Drainage

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Drainage

However high and apparently dry a situation may appear, it is quite possible that it requires to be drained. The object of draining is not only to get rid of superfluous moisture, but also to prevent the little there may be from remaining stagnant.

It is quite a common occurrence to find a piece of ground that is never too wet, but which is, nevertheless, sour and unfitted for the cultivation of delicate flowers. It should, therefore, be the first care of the florist to make drains from the highest part of the ground to the lowest, three feet from the surface, dug in a V shape; and if there be no outlet at the lowest part, to dig a hole, or well, or pond, into which all these should lead, even when there is no apparent means of getting rid of the water.

At the bottom of these drains, along the narrowest part below the shoulders A A, a row of common 2-inch earthen pipes may be placed, end to end, and covered up again with the soil. These are too deep to cause any danger of disturbance in ordinary operations ; and the effect is to let air into the soil, if there be no surplus moisture : and to prevent the lodgment of water anywhere, a distance of about a rod apart, in parallel lines, will be sufficiently close for the drains, and a larger drain along the bottom, or a ditch, may lead at once to the outlet or the receptacle for the water.

Suppose, however, the soil is really surcharged with water, and there is no place but the pond made for the purpose into which this water can pass, and suppose, while we are imagining evils, that this pond or hole fills higher than the bottoms of the drains, it is obvious, in such cases, that the drains cannot empty themselves. Still, even such drains are of use ; if they can only dischaige all the water in the driest season, immense good is done by them. If the pond be not too large, a garden-engine may be set to work to lower the water by throwing it over the surface ; and although it may fill as fast as the water is taken away, there is a circulation of water going on in the soil, instead of moisture being stagnant, and the ground made sour.

The rationale of drainage is thus explained by Mr. D. T. Fish. "Drainage," he says, "as popularly misunderstood, means the art of laying land dry. This, however, is a very imperfect definition, both of its theoretical principles and practical results.

Paradoxical as it may appear, drainage is almost as useful in keeping land moist as in laying it dry. Its proper function is to maintain the soil in the best possible hygrometrical condition for the development of vegetable life. Drainage has also a powerful influence in altering the texture of soils. It enriches their plant-feeding capabilities, elevates their temperature, and improves the general climate of a whole district, by increasing its temperature, and removing unhealthy exhalations. It lays land dry, by removing superfluous water ; it keeps it moist, by increasing its power of resisting the force of evaporation ; it alters the texture, by the conduction of water, and by filling the interstices previously occupied by that fluid with atmospheric air ; it enriches the soil, by separating carbonic acid gas and ammonia from the atmosphere, and by facilitating the decomposition, absorption, and amalgamation of liquid and solid manures. It heightens the temperature of the earth, by husbanding its heat, and surrounding it with an envelope of comparatively dry air, and by substituting the air for water withdrawn through the interstices of the soil ; for while the tendency of excessive mois ture in the soil is to bind the whole mass into an almost solid substance, the tendency of air is to separate its particles into atoms, and render it porous : and the more porous a soil is, the greater is its power of resisting evaporation. For this reason, porous soils are more moist in hot weather than those of a more tenacious character.

" Drainage enriches soils in another way. All rain-water is more or less charged with carbonic acid gas and ammonia. Now, the larger the quantity of rain-water that passes through the soil, the greater will be the amount of these gases brought in contact with the roots of plants. Nor is this all : solid manures of the richest quality are comparatively useless on wet, heavy soils ; for while a certain amount of moisture is essential to the decomposition of manures, an excess arrests the process, and all the most soluble portions are washed out long before it is sufficiently decomposed to enter into the composition of plants. Judicious drainage, therefore, places the soil in a proper hygrometrical condition for performing its important functions."