THE drainage of imperfectly drained and saturated soils used in crop production is a well established practice." True. In fact, tile drainage probably is too well established in many places. We have installed so much tile that the community water supply has been adversely affected, to say nothing of the even more serious problem of crop yields. The wisdom that grows from experience tells us that drain tile installed where it is not imperatively needed is the surest route to low crop production.

Perhaps the most serious indictments that can be drawn against tile drainage are these: first, that the land where the rain falls is likely to need the water after it has been carried away through the tile; and, second, that innocent people down-stream are apt to be disturbed by floods that are needlessly high because of water wasted through unnecessary tile installations. Tile, then, is a disturbing factor in relation to both local water resources and frequently recurring floods. It consequently becomes the obligation of everybody concerned with the elimination of an aggravating wet spot to think far beyond that immediate need before deciding to throw additional water into the streams.

That much unnecessary tile is laid with full approval of farm specialists is indicated by this further quotation taken from page 723 of the United States Department of Agriculture Yearbook, 1938:-

For years some farmers have seen wet spots in good fields " drown out" with loss of labor, fertilizer, and seed, not to mention the seldom considered rental value of the land. Yet they made little or no attempt at drainage until they changed from horses to tractors. When the heavy machinery mired down they decided to drain. Realizing the seriousness of the situation in holding up the sale of farm machinery, and possibly wishing to improve the farmers' ability to buy new equipment, one manufacturer published a bulletin on drainage (Drain the Wet Land, by R. A. Hayne, Chicago, 1921), even though the company produced no drainage tools.

" Wet spots " present the visual evidence that tile is apparently needed. They appear on land which originally did not permit water to stand. And as the years pass, more and more of the land that formerly needed no sub-surface drainage develops these wet spots. Before we can properly diagnose this mania for excessive drainage, we should know what these wet spots really are and why they develop where they do. It will help our analysis to consider the apparently complete lack of under-standing of soil facts displayed some time ago at a meeting of potato growers when this matter came up for discussion. The incident is illuminating.

A drainage problem had been found on the land of one of these farmers. He had discovered that water stood in a certain low spot in one field. He knew that there was tile not far from where this water stood. Search, after the water was gone, disclosed that the tile was directly under the centre of the pool. Examination at the outlet while the water still stood on the land showed that the tile was running, and that it was not loaded, but that it could easily have removed the standing water. Yet the water stood for days just over this active tile line.

The land in question was heavy, lake-laid clay a few miles from Lake Erie. The verdict of the farmers in conference was that this heavy clay had been worked too much, or when it was too wet, and had become puddled. Clay in such condition conducts water only by very slow capillarity; so this verdict was probably correct. At any rate, it squares well with the slow rate at which the standing water disappeared. Trowelling by the mouldboard plough when soil is too wet does for it just what a sow does to the bottom of her wallow when she finds a little water standing in it. She smears the mud with a sort of sliding roll which effectively smooths and seals the surface against the passage of water. The next time it rains she will have a nice place to wallow, and the water will remain until it evaporates.

No self-respecting sow would try to make a wallow unless the site were mineral in character—entirely free from straw, corn cobs, or other organic debris. These latter materials would drain away the water, because the open, cellular structure of organic matter is conducive to moisture flow.

These farmers evidently had good hog wallow material, which was precisely what they did not want. They had it not only at the foot of the slope, but all over the surrounding watershed. Obviously, what they needed to do was the converse of the sow's problem; they must provide organic drainage for the surrounding slope so the water would not converge on the low ground. Their faith in tile, and possibly their firm, hard-headed American belief that the more a thing costs the more it is worth, kept them from thinking of this simple and inexpensive solution of their problem.

Water that falls on the upper reaches of a slope cannot possibly find its way to the lower ground if the intervening soil is absorbent. Really absorbent soil simply cannot conduct water over its surface. There are two forces operating to prevent its doing so, and the action of either is usually sufficient. The vertical pull of gravity is fully capable of pulling water into the soil, provided the surface has not been made impervious. And gravity is reinforced by the capillary pull of any absorbent surface. Let us suppose that a roof is covered with a half-inch pad of blotting-paper. How soon might we expect to see water dripping off the roof? Certainly not until the blotting-paper itself was completely saturated. The identical thought applies to any slope over which water is accustomed to run. If the water succeeds in reaching the lower ground, it does so only because the condition of the surface forces it to run off.

