This being the case, the only interest we can have in it, is to keep it down from the surface, and remove it as rapidly as possible.
The water of the first sort, on the other hand, should be arrested by every device within our reach. If the land is steep, the furrows in plowing should be run horizontally along the hill, to prevent the escape of the water over the surface, and to allow it to descend readily into the ground. Steep grass lands may have frequent, small, horizontal ditches for the same purpose. If the soil is at all heavy, it should not, when wet, be trampled by animals, lest it be puddled, and thus made less absorptive. If in cultivation, the surface should be kept loose and open, ready to receive all of the rain and irrigation water that reaches it.
In descending through the soil, this water, in summer, gives up heat which it received from the air and from the heated surface of the ground, and thus raises the temperature of the lower soil. The fertilizing matters which it has obtained from the air,—carbonic acid, ammonia and nitric acid,—are extracted from it, and held for the use of growing plants. Its fresh air, and the air which follows the descent of the water-table, carries oxygen to the organic and mineral parts of the soil, and hastens the rust and decay by which these are prepared for the uses of vegetation. The water itself supplies, by means of their power of absorption, the moisture which is needed by the particles of the soil; and, having performed its work, it goes down to the level of the water below, and, swelling the tide above the brink of the dam, sets the drains running, until it is all removed. In its descent through the ground, this water clears the passages through which it flows, leaving a better channel for the water of future rains, so that, in time, the heaviest clays, which will drain but imperfectly during the first one or two years, will pass water, to a depth of four or five feet, almost as readily as the lighter loams.
Now, imagine the drains to be closed up, leaving no outlet for the water, save at the surface. This amounts to a raising of the dam to that height, and additions to the water will bring the water-table even with the top of the soil. No provision being made for the removal of spring and soakage water, this causes serious inconvenience, and even the rain-fall, finding no room in the soil for its reception, can only lie upon, or flow over, the surface,—not yielding to the soil the fertilizing matters which it contains, but, on the contrary, washing away some of its finer and looser parts. The particles of the soil, instead of being furnished, by absorption, with a healthful amount of moisture, are made unduly wet; and the spaces between them, being filled with water, no air can enter, whereby the chemical processes by which the inert minerals, and the roots and manure, in the soil are prepared for the use of vegetation, are greatly retarded.
Instead of carrying the heat of the air, and of the surface of the ground, to the subsoil, the rain only adds so much to the amount of water to be evaporated, and increases, by so much, the chilling effect of evaporation.
Instead of opening the spaces of the soil for the more free passage of water and air, as is done by descending water, that which ascends by evaporation at the surface brings up soluble matters, which it leaves at the point where it becomes a vapor, forming a crust that prevents the free entrance of air at those times when the soil is dry enough to afford it space for circulation.
Instead of crumbling to the fine condition of a loam, as it does, when well drained, by the descent of water through it, heavy clay soil, being rapidly dried by evaporation, shrinks into hard masses, separated by wide cracks.
In short, in wet seasons, on such land, the crops will be greatly lessened, or entirely destroyed, and in dry seasons, cultivation will always be much more laborious, more hurried, and less complete, than if it were well drained.
The foregoing general statements, concerning the action of water in drained, and in undrained land, and of the effects of its removal, by gravitation, and by evaporation, are based on facts which have been developed by long practice, and on a rational application of well know principles of science. These facts and principles are worthy of examination, and they are set forth below, somewhat at length, especially with reference to Absorption and Filtration; Evaporation; Temperature; Drought; Porosity or Mellowness; and Chemical Action.
ABSORPTION AND FILTRATION.—The process of under-draining is a process of absorption and filtration, as distinguished from surface-flow and evaporation. The completeness with which the latter are prevented, and the former promoted, is the measure of the completeness of the improvement. If water lie on the surface of the ground until evaporated, or if it flow off over the surface, it will do harm; if it soak away through the soil, it will do good. The rapidity and ease with which it is absorbed, and, therefore, the extent to which under-draining is successful, depend on the physical condition of the soil, and on the manner in which its texture is affected by the drying action of sun and wind, and by the downward passage of water through it.
In drying, all soils, except pure sands, shrink, and occupy less space than when they are saturated with water. They shrink more or less, according to their composition, as will be seen by the following table of results obtained in the experiments of Schuebler:
1,000 Parts of Will Contract 1,000 Parts of Will Contract Parts. Parts. Strong Limey 50. Pure Clay 183. Soil Heavy Loam 60. Peat 200. Brick Maker's 85. Clay
Professor Johnson estimates that peat and heavy clay shrink one-fifth of their bulk.
If soil be dried suddenly, from a condition of extreme wetness, it will be divided into large masses, or clods, separated by wide cracks. A subsequent wetting of the clods, which is not sufficient to expand it to its former condition, will not entirely obliterate the cracks, and the next drying will be followed by new fissures within the clods themselves; and a frequent repetition of this process will make the network of fissures finer and finer, until the whole mass of the soil is divided to a pulverulent condition. This is the process which follows the complete draining of such lands as contain large proportions of clay or of peat. It is retarded, in proportion to the amount of the free water in the soil which is evaporated from the surface, and in proportion to the trampling of the ground, when very wet. It is greatly facilitated by frost, and especially by deep frost.
