8 CLOVERS 



ral period of the life of the plant lessens and vice 

 versa. Consequently, the medium red variety, the 

 mammoth, the crimson, the Japan and the burr 

 varieties stand high in such adaptation. The alsike, 

 living longer, is lower in its adaptation, and alfalfa, 

 because of its long life, stands lowest in this respect. 

 The small, white variety is almost invariably grown 

 or found growing spontaneously along with grasses, 

 hence no definite place has been or can be assigned 

 to it in the rotation. Sweet clover being regarded 

 by many as a weed has not had any place assigned to 

 it in a regular rotation, although in certain localities 

 it may yet be grown for purposes of soil renovation. 

 (See page 306.) 



All these crops are leguminous without any excep- 

 tion. This fact is of great significance where crops 

 can be rotated. They have power to gather nitrogen 

 from the air and store it in the soil in tubercles 

 which form on their roots, in all soils in which they 

 produce a vigorous growth. This fact indicates 

 where they should come in the rotation. They 

 should be grown with a view to gather food for. 

 other crops made to follow them, which -have not the 

 same power. They should, therefore, be made to 

 precede such , crops as the small cereals, com, the 

 sorghums, the millets and cotton. But since these 

 clover plants have the power to bring nitrogen from 

 the air, it must not be supposed that they will grow 

 with sufficient vigor in soils destitute of this element. 

 They must be able to appropriate enough from the 

 seed soil to give them a good start before they can 

 draw nitrogen from the air, hence, though they ma}^ 



