FARM IRRIGATION 279 



crops of grains are literally blown out of the ground 

 after they are 3 to 5 inches high, their roots being 

 uncovered by the blowing away of 2 or 3 inches of 

 soil. Even slight barriers, as fences, lessen the 

 injury from wind for a distance of several hundred 

 feet to leeward. Lombardy poplars, cottonwoods 

 and locusts are commonly used for high windbreaks, 

 and Russian mulberry and the shrubby Artemisia 

 for low hedges. A cottonwood windbreak 40 feet 

 high has a beneficial influence to a distance of 

 650 feet to the leeward, preventing the soil from 

 drying out rapidly and from drifting. 



In the plains states where these conditions prevail, 

 windbreaks should always be provided ; they are es- 

 pecially needed in the sukhumid sections wnere irri- 

 gation is not possible, and the rainfall is scanty. 

 The plants of a windbreak do steal much moisture 

 from the adjacent land, but in windy sections they 

 save much more than they steal, by keeping drying 

 winds from hugging the ground. Broad fields 

 should be avoided and, if possible, a system of 

 rotation should be adopted that will keep fields in 

 alternate strips of grass or clover and tilled land. 