The fissures which are formed by this process are, in time, occupied by the roots of plants, which remain and decay, when the crop has been removed, and which prevent the soil from ever again closing on itself so completely as before their penetration; and each season's crop adds new roots to make the separation more complete and more universal; but it is only after the water of saturation, which occupies the lower soil for so large a part of the year, has been removed by draining, that roots can penetrate to any considerable depth, and, in fact, the cracking of undrained soils, in drying, never extends beyond the separation into large masses, because each heavy rain, by saturating the soil and expanding it to its full capacity, entirely obliterates the cracks and forms a solid mass, in which the operation has to be commenced anew with the next drying.
Mr. Gisborne, in his capital essay on "Agricultural Drainage," which appeared in the Quarterly Review, No. CLXXI, says: "We really thought that no one was so ignorant as not to be aware that clay lands always shrink and crack with drought, and the stiffer the clay the greater the shrinking, as brickmakers well know. In the great drought, 36 years ago, we saw in a very retentive soil in the Vale of Belvoir, cracks which it was not very pleasant to ride among. This very summer, on land which, with reference to this very subject, the owner stated to be impervious, we put a walking stick three feet into a sun-crack, without finding a bottom, and the whole surface was what Mr. Parkes, not inappropriately, calls a network of cracks. When heavy rain comes upon a soil in this state, of course the cracks fill, the clay imbibes the water, expands, and the cracks are abolished. But if there are four or five feet parallel drains in the land, the water passes at once into them and is carried off. In fact, when heavy rain falls upon clay lands in this cracked state, it passes off too quickly, without adequate filtration. Into the fissures of the undrained soil the roots only penetrate to be perished by the cold and wet of the succeeding winter; but in the drained soil the roots follow the threads of vegetable mold which have been washed into the cracks, and get an abiding tenure. Earth worms follow either the roots or the mold. Permanent schisms are established in the clay, and its whole character is changed. An old farmer in a midland county began with 20-inch drains across the hill, and, without ever reading a word, or, we believe, conversing with any one on the subject, poked his way, step by step, to four or five feet drains, in the line of steepest descent. Showing us his drains this spring, he said: 'They do better year by year; the water gets a habit of coming to them '—a very correct statement of fact, though not a very philosophical explanation."
Alderman Mechi, of Tiptree Hall, says: "Filtration may be too sudden, as is well enough shown by our hot sands and gravels; but I apprehend no one will ever fear rendering strong clays too porous and manageable. The object of draining is to impart to such soils the mellowness and dark color of self drained, rich and friable soil. That perfect drainage and cultivation will do this, is a well known fact. I know it in the case of my own garden. How it does so I am not chemist enough to explain in detail; but it is evident the effect is produced by the fibers of the growing crop intersecting every particle of the soil, which they never could do before draining; these, with their excretions, decompose on removal of the crop, and are acted on by the alternating air and water, which also decompose and change, in a degree, the inorganic substances of the soil. Thereby drained land, which was, before, impervious to air and water, and consequently unavailable to air and roots, to worms, or to vegetable or animal life, becomes, by drainage, populated by both, and is a great chemical laboratory, as our own atmosphere is subject to all the changes produced by animated nature."
Experience proves that the descent of water through the soil renders it more porous, so that it is easier for the water falling afterward to pass down to the drains, but no very satisfactory reason for this has been presented, beyond that which is connected with the cracking of the soil. The fact is well stated in the following extract from a letter to the Country Gentleman:
"A simple experiment will convince any farmer that the best means of permanently deepening and mellowing the soil is by thorough drainage, to afford a ready exit for all surplus moisture. Let him take in spring, while wet, a quantity of his hardest soil,—such as it is almost impossible to plow in summer,—such as presents a baked and brick-like character under the influence of drought,—and place it in a box or barrel, open at the bottom, and frequently during the season let him saturate it with water. He will find it gradually becoming more and more porous and friable,—holding water less and less perfectly as the experiment proceeds, and in the end it will attain a state best suited to the growth of plants from its deep and mellow character."
It is equally a fact that the ascent of water in the soil, together with its evaporation at the surface, has the effect of making the soil impervious to rains, and of covering the land with a crust of hard, dry earth, which forms a barrier to the free entrance of air. So far as the formation of crust is concerned, it is doubtless due to the fact that the water in the soil holds in solution certain mineral matters, which it deposits at the point of evaporation, the collection of these finely divided matters serving to completely fill the spaces between the particles of soil at the surface,—pasting them together, as it were. How far below the surface this direct action extends, cannot be definitely determined; but the process being carried on for successive years, accumulating a quantity of these fine particles, each season, they are, by cultivation, and by the action of heavy showers falling at a time when the soil is more or less dry, distributed through a certain depth, and ordinarily, in all probability, are most largely deposited at the top of the subsoil. It is found in practice that the first foot in depth of retentive soils is more retentive than that which lies below. If this opinion as to the cause of this greater imperviousness is correct, it will be readily seen how water, descending to the drains, by carrying these soluble and finer parts downward and distributing them more equally through the whole, should render the soil more porous.
