24 DRY-FARMING 



pheric precipitation per year are not safe for dry- 

 farm purposes. What the future will show in the 

 reclamation of these deserts, without irrigation, is 

 yet conjectural. 



Arid, semiarid, and sub-humid 



Before proceeding to an examination of the areas 

 in the United States subject to the methods of dry- 

 farming, it may be well to define somewhat more 

 clearly the terms ordinarily used in the description 

 of the great territory involved in the discussion. 



The states lying west of the 100th meridian are 

 loosely spoken of as arid, semiarid, or sub-humid 

 states. For commercial purposes no state wants to 

 be classed as arid and to suffer under the handicap 

 of advertised aridity. The annual rainfall of these 

 states ranges from about 3 to over 30 inches. 



In order to arrive at greater definiteness, it may 

 be well to assign definite rainfall values to the ordi- 

 narily used descriptive terms of the region in question. 

 It is proposed, therefore, that districts receiving 

 less than 10 inches of atmospheric precipitation 

 annually, be designated arid; those receiving between 

 10 and 20 inches, semiarid; those receiving between 

 20 and 30 inches, sub-humid, and those receiving over 

 30 inches, humid. It is admitted that even such a 

 classification is arbitrary, since aridity does not alone 

 depend upon the rainfall, and even under such a 



