CHAPTER X 

 THE METHOD OF IRRIGATION 



THE method of irrigation determines greatly the duty 

 of water and the profitableness of irrigation. The con- 

 siderable labor which always attends the application of 

 water to land is one of the big charges to be made against 

 irrigation, and one that must be made as low as possible. 

 Besides, the method of irrigation frequently affects, 

 directly, the degree to which plants may use the water 

 applied. 



There are only two general methods of applying irri- 

 gation water; first, irrigation above ground and, second, 

 irrigation below ground. Each of the two methods appears 

 under several variations and possesses a special advantage. 

 In practice, the method of applying water above ground 

 is the only one in general use. 



118. Sub-surface irrigation. The application of 

 irrigation water from below, or sub-surface irrigation, has 

 the advantage that water so applied is not subjected to 

 such direct evaporation from the surface as of necessity 

 accompanies surface irrigation. When water is scarce, 

 it is especially of great importance to reduce such evapora- 

 tion. For this purpose, sub-irrigation seems to be the 

 method that should be employed. 



It should, however, be kept in mind that the suc- 

 cessive wetting and drying of the top soil, which accom- 

 panies surface irrigation, benefits crops and enables them 

 to produce dry matter with least water, and often this 



(189) 



