DISTRICTS OF DRY-FARM SOILS 77 



sulphate, or crystals of the ordinary land plaster. 

 The fertility of the soils, however, is high, and when 

 they are properly cultivated, they yield large and 

 excehent crops. 



California district. — The fifth soil district lies 

 in California in the basin of the Sacramento and 

 San Joaquin rivers. The soils are of the typical 

 arid kind of high fertility and great lasting powers. 

 The}^ represent some of the most valuable dry-farm 

 districts of the West. These soils have been studied 

 in detail by Hilgard. 



Dry-farming in the five districts. — It is interesting 

 to note that in all of these five great soil districts 

 dry-farming has been tried with great success. 

 Even in the Great Basin and the Colorado River 

 districts, where extreme desert conditions often 

 prevail and where the rainfall is slight, it has been 

 found possible to laroduce profitable crops without 

 irrigation. It is unfortunate that the study of the 

 dry-farming territory of the United States has not 

 progressed far enough to ])ermit a comjjrehensive 

 and correct mapping of its soils. Our knowledge 

 of this subject is, at the best, fragmentary. We 

 know, however, with certainty that the properties 

 which characterize arid soils, as desciibed in this 

 chapter, are possessed by the soils of the dry-fanning 

 territory, including the five great districts just 

 enumerated. The characteristics of arid soils in- 

 crease as the rainfall decreases and other conditions 



