DRY-FARMING ZONES 



haust the fertility of any soil. 1 It is 

 therefore surprising to learn that in some 

 of the older valleys of the Great Basin 

 where wheat has been grown for close on 

 half a century that there seems to be no 

 trace of diminished fertility. Indeed, 

 some authorities say that those fields are 

 producing heavier crops than when first 

 plowed. The reason of this sustained 

 yield is made plain when we remember 

 that most of the grain of the dry -lands of 

 the Great Basin is "headed" instead of 

 being cut with a binder, and where such a 

 large amount of straw is plowed under 

 there is probably no real reduction in the 

 humus of the soil. But even where the 

 binder is used, it is more than likely that 

 the surface cultivation which is so widely 

 practised in this region for the conserva- 

 tion of moisture also encourages the 



1 This has been shown in a striking manner in the State 

 of Minnesota, where the continuous production of wheat 

 has worn out the once rich soils of that region. 



177 