In this connection it is very interesting to recall the remarks of a prominent agriculturist with whom I was discussing this problem. I suggested that little water could get away from a " cove " soil,⁽¹⁾ and he agreed. He reinforced the thought with the information that he had seen cove soil on 90 per cent. slopes and had been unable—though he watched during a heavy rain—to observe any run-off.

If water will refuse to run off over a 90 per cent. slope covered with a layer of absorbent material, surely we have a clue that may help solve the run-off problem on the slight slopes we usually farm. If we can make the surface layers of soil absorbent to a sufficient depth, we certainly will not have to worry about run-off and erosion, just as nobody worried about these problems when the land was new. They were not problems then.

To put in a system of drain tile on land that had developed an apparent need for drainage is a matter of economic consequence. Tile costs a great deal of money. Its installation, whether properly done or not, is also expensive. And, at best, the results may be no more than the removal of symptoms of trouble which should be attacked by more appropriate means. Certainly, in view of the necessary investment involved in tile installations, some previous work designed to make the surrounding soil more porous would be advisable before the decision is made to put into the land an outlay of cash and labour which might easily equal the previous value of the land itself.

Nobody really knows whether it is possible to restore to the soil its original porosity. We do know that organic matter on the surface, as in the cove soils, does prevent practically all run-off; but we have no way of knowing whether it would be possible to work enough organic matter into a soil to make it take in all of the rainfall. We know, too, that the actual cost of growing a crop of rye and discing it into the ground would be a mere trifle when compared with the cost of installing tile. It is certainly true that ploughing a crop of rye into the soil does not decrease run-off; in fact, run-off is at its very worst on land that has been ploughed and lies bare because of having been ploughed.

Knowing all of these facts about the behaviour of water on the soil surface, it seems worth while as a preliminary to the major operation of tile drainage to test the possibility of curing the wet spots by preventing the run-off water from reaching them. The only way water can be prevented from finding low ground is to cause it to run into the surface where it falls. To cause an eroded soil to do this might require that several successive crops of green manure be disced in. Even that, if necessary, would be preferable economically to spending the money for tile; for if we can make all the water that falls on the land run into it, we will have done the perfect job of conserving the water supply.

Because there is urgent need for conserving water, any suggestion of additional tile installations should be viewed with suspicion. There are important reasons for this attitude:

(1)	In many parts of the country there is now a serious shortage of water during most of the year. Cities are enlarging the areas from which they draw their supply, taking in whole new watersheds. The water table in most farm communities is noticeably lower, for farm wells have had to be deepened in many instances in order to keep pace with a receding water table.
(2)	Droughts are becoming more common and more serious. Generally speaking this is true over most of the United States.

Both these conditions should be considered before one proceeds with plans to put in new tile drains. Each indicates that the reserve water supplies in most communities are too little instead of too large. It seems foolish to consider withdrawing additional water from places where there is already a shortage indicated both by the lowering water table and by the prevalence of droughts.

It should be remembered, too, that tile is a permanent exit for water from the soil. All water that reaches it will be led away. Tile may be put in for the sole purpose of removing in springtime a few hundred gallons of water from a low spot. It remains in place 365 days a year. It has absolutely no discretion as to what water to remove. It must remove needed water as freely as it drains away that which is surplus.

What of flood effects ? No single tile installation is going to influence flood height noticeably; but the combined outflow from all the tile drains on a given watershed does increase the freshets that follow heavy rains. Indeed, some open-textured soils, when subjected to heavy rains in spring before they have settled firmly from winter heaving, actually offer so little filtering resistance to the passage of the water that it is still muddy when it leaves the tile. This is eloquent testimony to the speed with which the rainfall—even though it enters the soil—may reach the streams to add to the destructiveness of floods. Such prompt elimination of the water which finds the tile drain after spring rains surely cannot be in the best interest either of the farmer on whose land it falls or of those whose farms it must inundate on its way to the sea.

