SAVING WATER BY CULTIVATION 



55 



ties of water that may be lost from the soil by evapora- 

 tion. The magnitude of such losses is well shown in the 

 following typical results taken from the Utah work. The 

 soil at the beginning of each test contained practically 

 17.5 per cent of water. 



During the first seven days after irrigation, a quan- 

 tity of water equivalent to nearly 1.5 inches was lifted 

 from the soil by the power of the sunshine; during the 

 first fourteen days, nearly 2 inches, and, during the first 

 twenty-one days about 2% inches. Fortier and Beckett 

 found that during a twenty-eight-day period after irri- 

 gation a non-cultivated soil lost 2.13 inches of water, of 

 which about .8 of an inch or nearly 40 per cent was lost 

 during the first three days after irrigation, before culti- 

 vation could begin. Such great losses in an arid section 

 justify every effort of the farmer to conserve the soil 

 moisture by cultivation, and it should be done as early 

 as possible so that the water saving may be large. 



39. Depth of cultivation. The depth to which a soil 

 is cultivated, that is, the thickness of the soil mulch 

 produced, determines the rate of evaporation and there- 

 fore the quantity of soil moisture that may be saved. 

 This is only to be expected, for the thicker the dry mulch 

 above the moist soil from which evaporation proceeds, 

 the greater is the hindrance offered to the diffusion of 



