94 



FIELD CROPS 



decompose more rapidly if proper conditions of air and mois- 

 ture are maintained than when they are not present. 



The corn crop is commonly cultivated throughout the 

 growing season. This cultivation aerates the soil and con- 

 serves moisture, hence decomposition takes place more 

 rapidly in a cultivated field than in a field that is not culti- 



Figure 35. — 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. 



vated. This rapid decomposition caused by cultivation 

 liberates large quantities of plant food. On this account, 

 planting a field to corn stimulates the liberation of plant 

 food and naturally leaves the soil richer in available plant 

 food for succeeding crops. This may easily account for 

 the larger yields which usually follow cropping a field for 

 one year to corn. It is evident, however, that if the field is 

 planted to corn year after year, the supply of vegetable mat- 

 ter will be quite rapidly depleted, so that the soil will soon 

 fail to respond to the stimulation of cultivation. Thus, 

 when a field is planted for a number of years in succession, 

 it rapidly decreases in productivity. 



