As to the importance of securing the outlets, and the manner of doing it, we have spoken particularly elsewhere.
And here, again, we will remind the beginner, of the necessity of making and preserving accurate plans of the work, so that every drain may be at any time found by measurement. After a single rotation, it is frequently utterly impossible to perceive upon the surface any indication of the line of the drains.
In this connection, it may be well perhaps to remind the reader, that whatever arrangements are made as to silt-basins, or peep-holes, must be included in the general plan, and executed as the work proceeds.
CHAPTER XIII
EFFECTS OF DRAINAGE UPON THE CONDITION OF THE SOIL.
Drainage deepens the Soil, and gives the roots a larger pasture.—Cobbett's Lucerne 30 feet deep.—Mechi's Parsnips 13 feet long!—Drainage promotes Pulverization.—Prevents Surface-Washing.—Lengthens the Season.—Prevents Freezing out.—Dispenses with Open Ditches.—Saves 25 per cent. of Labor.—Promotes absorption of Fertilizing Substances from the Air.—Supplies Air to the Roots.—Drains run before Rain; so do some Springs.—Drainage warms the Soil.—Corn sprouts at 55°; Rye on Ice.—Cold from Evaporation.—Heat will not pass downward in Water.—Count Rumford's Experiments with Hot Water on Ice.—Aeration of Soil by Drains.
The benefits which high-lands, as we ordinarily call them, in distinction from swamp or flowed lands, derive from drainage, may be arranged in two classes, mechanical and chemical; though it is not easy, nor, indeed, is it important, to maintain this distinction in all points. Among those which partake rather of the nature of mechanical changes, are the following:
Drainage deepens the soil. Every one who has attempted to raise deep-rooted vegetables upon half-drained swamp-land, has observed the utter impossibility of inducing them to extend downward their usual length. Parsnips and carrots, on such land, frequently grow large at the top, but divide into numerous small fibres just below the surface, and spread in all directions. No root, except those of aquatic plants, will grow in stagnant water. If, therefore, it is of any advantage to have a deep, rather than a shallow soil, it is manifestly necessary, from this consideration alone, to lower the line of standing water, at least, to the extent to which the roots of our cultivated crops descend. A deep soil is better than a shallow one, because it furnishes a more extensive feeding-ground for the roots. The elements of nutrition, which the plant finds in the soil, are not all upon the surface. Many of them are washed down by the rains into the subsoil, and some are found in the decomposing rocks themselves. These, the plants, by a sort of instinct, search out and find, as well in the depths of the earth as at its surface, if no obstacle opposes. By striking deep roots again, the plants stand more firmly in the earth, so that they are not so readily drawn out, or shaken by the winds. Indeed, every one knows that a soil two feet deep is better than one a foot deep; and market-gardeners and nursery-men show, by their practice, that they know, if others do not, that a trenched soil three feet deep is better than one of any less depth. We all know that Indian corn, in a dry soil, sends down its rootlets two feet or more, as well as most of the grasses. Cobbett says: "The lucerne will send its roots thirty feet into a dry bottom!" The Chinese yam, recently introduced, grows downward two or three feet. The digging of an acre of such a crop, by the way, on New England soil generally, would require a corps of sappers and miners, especially when we consider that the yam grows largest end downward. However, the yam may prove a valuable acquisition to the country. Every inch of additional soil gives 100 tons of active soil per acre.
Says Mr. Denton:
"I have evidence now before me, that the roots of the wheat plant, the mangold wurzel, the cabbage, and the white turnip, frequently descend into the soil to the depth of three feet. I have myself traced the roots of wheat nine feet deep. I have discovered the roots of perennial grasses in drains four feet deep; and I may refer to Mr. Mercer, of Newton, in Lancashire, who has traced the roots of rye grass running for many feet along a small pipe-drain, after descending four feet through the soil. Mr. Hetley, of Orton, assures me that he discovered the roots of the mangolds, in a recently made drain, five feet deep; and the late Sir John Conroy had many newly-made drains, four feet deep, stopped by the roots of the same plants."
Mr. Sheriff Mechi's parsnips, however, distance anything in the way of deep rooting that has yet been recorded. The Sheriff is a very deep drainer, and an enthusiast in agriculture, and Nature seems to delight to humor his tastes, by performing a great many experiments at his famous place called Tiptree Hall. He stated, at a public meeting, that, in his neighborhood, where a crop of parsnips was growing on the edge of a clay pit, the roots were observed to descend 13 feet 6 inches; in fact, the whole depth to which this pit had once been filled up!