THE EFFECT OF CULTIVATION 99 



ductivity of the soil is more rapidly decreased by corn than 

 by grain crops. These two facts seem somewhat contrary 

 but when studied prove to be just what might reasonably 

 be expected. 



118. Cultivation Liberates Plant Food. As stated else- 

 where, plant food is made soluble or available for plants very 

 largely by the decomposition of vegetable matter. Vege- 

 table matter can decompose or rot only when in the presence 



Fig. 33. Ear of Boone County, White corn. A popular white dent variety 

 in southern Indiana, Illinois, and Iowa and northern Missouri. Grown to. 

 some extent in the South. 



of air and moisture. Hay in the mow does not rot because it 

 is kept dry. Silage in the silo does not rot because air is 

 kept away from it. Vegetable matter in the soil, that is, 

 manure and the roots and stems of plants, will naturally 

 decompose more rapidly if proper conditions of air and 

 moisture are maintained than when such conditions are not 

 present. 



