286 DRY-FARMING 



in the soils of the Great Plains and from three to four 

 times as much as is found in the soils of the Great 

 Basin and the High Plateaus. It may be assumed, 

 therefore, that the Indian Head soil was peculiarly 

 liable to nitrogen losses. Headden, in an investi- 

 gation of the nitrogen content of Colorado soils, 

 has come to the conclusion that arid conditions, like 

 those of Colorado, favor the direct accumulation 

 of nitrogen in soils. All in all, the uncUminished 

 crop yield and the composition of the cultivated 

 fields lead to the belief that soil-fertility ]3roblems 

 under dr3'-farm conditions are widely different from 

 the old well-known prol^lems under humid concUtions. 



Reasons for dry-farm ing fertility 



It is not really difficult to undei-stand why the 

 yields and, apparently, the fertility of dry-farms 

 have continued to increase during the period of re- 

 corded dry-farm history — nearly half a century. 



First, the intrinsic fertility of arid as comjjared with 

 humid soils is very high. (See Chapter V.) The 

 production and removal of many successive bountiful 

 crops would not have as marked an effect on arid as 

 on humid soils, for both yield and composition change 

 more slowly on fertile S(jils. The natural extraordi- 

 narily high fertility of dry-farm soils explains, there- 

 fore, primarily and chiefly, the increasing yields on 

 dry-farm soils that receive proper cultivation. 