Another cause of the retention of water by the surface soil, often a very serious one, is the puddling which clayey lands undergo by working them, or feeding cattle upon them, when they are wet. This is always injurious. By draining, land is made fit for working much earlier in the spring, and is sooner ready for pasturing after a rain, but, no matter how thoroughly the draining has been done, if there is much clay in the soil, the effect of the improvement will be destroyed by plowing or trampling, while very wet; this impervious condition will be removed in time, of course, but while it lasts, it places us as completely at the mercy of the weather as we were before a ditch was dug.
In connection with the use of the word impervious, it should be understood that it is not used in its strict sense, for no substance which can be wetted by water is really impervious and the most retentive soil will become wet. Gisborne states the case clearly when he says: "Is your subsoil moister after the rains of mid-winter, than it is after the drought of mid-summer? If it is, it will drain."
The proportion of the rain-fall which will filtrate through the soil to the level of the drains, varies with the composition of the soil, and with the effect that the draining has had upon them.
In a very loose, gravelly, or sandy soil, which has a perfect outlet for water below, all but the heaviest falls of rain will sink at once, while on a heavy clay, no matter how well it is drained, the process of filtration will be much more slow, and if the land be steeply inclined, some of the water of ordinarily heavy rains must flow off over the surface, unless, by horizontal plowing, or catch drains on the surface, its flow be retarded until it has time to enter the soil.
The power of drained soils to hold water, by absorption, is very great. A cubic foot of very dry soil, of favorable character, has been estimated to absorb within its particles,—holding no free water, or water of drainage,—about one-half its bulk of water; if this is true, the amount required to moisten a dry soil, four feet deep, giving no excess to be drained away, would amount to a rain fall of from 20 to 30 inches in depth. If we consider, in addition to this, the amount of water drained away, we shall see that the soil has sufficient capacity for the reception of all the rain water that falls upon it.
In connection with the question of absorption and filtration, it is interesting to investigate the movements of water in the ground. The natural tendency of water, in the soil as well as out of it, is to descend perpendicularly toward the center of the earth. If it meet a flat layer of gravel lying upon clay, and having a free outlet, it will follow the course of the gravel,—laterally,—and find the outlet; if it meet water which is dammed up in the soil, and which has an outlet at a certain elevation, as at the floor of a drain, it will raise the general level of the water, and force it out through the drain; if it meet water which has no outlet, it will raise its level until the soil is filled, or until it accumulates sufficient pressure, (head,) to force its way through the adjoining lands, or until it finds an outlet at the surface.
The first two cases named represent the condition which it is desirable to obtain, by either natural or artificial drainage; the third case is the only one which makes drainage necessary. It is a fixed rule that water, descending in the soil, will find the lowest outlet to which there exists a channel through which it can flow, and that if, after heavy rains, it rise too near the surface of the ground, the proper remedy is to tap it at a lower level, and thus remove the water table to the proper distance from the surface. This subject will be more fully treated in a future chapter, in considering the question of the depth, and the intervals, at which drains should be placed.
*Evaporation.*—By evaporation is meant the process by which a liquid assumes the form of a gas or vapor, or "dries up." Water, exposed to the air, is constantly undergoing this change. It is changed from the liquid form, and becomes a vapor in the air. Water in the form of vapor occupies nearly 2000 times the space that it filled as a liquid. As the vapor at the time of its formation is of the same temperature with the water, and, from its highly expanded condition, requires a great amount of heat to maintain it as vapor, it follows that a given quantity of water contains, in the vapory form, many times as much heat as in the liquid form. This heat is taken from surrounding substances,—from the ground and from the air,—which are thereby made much cooler. For instance, if a shower moisten the ground, on a hot summer day, the drying up of the water will cool both the ground and the air. If we place a wet cloth on the head, and hasten the evaporation of the water by fanning, we cool the head; if we wrap a wet napkin around a pitcher of water, and place it in a current of air, the water in the pitcher is made cooler, by giving up its heat to the evaporating water of the napkin; when we sprinkle water on the floor of a room, its evaporation cools the air of the room.
So great is the effect of evaporation, on the temperature of the soil, that Dr. Madden found that the soil of a drained field, in which most of the water was removed from below, was 6-1/2 deg. Far. warmer than a similar soil undrained, from which the water had to be removed by evaporation. This difference of 6-1/2 deg. is equal to a difference of elevation of 1,950 feet.
It has been found, by experiments made in England, that the average evaporation of water from wet soils is equal to a depth of two inches per month, from May to August, inclusive; in America it must be very much greater than this in the summer months, but this is surely enough for the purposes of illustration, as two inches of water, over an acre of land, would weigh about two hundred tons. The amount of heat required to evaporate this is immense, and a very large part of it is taken from the soil, which, thereby, becomes cooler, and less favorable for a rapid growth. It is usual to speak of heavy, wet lands as being "cold," and it is now seen why they are so.
