IRRIGATION PRACTICE AND HIGHWAYS 313 



1. On fairly retentive soils a winter-growing 

 short-season grain like barley or a short-season wheat 

 may make a, good grain crop with ten inches of 

 rainfall evenly distributed during the rainy season. 

 However, the crop will be surer and larger if the 

 crop is irrigated either before sowing or during 

 growth. The profit will be determined by the sea- 

 sonal distribution of rainfall and the selling-price 

 of the crop. 



2. On a deep fairly retentive soil a deep-rooting 

 plant like alfalfa will give from one to three cut- 

 tings of hay with fifteen to twenty inches of rain- 

 fall, but will yield from five to ten cuttings by adding 

 the same amount or more of water by irrigation dur- 

 ing the season of continued growing temperature of 

 the long summer and autumn. 



3. On an average soil a drought-resistant plant 

 like a grain sorghum will make a good growth of 

 forage with fifteen inches of rainfall conserved by 

 spring tillage for planting when the local frost-free 

 date is reached. With a retentive soil and continued 

 summer tillage, the same plant will make a grain 

 crop. On a less retentive soil a heavier grain crop, 

 or continued cutting of forage, may depend on sum- 

 mer irrigation. 



4. With fifteen inches of rainfall on a fine re- 

 tentive loam soil, deciduous fruit-trees and grape- 

 vines can be brought along to bearing age by good 

 winter and summer tillage, but the same trees or 

 vines will need a total of twenty to thirty inches of 

 water, either from rainfall or irrigation, when in 



