DRAINAGE, in husbandry, is the art of carrying off water from the soil and subsoil of land by Means of open or closed drains or trenches—the term, however, is generally understood to apply to closed drains. By its means, the fertility of wet land has been greatly increased. When the drains are put in every 6 or 10 yards, it is called furrow or frequent draining.
The vast amount of capital which has been expended in D. within a quarter of a cen tury, attests its utility and necessity. Before the introduction of furrow draining, stiff and tenacious clays were of comparatively little value. They were cultivated at much expenditure of labor, and the crops which grew upon them were influenced to a great extent by the variations of the seasons. A system by which wet and worthless land could be rendered dry and valuable, was an improvement so patent to practical men, that we need not wonder at its general adoption.
D. by open ditches was no doubt the first mode of freeing' land from superfluous water. The Roman agricultural writers mention the good results arising from covered drains, which were formed of wood and other ,substances, which served so far to render the land dry. More than a century ago, a large extent of clay-land was drained at narrow intervals in Norfolk and Essex, by putting in brush-wood and even straw in the bottom of the drains. The progress of draining, which is now regarded in many soils as essential to economic culture, was slow and partial, until Mr. Smith, of Deanston (well on in the 19th c.) reduced the practice to a system, and showed the principles upon which its efficiency depended. Through the exertions of this advocate, furrow draining soon became a sine gad non in the culture of clay-soils, or indeed any soil, in moist climates.
Practical men consider the line of greatest fall, or quickest descent, as the best for cutting drains in a field. The smaller drains are usually conducted into larger or main drains, instead of each discharging its quota of water into the open ditch. This is ren dered necessary, as the mouths of the smaller drains would be more liable to be choked up by the growth of weeds; while the collecting of water into main drains secures a fuller flow to sweep out any matters which might accumulate where the discharge was small. Moreover, the less of the action of the air in the drains, the more efficient they
are.
The most efficient, and at the same time cheaply cut drain, is made so that a pipe of a cylindrical form may be laid along the bottom, which need be of no greater width than what is necessary to allow of the pipes being properly laid.
Drains of this form are cut with a set of spades which are of different widths—the broader being used for taking out the top, and the narrowest for the bottom. The one which cuts the last spit is called the bottoming tool, and its introduction has effected a considerable saving in cutting drains. The pick has often to be used, too, where the subsoil is hard. The cutting of drains is heavy, crushing work. Men employed at this sort of labor are generally paid by the piece; and a professional will make rather above the ordinary rate of laborer's pay. One not accustomed to drain-cutting finds it for some time very hard labor; but experienced hands prefer draining to trenching.
Before the general use of pipes, stones were the common materials with which drains were formed. Mr. Smith recommended that they should be broken so small, that they might pass through a ring two inches and half in diameter. From nine inches to a foot in depths was the quantity which was commonly put in. Where stones can be easily got, they are still preferred to tiles, as cheaper, and if well put in, more efficient and durable. The best plan is to set a pretty large block at each side of the bottom of the drain, and then use a third as a sort of wedge. A coating of smaller stones is surmounted by some turf and the muck.
When tiles and pipes were first used, it was even thought necessary to have some gravel, or small stones, placed above them in the drains, for the purpose of the water to find its way into them. It was soon found, however, that tile drains were quite as efficient without any stones or gravel; and that they were less liable to be choked up, as the clay or earth acted as a filter in preventing the intrusion of any kind of solid matter.