If none of the water which falls on a field is removed by drainage, (natural or artificial,) and if none runs off from the surface, the whole rain-fall of a year must be removed by evaporation, and the cooling of the soil will be proportionately great. The more completely we withdraw this water from the surface, and carry it off in underground drains, the more do we reduce the amount to be removed by evaporation. In land which is well drained, the amount evaporated, even in summer, will not be sufficient to so lower the temperature of the soil as to retard the growth of plants; the small amount dried out of the particles of the soil, (water of absorption,) will only keep it from being raised to too great a heat by the mid-summer sun.
An idea of the amount of heat lost to the soil, in the evaporation of water, may be formed from the fact that to evaporate, by artificial heat, the amount of water contained in a rain-fall of two inches on an acre, (200 tons,) would require over 20 tons of coal. Of course a considerable—probably by far the larger,—part of the heat taken up in the process of evaporation is furnished by the air; but the amount abstracted from the soil is great, and is in direct proportion to the amount of water removed by this process; hence, the more we remove by draining, the more heat we retain in the ground.
The season of growth is lengthened by draining, because, by avoiding the cooling effects of evaporation, germination is more rapid, and the young plant grows steadily from the start, instead of struggling against the retarding influence of a cold soil.
*Temperature.*—The temperature of the soil has great effect on the germination of seeds, the growth of plants, and the ripening of the crops.
Gisborne says: "The evaporation of 1 lb. of water lowers the temperature of 100 lbs. of soil 10 deg.,—that is to say, that, if to 100 lbs. of soil, holding all the water it can by attraction, but containing no water of drainage, is added 1 lb. of water which it has no means of discharging, except by evaporation, it will, by the time that it has so discharged it, be 60 deg. colder than it would have been, if it had the power of discharging this 1 lb. by filtration; or, more practically, that, if rain, entering in the proportion of 1 lb. to 100 lbs. into a retentive soil, which is saturated with water of attraction, is discharged by evaporation, it lowers the temperature of that soil 10 deg.. If the soil has the means of discharging that 1 lb. of water by filtration, no effect is produced beyond what is due to the relative temperatures of the rain and of the soil."
It has been established by experiment that four times as much heat is required to evaporate a certain quantity of water, as to raise the same quantity from the freezing to the boiling point.
It is, probably, in consequence of this cooling effect of evaporation, that wet lands are warmest when shaded, because, under this condition, evaporation is less active. Such lands, in cloudy weather, form an unnatural growth, such as results in the "lodging" of grain crops, from the deficient strength of the straw which this growth produces.
In hot weather, the temperature of the lower soil is, of course, much lower than that of the air, and lower than that of the water of warm rains. If the soil is saturated with water, the water will, of course, be of an even temperature with the soil in which it lies, but if this be drained off, warm air will enter from above, and give its heat to the soil, while each rain, as it falls, will also carry its heat with it. Furthermore, the surface of the ground is sometimes excessively heated by the summer sun, and the heat thus contained is carried down to the lower soil by the descending water of rains, which thus cool the surface and warm the subsoil, both beneficial.
Mr. Josiah Parkes, one of the leading draining engineers of England, has made some experiments to test the extent to which draining affects the temperature of the soil. The results of his observations are thus stated by Gisborne: "Mr. Parkes gives the temperature on a Lancashire flat moss, but they only commence 7 inches below the surface, and do not extend to mid-summer. At that period of the year the temperature, at 7 inches, never exceeded 66 deg., and was generally from 10 deg. to 15 deg. below the temperature of the air in the shade, at 4 feet above the earth. Mr. Parkes' experiments were made simultaneously, on a drained, and on an undrained portion of the moss; and the result was, that, on a mean of 35 observations, the drained soil at 7 inches in depth was 10 deg. warmer than the undrained, at the same depth. The undrained soil never exceeded 47 deg., whereas, after a thunder storm, the drained reached 66 deg. at 7 inches, and 48 deg. at 31 inches. Such were the effects, at an early period of the year, on a black bog. They suggest some idea of what they were, when, in July or August, thunder rain at 60 deg. or 70 deg. falls on a surface heated to 130 deg., and carries down with it, into the greedy fissures of the earth, its augmented temperature. These advantages, porous soils possess by nature, and retentive ones only acquire them by drainage."
Drained land, being more open to atmospheric circulation, and having lost the water which prevented the temperature of its lower portions from being so readily affected by the temperature of the air as it is when dry, will freeze to a greater depth in winter and thaw out earlier in the spring. The deep freezing has the effect to greatly pulverize the lower soil, thus better fitting it for the support of vegetation; and the earlier thawing makes it earlier ready for spring work.
*Drought.*—At first thought, it is not unnatural to suppose that draining will increase the ill effect of too dry seasons, by removing water which might keep the soil moist. Experience has proven, however, that the result is exactly the opposite of this. Lands which suffer most from drought are most benefited by draining,—more in their greater ability to withstand drought than in any other particular.
