2 to 3 acres 3-ineh files.
4 to 6 acres 4-inch tiles.
Mains to to 15 acres 6-inch tiles.
10 to 40 acres 8-inch tiles.
40 to zoo acres to-inch tiles.
The tools used in the formation of drains are few in number, and of a very simple description. They consist of a set of spades—generally three of different sizes—gradually diminishing in width to suit the different parts of drains. For taking out the last narrow spit, to form the seat for the draining pipe, long, narrow, triangularly shaped spades, called bottoming tools, are used.' There are also scoops of various widths, nished with long handles, and rounded or flat tened in the soles according as they are required to finish the bottom of the drain for the recep tion of stones, a horse-shoe tile and sole, or a draining pipe. For the purpose of laying pipes in minor and deep drains an instrument called a pipe-layer, consisting of a short rod' attached at a right angle to a long handle, which enables the workman to lay the pipes without going into the drain or reaching the bottom with his hand,.is employed. Where the subsoil is strong or indurated, a hand-pick or a foot-pick is required to loosen it before it can be shoveled out.
Benefits of Drainage.— The following are among the benefits arising from thorough drain age: 1. Removal of superfluous water. Not only is the standing water at the surface carried off, but the water-table is lowered, increasing the depth of soil. Energy that would otherwise be required for evaporation of water is thus saved for the immediate benefit of vegetation.
Improves soil texture. Drained soils are more friable, less lumpy, offer less resistance to plant roots, and are of better texture in every way, than undrained soils.
3. Increases root pasturage. Agricultural literature is full of testimony to the benefits of deep tillage. The deeper the soil is stirred the greater its productiveness. Plant roots pene trate to a depth of several feet under favorable conditions such as drainage supplies. Root pas turage is also increased by the increase of sur face presented by the much finer division of soil particles.
4. Increases soil fertility. It prevents loss of fertility by water passing over the surface. It adds to the fertility by sending summer showers down through the soil, instead of over them, enabling the crop to use the nitric acid and ammonia brought down. It increases the effect of manures by bringing them more quickly into solution and into more intimate contact with plant roots; and it increases the absorptive power of soils for fertilizing matter in solution.
5. Makes tillage easier. By clearing up waste places and covering ditches the field is brought into better shape for use of labor-sav ing machinery. Waste land is reduced, and the better texture of soil, its finer tilth and greater friability decrease draft and increase the effec tiveness of tillage implements.
6. Lengthens the growing season for crops. Frost comes out earlier in the spring and the land becomes earlier warmed. Evaporation lowers temperature, but drainage removes water without evaporation. A well-drained soil is 12°
to 14° F. warmer than a soil full of stagnant water. The sun's rays penetrate to a greater depth, and warm summer showers have a greater effect. The season is lengthened by adding the days in summer after heavy rains when undrained soils cannot be tilled, and crops come to a standstill ; coming of the autumn is delayed until later, and the soils are warmer throughout the season.
7. Assists disintegration. Frosts penetrate deeper in winter in drained soils, assisting in unlocking the stores of mineral plant food. More surface is exposed to the action of disin tegrating agents, and the soil presents conditions more favorable to their action throughout the season.
8. Favors nitrification and bacterial action. Plants are largely dependent on the decomposi tion of organic matter in the soil for their sup ply of nitrogen. This change is brought about by the action of ferments or bacteria which thrive only under certain conditions of tempera ture and moisture. Drainage supplies the most favorable condition for their development;. it also favors the growth of the nitro-bacteria found on the roots of leguminous plants, which by their means appropriate free nitrogen from the air.
9. Prevents heaving. The effect of stool-ice in throwing out young plants in winter is often to diminish seriously and even destroy the crop. Drainage dries up the surface soil and prevents the formation of stool-ice.
10. Lessens washing and diminishes vio lence of floods. By increasing the absorptive power of the soil less water is left to pass over the surface in a rainy season, so that washing and floods are materially lessened.
11. Improves the quantity and quality of crops. That the yield of crops is much greater on drained soils hardly needs to be substan tiated, while the more vigorous growth of plants renders them much less susceptible to the at tacks of fungi or the ravages of insects, thus Improving the quality. Rust, mildew, blight, etc., are much less prevalent in crops on drained soils.
12. Diminishes the effect of drought. By making the season earlier tillage can begin sooner save moisture from wasting. Plants are given a bettter start and root deeper, thus being less affected by, a dry surface. The soil is deeper and has greater capacity for moisture. Its finer texture nearly doubles its capillary power over undrained soils. Ordinarily drain age increases the capillary power of soils from 25 to 40 per cent. A drained soil holds water like a sponge, an undrained clay like a dish.
13. Healthfulness improved. So well known is this fact that large towns have undertaken the drainage of adjacent swamps at public ex pense to render the region more healthful. See AGRICULTURE; SANITARY ENGINEERING; SANITARY SCIENCE and PUBLIC HEALTH.
Among the later authoritative books on drainage, Chamberlain, (Tile part, (1..and Draining' ; French, 'Farm Drain ing) ; Miles, (Land Draining); Waring, (Drain ing for Profit and Health) ; Jeffrey, Book of Land Drainage) (1916).