126 



THE ESSENTIALS OF AGRICULTURE 



Where sufficient water is available for irrigation in the arid 

 parts of the country, farming under irrigation is very profitable, as 

 it enables one to control the moisture supply in the soil to better 

 advantage than where one must depend upon rainfall. Even 

 when all the available water is used, only about 10 per cent of 

 the total area of the dry lands of the United States can ever be 

 irrigated. 



III. DRY FARMING 



153. What is dry farming ? The term dry farming is applied 

 to a system in use in regions where the moisture supply is less 

 than that ordinarily used in crop growth. Plants cannot be grown 



FIG. 53. Distributing water 



Part of the water is diverted through lateral ditches to the fields. (Photograph from 

 Office of Experiment Stations, United States Department of Agriculture) 



without water, but it is possible to grow them with a limited 

 supply when drought-resisting varieties are selected, and when 

 the rain that falls is caught and conserved in the soil. In some 

 areas the rainfall is not sufficient to grow a profitable crop each 

 season, even when these precautions are taken. In such cases 

 the moisture that falls through two years is stored in the soil 

 for the growth of one crop. Dry farming has been practiced in 



