42 



THE BOOK OF CORN 



sections of the United States for increasing the avail- 

 able supply of nitrogen in the soil. These crops not 

 only supply nitrogen much more cheaply than any 

 form of commercial fertilizers, but they are also 

 valuable forage crops. They send their roots deep into 

 the soil, and improve the mechanical condition of the 

 land and by means of their extensive root systems 

 bring plant food from the subsoil to the surface soil, 

 where it may be used by future crops. The roots of 

 the leguminous plants decay and add large amounts 



Fig 14— Samples of Clover 



Taken from equal areas; different methods of seeding 



of humus to the soil, which is an important factor in 

 maintaining favorable physical and bacteriological 

 conditions. 



Clover has been grown in this country as a part 

 of the crop rotation for many years, but not until the 

 last fifteen years has its value as a soil fertilizer been 

 fully appreciated. There are several varieties, adapted 



