708 SOILS: PBOPSETIES AND MANAGEMENT 



diverter inserted into the current, which diverts a definite 

 portion of the stream. This is called a divider. 



606. Amotmt of water to apply. — The amount of 

 water to apply to the soil at any one time depends on 

 (I) the nature and condition of the soil, (2) the supply of 

 water, (3) the crop, and (4) the season. In the main, 

 enough water should be applied to capillarily saturate 

 the soil to a depth of one foot and to increase the soil 

 moisture to a depth of three feet. A fairly dry, fine- 

 textured soil will effectively take the largest irrigation. 

 Some crops are more sensitive to water at one period of 

 growth than at another. Potatoes should mature in a 

 rather dry soil. The application of water at a single 

 irrigation should ordinarily be from four to eight inches. 

 In very hot weather it may be reduced to two or three 

 inches. In late fall or early spring, when the soil is 

 unoccupied, the application may be relatively larger 

 provided the soil is dry. 



Excessive irrigation is to be avoided. Wliile the total 

 yield increases with increase in the application of water 

 up to the maximum point, the unit production decreases.^ 

 The following brief table, calculated by Widtsoe from 

 actual yields of wheat, illustrates this point : — 





Thirty Acee-inches of Watee spread over 





1 acre 



2 acres 



3 acres 



4 acres 



6 acres 



Grain (bushels) 

 Straw (pounds) 



47.51 

 4532 



91.42 

 2908 



130.59 

 10256 



166.16 

 13204 



226.16 

 17916 



^Widtsoe, J. A. Tlie Production of Dry Matter with Dif- 

 ferent Quantities of Irrigation Water. Utah Agr. Exp. Sta., 

 Bnl No. 116, 1912, 



