76 FIELD CROPS 



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

 are 12 to 15 inches high (Figure 17). As 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 supph' of the corn plant. 



Corn roots or, in fact, the i-oots of any plants, arc sure to 

 grow in the portion of th(^ 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 

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

 ture, especiallj^ in the surface, the roots will grow deeper 

 in search of moisture. It is thus 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 wliich roots will grow most abundantlj'. 



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 

 then to cultivate as shallow as is consistent with keeping the 

 soil in good condition and free from weeds. 



93. Frequency of Cultivation. If care is exercised not to 

 disturb the roots of the corn plant, cultivating often enough 

 to keep down weeds and to maintain a good surface mulch 

 to retain moisture is desirable. The soil can usually be 

 kept in good condition bj- cultivating three or four times, 

 but sometimes six or even eight times is more profitable. 



The impression used to be quite general that it was not 

 advisable to cultivate corn after it had tasseled. There 