The reasons for this action of draining become obvious, when its effects on the character of the soil are examined. There is always the same amount of water in, and about, the surface of the earth. In winter there is more in the soil than in summer, while in summer, that which has been dried out of the soil exists in the atmosphere in the form of a vapor. It is held in the vapory form by heat, which may be regarded as braces to keep it distended. When vapor comes in contact with substances sufficiently colder than itself, it gives up its heat,—thus losing its braces,—contracts, becomes liquid water, and is deposited as dew.
Many instances of this operation are familiar to all.
For instance, a cold pitcher in the summer robs the vapor in the air of its heat, and causes it to be deposited on its own surface,—of course the water comes from the atmosphere, not through the wall of the pitcher; if we breathe on a knife blade, it condenses, in the same manner, the moisture of the breath, and becomes covered with a film of-water; stone-houses are damp in summer, because the inner surface of their walls, being cooler than the atmosphere, causes its moisture to be deposited in the manner described;(2) nearly every night, in summer, the cold earth receives moisture from the atmosphere in the form of dew; a single large head of cabbage, which at night is very cold, often condenses water to the amount of a gill or more.
The same operation takes place in the soil. When the air is allowed to circulate among its lower and cooler, (because more shaded,) particles, they receive moisture by the same process of condensation. Therefore, when, by the aid of under-drains, the lower soil becomes sufficiently loose and open, to allow a circulation of air, the deposit of atmospheric moisture will keep it supplied with water, at a point easily accessible to the roots of plants.
If we wish to satisfy ourselves that this is practically correct, we have only to prepare two boxes of finely pulverized soil,—one three or four inches deep,—and the other fifteen or twenty inches deep, and place them in the sun, at midday, in summer. The thinner soil will soon be completely dried, while the deeper one, though it may have been previously dried in an oven, will soon accumulate a large amount of water on those particles which, being lower and better sheltered from the sun's heat than the particles of the thin soil, are made cooler.
We have seen that even the most retentive soil,—the stiffest clay,—is made porous by the repeated passage of water from the surface to the level of the drains, and that the ability to admit air, which plowing gives it, is maintained for a much longer time than if it were usually saturated with water which has no other means of escape than by evaporation at the surface. The power of dry soils to absorb moisture from the air may be seen by an examination of the following table of results obtained by Schuebler, who exposed 1,000 grains of dried soil of the various kinds named to the action of the air:
Kind of Soil. Amount of Water Absorbed in 24 Hours. Common Soil 22 grains. Loamy Clay 26 grains. Garden Soil 45 grains. Brickmakers' Clay 30 grains.
The effect of draining in overcoming drought, by admitting atmospheric vapor will, of course, be very much increased if the land be thoroughly loosened by cultivation, and especially if the surface be kept in an open and mellow condition.
In addition to the moisture received from the air, as above described, water is, in a porous soil, drawn up from the wetter subsoil below, by the same attractive force which acts to wet the whole of a sponge of which only the lower part touches the water;—as a hard, dry, compact sponge will absorb water much less readily than one which is loose and open, so the hard clods, into which undrained clay is dried, drink up water much less freely than they will do after draining shall have made them more friable.
The source of this underground moisture is the "water table,"—the level of the soil below the influence of the drains,—and this should be so placed that, while its water will easily rise to a point occupied by the feeding roots of the crop, it should yield as little as possible for evaporation at the surface.
Another source of moisture, in summer, is the deposit of dew on the surface of the ground. The amount of this is very difficult to determine, and accurate American experiments on the subject are wanting. Of course the amount of dew is greater here than in England, where Dr. Dalton, a skillful examiner of atmospheric phenomena, estimates the annual deposit of dew to equal a depth of five inches, or about one-fifth of the rain-fall. Water thus deposited on the soil is absorbed more or less completely, in proportion to the porosity of the ground.
The extent to which plants will be affected by drought depends, other things being equal, on the depth to which they send their roots. If these lie near the surface, they will be parched by the heat of the sun. If they strike deeply into the damper subsoil, the sun will have less effect on the source from which they obtain their moisture. Nothing tends so much to deep rooting, as the thorough draining of the soil. If the free water be withdrawn to a considerable distance from the surface, plants,—even without the valuable aid of deep and subsoil plowing,—will send their roots to great depths. Writers on this subject cite many instances in which the roots of ordinary crops "not mere hairs, but strong fibres, as large as pack-thread," sink to the depth of 4, 6, and in some instances 12 or 14 feet. 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.
It is well known among those who attend the meetings of the Farmers' Club of the American Institute, in New York, that the farm of Professor Mapes, near Newark, N.J., which maintains its wonderful fertility, year after year, without reference to wet or dry weather, has been rendered almost absolutely indifferent to the severest drought, by a course of cultivation which has been rendered possible only by under-draining. The lawns of the Central Park, which are a marvel of freshness, when the lands about the Park are burned brown, owe their vigor mainly to the complete drainage of the soil. What is true of these thoroughly cultivated lands, it is practicable to attain on all soils, which, from their compact condition, are now almost denuded of vegetation in dry seasons.
