80 FIELD CROPS 



92. Depth of Cultivation. It is impossible to state any 

 arbitrary depth at which it is desirable to cultivate corn. 

 The object of the cultivation should be to leave the soil in a 

 loose, mellow condition on the surface and to destroy any 

 weeds that may be growing, with as little injury as possible 

 to the corn roots. Anyone may convince himself, by careful 

 observation, that the roots of corn quite thoroughly occupy 

 the entire soil area between the rows by the time the plants 

 are 12 to 15 inches high (Fig. 16). Since the roots are the 

 chief means the plant has of obtaining plant food and mois- 

 ture, it is plain that to injure any of these roots lessens the 

 feeding area and the food supply of the corn plant. 



Corn roots or, in fact, the roots of any plants, are sure to 

 grow in the portion of the soil that furnishes the best con- 

 ditions for their growth. In wet years, when the soil is 

 saturated with moisture, there is likely to be a scarcity of 

 air in the soil ; hence the roots of plants will grow quite near 

 to the surface. In dry years, when there is a scarcity of 

 moisture, especially in the surface, the roots will grow deeper 

 in search of moisture. From these facts it is evident that 

 it is safe to cultivate more deeply in dry years than in wet 

 ones. The depth to which the field has been plowed also 

 influences .the depth at which roots will grow most abun- 

 dantly. 



The depth of cultivation should always be regulated by 

 the depth at which the corn roots grow and by the necessity 

 for deep cultivation, such as weeds or a heavy, wet condition 

 of the soil. If deep cultivation must be practiced, it is 

 safer to cultivate deep while the corn plants are small. They 

 then have smaller root systems and are injured less by hav- 

 ing some of the roots broken off. The practice followed by 

 the best corn growers at present is to cultivate deep at the 

 first cultivation, if deep cultivation is necessary at all, and 



