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Show TWO METHODS OF IRRIGATION Underflow System Is Quite Different From Subirrigation Advantages of the Former. (By E. .1. WH'KSOX. M. A., Professor of-AKi-kultm-e. California Agricultural Experiment Station.) Subirrigation is the application of water under the surface by a system of conduits. It has received so much thought and outlay and has returned so little satisfaction that it must be looked upon as a horticultural ignis fatuus, and only a passing reference need be given to it. Various available publications describe its different phases. It seems fair to conclude that satisfactory growth is secured with 1 less water by subirrigation than by J surface distribution, but it is done at an outlay which is unwarranted either by the cost of water or by the value of the crop. Results of greenhouse experiments ex-periments are more satisfactory than those from open-air work. Even if even distribution could be had from any arrangement . of underground pipes, which seems doubtful In view of wide experience, it sUll remains true that for shallow-rooting plants In open soils the water is applied at too low a level. It also appears that the escape from the surface cultivation Is of doubtful advantage, contrary to the claims of advocates of subirrigation, and that thorough surface stirring, which is an Indispensable accompaniment of surface sur-face irrigation, is worth all It costs through the superior thrift which It induces. It seems a fair conclusion , from present knowledge that subirri- f gation is practically unattainable because be-cause of cost, inequality of distribution, distribu-tion, etc., and possibly would be undesirable unde-sirable even if these prohibitions were removed. Underflow irrigation is quite different differ-ent from subirrigation, though the former for-mer often goes in local parlance as "natural subirrigation." Underflow is a natural movement of water through the subsoil outward from streams or downward from catchment areas toward to-ward the country drainage. Underflow irrigation consists in reinforcing this flow, or in imitating it by bringing . water "to follow the same course of distribution. It is an available method, first, where the ground water is naturally near the surface and irrigation water is easily obtained in large quantities; second, where an open soil through which water spreads readily is found resting upon an impervious hardpan, or slightly pervious clay, which prevents pre-vents loss of water by percolation. In both of these, conditions the method of irrigation is the same, viz, to open deep furrows at considerable distances apart and keep them filled with water : for a considerable time, so that it may soak away in large quantities. The addition will in the first case raise the ground water ao that it will rise by capillarity to the plant roots; in the second case the irrigation water wa-ter will spread through the free soil, flowing along the surface of the hard-pan hard-pan or clay, and will thus become available to plant roots. These methods meth-ods are most apt to be useful with deep rooting trees and vegetables, but they are also used, where the conditions are favorable, for grains and garden crops. ' |