*Porosity or Mellowness.*—An open and mellow condition of the soil is always favorable for the growth of plants. They require heat, fresh air and moisture, to enable them to take up the materials on which they live, and by which they grow. We have seen that the heat of retentive soils is almost directly proportionate to the completeness with which their free water is removed by underground draining, and that, by reason of the increased facility with which air and water circulate within them, their heat is more evenly distributed among all those parts of the soil which are occupied by roots. The word moisture, in this connection, is used in contradistinction to wetness, and implies a condition of freshness and dampness,—not at all of saturation. In a saturated, a soaking-wet soil, every space between the particles is filled with water to the entire exclusion of the atmosphere, and in such a soil only aquatic plants will grow. In a dry soil, on the other hand, when the earth is contracted into clods and baked, almost as in an oven,—one of the most important conditions for growth being wanting,—nothing can thrive, save those plants which ask of the earth only an anchoring place, and seek their nourishment from the air. Both air plants and water plants have their wisely assigned places in the economy of nature, and nature provides them with ample space for growth. Agriculture, however, is directed to the production of a class of plants very different from either of these,—to those which can only grow to their greatest perfection in a soil combining, not one or two only, but all three of the conditions named above. While they require heat, they cannot dispense with the moisture which too great heat removes; while they require moisture, they cannot abide the entire exclusion of air, nor the dissipation of heat which too much water causes. The interior part of the pellets of a well pulverized soil should contain all the water that they can hold by their own absorptive power, just as the finer walls of a damp sponge hold it; while the spaces between these pellets, like the pores of the sponge, should be filled with air.
In such a soil, roots can extend in any direction, and to considerable depth, without being parched with thirst, or drowned in stagnant water, and, other things being equal, plants will grow to their greatest possible size, and all their tissues will be of the best possible texture. On rich land, which is maintained in this condition of porosity and mellowness, agriculture will produce its best results, and will encounter the fewest possible chances of failure. Of course, there are not many such soils to be found, and such absolute balance between warmth and moisture in the soil cannot be maintained at all times, and under all circumstances, but the more nearly it is maintained, the more nearly perfect will be the results of cultivation.
*Chemical Action in the Soil.*—Plants receive certain of their constituents from the soil, through their roots. The raw materials from which these constituents are obtained are the minerals of the soil, the manures which are artificially applied, water, and certain substances which are taken from the air by the absorptive action of the soil, or are brought to it by rains, or by water flowing over the surface from other land.
The mineral matters, which constitute the ashes of plants, when burned, are not mere accidental impurities which happen to be carried into their roots in solution in the water which supplies the sap, although they vary in character and proportion with each change in the mineral composition of the soil. It is proven by chemical analysis, that the composition of the ashes, not only of different species of plants, but of different parts of the same plant, have distinctive characters,—some being rich in phosphates, and others in silex; some in potash, and others in lime,—and that these characters are in a measure the same, in the same plants or parts of plants, without especial reference to the soil on which they grow. The minerals which form the ashes of plants, constitute but a very small part of the soil, and they are very sparsely distributed throughout the mass; existing in the interior of its particles, as well as upon their surfaces. As roots cannot penetrate to the interior of pebbles and compact particles of earth, in search of the food which they require, but can only take that which is exposed on their surfaces, and, as the oxydizing effect of atmospheric air is useful in preparing the crude minerals for assimilation, as well as in decomposing the particles in which they are bound up,—a process which is allied to the rusting of metals,—the more freely atmospheric air is allowed, or induced, to circulate among the inner portions of the soil, the more readily are its fertilizing parts made available for the use of roots. By no other process, is air made to enter so deeply, nor to circulate so readily in the soil, as by under-draining, and the deep cultivation which under-draining facilitates.
Of the manures which are applied to the land, those of a mineral character are affected by draining, in the same manner as the minerals which are native to the soil; while organic, or animal and vegetable, manures, (especially when applied, as is usual, in an incompletely fermented condition,) absolutely require fresh supplies of atmospheric air, to continue the decomposition which alone can prepare them for their proper effect on vegetation.
If kept saturated with water, so that the air is excluded, animal manures lie nearly inert, and vegetable matters decompose but incompletely,—yielding acids which are injurious to vegetation, and which would not be formed in the presence of a sufficient supply of air. An instance is cited by H. Wauer where sheep dung was preserved, for five years, by excessive moisture, which kept it from the air. If the soil be saturated with water in the spring, and, in summer, (by the compacting of its surface, which is caused by evaporation,) be closed against the entrance of air, manures will be but slowly decomposed, and will act but imperfectly on the crop,—if, on the other hand, a complete system of drainage be adopted, manures, (and the roots which have been left in the ground by the previous crop,) will be readily decomposed, and will exercise their full influence on the soil, and on the plants growing in it.
Again, manures are more or less effective, in proportion as they are more or less thoroughly mixed with the soil. In an undrained, retentive soil, it is not often possible to attain that perfect tilth, which is best suited for a proper admixture, and which is easily given after thorough draining.
