190 THE BOOK OF ALFALFA 



tities of nitrogen. A field cropped for years in corn or 

 wheat will come to have too little nitrogen for the pro- 

 duction of a profitable crop. Alfalfa, as has already been 

 stated, after the first few months of its life obtains its 

 whole supply of nitrogen from the air ; in fact, more than 

 it really needs. As a soil improver it possesses at least 

 five valuable properties : 



1. It gathers nitrogen from the air for its own main- 

 tenance and a surplus that is constantly being added to 

 the soil. 



2. It is a deep feeder and its roots penetrate the earth 

 to extraordinary depths, drawing toward the surface and 

 utilizing moisture and valuable mineral elements that 

 other crops would never reach, leaving the desirable 

 elements there for future crops, of whatever kinds. 



3. By capillarity, these roots and rootlets draw up 

 moisture from below the surface until it modifies the 

 very top soil, changing wonderfully the nature of the 

 field. The analysis of a cubic foot of earth of a flourish- 

 ing alfalfa field shows a marvelous change in moisture 

 content since the sowing. 



4. The mere mechanical effect of the extensive root 

 system can scarcely be over-estimated. As soon as ger- 

 mination begins the plant starts its tiny roots downward 

 on the search for moisture. Roots four feet long have 

 been found on alfalfa but four months old; roots nine 

 feet long have been found below alfalfa but nine months 

 old. After the taproot reaches a few inches below the 

 surface, it sends out smaller roots that have a lateral 

 growth of but a few inches, when they too, take a down- 

 ward course for moisture and for mineral elements needed 



