THE DOMAIN FOR DRY FARMING 57 



of the state, the precipitation is more than 20 inches and 

 also in a narrow strip covering all the eastern border. In 

 some of the south central counties it is less than 10 inches 

 and in other parts of the state from 10 to 20 inches. 



In southern Alberta, southern Saskatchewan and 

 southwestern Manitoba, the precipitation is not far dif- 

 ferent from the same in the states of Dakota and Mon- 

 tana, which border on them, that is, it runs from about 

 12 to 18 inches. One or two degrees north from the 

 boundary it increases, and the increase is virtually as the 

 latitude rises. Evidence of such increase is seen in the 

 increase of tree growth. 



The season of precipitation. The season at which 

 the precipitation falls greatly influences the character of 

 the production. When the bulk of the rain falls in the 

 winter, autumn-sown crops can be grown with the best 

 success, since they get virtually the full benefit of the 

 precipitation, and they mature before the driest portion of 

 the year. When it falls in the spring months, spring 

 cereals may be more successfully grown. When it falls in 

 the summer months, the problem becomes more compli- 

 cated. 



In the Great Plains area the bulk of the precipitation 

 comes in the growing season; that is, in the months of 

 April, May, June and July. This so far is greatly 

 in favor of the growing crops, but the loss from evapora- 

 tion is greater than when much of the rain comes in the 

 winter. In some areas nearly half the precipitation 

 comes in June and July. In New Mexico and the dry 

 portions of Oklahama and Texas, the heaviest pre- 

 cipitation occurs in July and August. 



In the Inter-mountain states the precipitation is also 

 the heaviest in the spring months, but it is more evenly 

 distributed throughout the year, especially in the west- 

 ern portions of the same. This so far is favorable to the 

 production of both winter and spring crops. 