The soil must be regarded as the laboratory in which nature, during the season of growth, is carrying on those hidden, but indispensable chemical separations, combinations, and re-combinations, by which the earth is made to bear its fruits, and to sustain its myriad life. The chief demand of this laboratory is for free ventilation. The raw material for the work is at hand,—as well in the wet soil as in the dry; but the door is sealed, the damper is closed, and only a stray whiff of air can, now and then, gain entrance,—only enough to commence an analysis, or a combination, which is choked off when half complete, leaving food for sorrel, but making none for grass. We must throw open door and window, draw away the water in which all is immersed, let in the air, with its all destroying, and, therefore, all re-creating oxygen, and leave the forces of nature's beneficent chemistry free play, deep down in the ground. Then may we hope for the full benefit of the fertilizing matters which our good soil contains, and for the full effect of the manures which we add.
With our land thoroughly improved, as has been described, we may carry on the operations of farming with as much certainty of success, and with as great immunity from the ill effects of unfavorable weather, as can be expected in any business, whose results depend on such a variety of circumstances. We shall have substituted certainty for chance, as far as it is in our power to do so, and shall have made farming an art, rather than a venture.
CHAPTER III. - HOW TO GO TO WORK TO LAY OUT A SYSTEM OF DRAINS.
How to lay out the drains; where to place the outlet; where to locate the main collecting lines; how to arrange the laterals which are to take the water from the soil and deliver it at the mains; how deep to go; at what intervals; what fall to give; and what sizes of tile to use,—these are all questions of great importance to one who is about to drain land.
On the proper adjustment of these points, depend the economy and effectiveness of the work. Time and attention given to them, before commencing actual operations, will prevent waste and avoid failure. Any person of ordinary intelligence may qualify himself to lay out under-drains and to superintend their construction,—but the knowledge which is required does not come by nature. Those who have not the time for the necessary study and practice to make a plan for draining their land, will find it economical to employ an engineer for the purpose. In this era of railroad building, there is hardly a county in America which has not a practical surveyor, who may easily qualify himself, by a study of the principles and directions herein set forth, to lay out an economical plan for draining any ordinary agricultural land, to stake the lines, and to determine the grade of the drains, and the sizes of tile with which they should be furnished.
On this subject Mr. Gisborne says: "If we should give a stimulus to amateur draining, we shall do a great deal of harm. We wish we could publish a list of the moneys which have been squandered in the last 40 years in amateur draining, either ineffectually or with very imperfect efficiency. Our own name would be inscribed in the list for a very respectable sum. Every thoughtless squire supposes that, with the aid of his ignorant bailiff, he can effect a perfect drainage of his estate; but there is a worse man behind the squire and the bailiff,—the draining conjuror. * * * * * * These fellows never go direct about their work. If they attack a spring, they try to circumvent it by some circuitous route. They never can learn that nature shows you the weakest point, and that you should assist her,—that hit him straight in the eye is as good a maxim in draining as in pugilism. * * * * * * If you wish to drain, we recommend you to take advice. We have disposed of the quack, but there is a faculty, not numerous but extending, and whose extension appears to us to be indispensable to the satisfactory progress of improvements by draining,—a faculty of draining engineers. If we wanted a profession for a lad who showed any congenial talent, we would bring him up to be a draining engineer." He then proceeds to speak of his own experience in the matter, and shows that, after more than thirty years of intelligent practice, he employed Mr. Josiah Parkes to lay out and superintend his work, and thus effected a saving, (after paying all professional charges,) of fully twelve per cent. on the cost of the draining, which was, at the same time, better executed than any that he had previously done.
It is probable that, in nearly all amateur draining, the unnecessary frequency of the lateral drains; the extravagant size of the pipes used; and the number of useless angles which result from an unskillful arrangement, would amount to an expense equal to ten times the cost of the proper superintendence, to say nothing of the imperfect manner in which the work is executed. A common impression seems to prevail, that if a 2-inch pipe is good, a 3-inch pipe must be better, and that, generally, if draining is worth doing at all, it is worth overdoing; while the great importance of having perfectly fitting connections is not readily perceived. The general result is, that most of the tile-draining in this country has been too expensive for economy, and too careless for lasting efficiency.
It is proposed to give, in this chapter, as complete a description of the preliminary engineering of draining as can be concentrated within a few pages, and a hope is entertained, that it will, at least, convey an idea of the importance of giving a full measure of thought and ingenuity to the maturing of the plan, before the execution of the work is commenced. "Farming upon paper" has never been held in high repute, but draining upon paper is less a subject for objection. With a good map of the farm, showing the comparative levels of outlet, hill, dale, and plain, and the sizes and boundaries of the different in closures, a profitable winter may be passed,—with pencil and rubber,—in deciding on a plan which will do the required work with the least possible length of drain, and which will require the least possible extra deep cutting; and in so arranging the main drains as to require the smallest possible amount of the larger and more costly pipes; or, if only a part of the farm is to be drained during the coming season, in so arranging the work that it will dovetail nicely with future operations. A mistake in actual work is costly, and, (being buried under the ground,) is not easily detected, while errors in drawing upon paper are always obvious, and are remedied without cost.
For the purpose of illustrating the various processes connected with the laying out of a system of drainage, the mode of operating on a field of ten acres will be detailed, in connection with a series of diagrams showing the progress of the work.