Tile installation is considered so virtuous an act that the only question raised in connection with it is the farmer's ability to finance the purchase and laying expenses. This uncritical approach to the problem may be traced to the fact that early drainage projects often paid for themselves by means of the crops produced the very first season. These projects were designed to lower the actual water table in swamp land. Current proposed installations are expedient in character, being designed to correct trouble obviously caused by run-off.

When we realize that gravity is constantly tugging at the run-off water to drag it into the soil, the fact that all the water does not run in is proof that something serious has happened to the soil surface, for originally all soils were as absorbent as cove soils. The change is explainable solely by the loss of organic matter. The actual mechanics of the situation may prove more difficult to understand, because of human visual limitations.

Ants and other creeping things that belong in the soil surface recognize the changed condition. They are vitally affected by it. The disappearance of organic matter from the soil surface forces a change of habitat upon some of them. When, originally, the mineral particles of the soil were separated by fragments of organic matter in process of decay, these small forms of life were able to enter the surface quite readily because of its porous character. Once under the surface, they found both food and water in the organic matter itself. Many kinds of these denizens of the soil surface are now unable to penetrate the purely mineral surface because of its lack of porosity. They once aided natural drainage. Now they frequently cannot. It is not in our power to remedy the defect by artificial means, such as tile drainage.

We humans detect the presence of organic matter in the soil by the smudge caused by the presence of carbonized (partly decayed) material; though we cannot see the separate fragments, passageways afforded by its porosity permit the tiny mites of life that exist in and on the soil surface to travel about under-ground just as we travel by subway. Every protruding stem is to them another subway entrance to abundance of food and water. Because of the dependence of these small forms of life on decaying organic matter, the disappearance of the organic matter from our soils has caused a complete change in the fauna of the soil surface. The most casual comparison of biological conditions of the forest floor with those of the eroding land of our farms will show that one is teeming with a great variety of life while the other is almost devoid of it.

With the disappearance of the organic matter from a soil previously well supplied with it, then, we arrive at surface conditions just as truly desert in all essentials as the desert itself. Only the prevalence of a higher rainfall, reasonably well distributed throughout the year, prevents the pure mineral soils of the humid East from being as barren as are the desert soils of Arizona. Some of them are almost that barren in any case. When centipedes and lizards leave farm land, they do so in response to a process in Nature which might properly be called eviction. The soil may still show a little dark colour when the last of such forms of life disappear from it, but their departure means that the organic matter supply has been reduced to such an extent that the soil surface is no longer a suitable habitat. The eviction of minute forms of life sets the stage for those large problems of drainage with which this chapter deals. The remedy is to restore at once the organic condition of the soil and with it the teeming life which feeds upon it. This is organic balance, and it never tolerates the development of conditions which the drain tile is supposed to ameliorate.

Obviously, if the water is unable to move from the place where it falls, the wet spots in the low situations will disappear for lack of water to make them wet. And it is equally obvious that all engineering works now proposed as means of checking the damage done to the land by rainfall will be entirely unnecessary. Except in swamp areas, tile drains will be superfluous. And terraces, which are often more expensive than tile, may even be dispensed with.

Preliminary to any concerted action by governmental agencies to correct the present impervious condition of the soil surface, it would probably be a fine thing if every farmer would plug the outlets of most of his tile drains. This would give opportunity for a great deal of water that now floods the valleys to sink deep into the ground so that it could be withdrawn again by capillarity. Such a measure carried out by all the farmers on a given water-shed ought to prove important, too, in increasing the supply of water in the wells of the community. Many a farmer would like to be able to devote to crop-growing much of the time he is now bound to spend hauling water for his livestock. If he and all his neighbours would simply plug all the unnecessary lines of tile they have put in, they would probably discover that they would no longer need to haul water.

This, however, would be only one of a number of benefits. Among these, the increased supply of water available to crops is the most important. Thus the growth of plants could be increased, and the length of time during which crops suffer between rains could be reduced. There are other less obvious, but no less important benefits that will follow the plugging of tile lines. To avoid recurrence of wet spots, however, it would be well if the farmer would work a green manure crop into the soil surrounding these spots before he closes the tile outlet.

The sooner we make ancient history of many of our present farm practices the earlier we shall realize that the Garden of Eden, almost literally, lies under our feet almost anywhere on the earth that we care to step. We have not begun to tap the potentialities of the soil for producing crops.

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