*A Map of the Land* is first made, from a careful survey. This should be plotted to a scale of 50 or 100 feet to the inch,(3) and should exhibit the location of obstacles which may interfere with the regularity of the drains,—such as large trees, rocks, etc., and the existing swamps, water courses, springs, and open drains. (Fig. 4.)
The next step is to locate the contour lines of the land, or the lines of equal elevation,—also called the horizontal lines,—which serve to show the shape of the surface. To do this, stake off the field into squares of 50 feet, by first running a base line through the center of the greatest length of the field, marking it with stakes at intervals of 50 feet, then stake other lines, also at intervals of 50 feet, perpendicular to the base line, and then note the position of the stakes on the maps; next, by the aid of an engineer's level and staff, ascertain the height, (above an imaginary plain below the lowest part of the field,) of the surface of the ground at each stake, and note this elevation at its proper point on the map. This gives a plot like Fig. 5. The best instrument with which to take these levels, is the ordinary telescope-level used by railroad engineers, shown in Fig. 6, which has a telescope with cross hairs intersecting each other in the center of the line of sight, and a "bubble" placed exactly parallel to this line. The instrument, fixed on a tripod, and so adjusted that it will turn to any point of the compass without disturbing the position of the bubble, will, (as will its "line of sight,") revolve in a perfectly horizontal plane. It is so placed as to command a view of a considerable stretch of the field, and its height above the imaginary plane is measured, an attendant places next to one of the stakes a levelling rod, (Fig. 7,) which is divided into feet and fractions of a foot, and is furnished with a movable target, so painted that its center point may be plainly seen. The attendant raises and lowers the target, until it comes exactly in the line of sight; its height on the rod denotes the height of the instrument above the level of the ground at that stake, and, as the height of the instrument above the imaginary plane has been reached, by subtracting one elevation from the other, the operator determines the height of the ground at that stake above the imaginary plane,—which is called the "datum line."
Fig. 4 - MAP OF LAND, WITH SWAMPS, ROCKS, SPRINGS AND TREES. INTENDED TO REPRESENT A FIELD OF TEN ACRES BEFORE DRAINING.
Fig. 5 - MAP WITH 50-FOOT SQUARES, AND CONTOUR LINES.
Fig. 6 - LEVELLING INSTRUMENT.(4)
Fig. 7 - LEVELLING ROD.
The next operation is to trace, on the plan, lines following the same level, wherever the land is of the proper height for its surface to meet them. For the purpose of illustrating this operation, lines at intervals of elevation of one foot are traced on the plan in Fig. 8. And these lines show, with sufficient accuracy for practical purposes, the elevation and rate of inclination of all parts of the field,—where it is level or nearly so, where its rise is rapid, and where slight. As the land rises one foot from the position of one line to the position of the line next above it, where the distance from one line to the next is great, the land is more nearly level, and when it is short the inclination is steeper. For instance, in the southwest corner of the plan, the land is nearly level to the 2-foot line; it rises slowly to the center of the field, and to the eastern side about one-fourth of the distance from the southern boundary, while an elevation coming down between these two valleys, and others skirting the west side of the former one and the southern side of the latter, are indicated by the greater nearness of the lines. The points at which the contour lines cross the section lines are found in the following manner: On the second line from the west side of the field we find the elevations of the 4th, 5th and 6th stakes from the southern boundary to be 1.9, 3.3, and 5.1. The contour lines, representing points of elevation of 2, 3, 4, and 5 feet above the datum line, will cross the 50-foot lines at their intersections, only where these intersections are marked in even feet. When they are marked with fractions of a foot, the lines must be made to cross at points between two intersections,—nearer to one or the other, according to their elevations,—thus between 1.9 and 3.3, the 2-foot and 3-foot contour lines must cross. The total difference of elevation, between the two points is 3.3—1.9=1.4; 10/14 of the space must be given to the even foot between the lines, and the 2-foot line should be 1/14 of the space above the point 1.9;—the 3-foot line will then come 3/14 below the point 3.3. In the same manner, the line from 3.3 to 5.1 is divided into 18 parts, of which 10 go to the space between the 4. and 5. lines, 7 are between 3.3 and the 4-foot line, and 1 between the 5-foot line and 5.1.
Fig. 8 - MAP WITH CONTOUR LINES.
With these maps, made from observations taken in the field, we are prepared to lay down, on paper, our system of drainage, and to mature a plan which shall do the necessary work with the least expenditure of labor and material. The more thoroughly this plan is considered, the more economical and effective will be the work. Having already obtained the needed information, and having it all before us, we can determine exactly the location and size of each drain, and arrange, before hand, for a rapid and satisfactory execution of the work. The only thing that may interfere with the perfect application of the plan, is the presence of masses of underground rock, within the depth to which the drains are to be laid.(5) Where these are supposed to exist, soundings should be made, by driving a 3/4-inch pointed iron rod to the rock, or to a depth of five feet where the rock falls away. By this means, measuring the distance from the soundings to the ranges of the stakes, we can denote on the map the shape and depth of sunken rocks. The shaded spot on the east side of the map, (Fig. 8,) indicates a rock three feet from the surface, which will be assumed to have been explored by sounding. |
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