194 SOILS AND PLANT LIFE 



how near the roots are to the surface. After the cultivator 

 has gone through the field once, we should scrape away 

 the earth in two or three places to see if any of the roots 

 have been cut or broken off. 



It is in the upper three or four inches of soil that avail- 

 able plant food is most abundant, and this is the feeding 

 ground of many important roots of the corn plant. It is 

 self-evident that they should not be destroyed. It is 

 safe to say that a great deal of the damage that has been 

 sustained by farmers of the Corn Belt in the past as the 

 result of drouths was avoidable in the sense that it was 

 the direct effect of the severing of feeding roots at a time 

 when the plants were unable to withstand this treatment 

 without serious injury. 



132. Frequency of Cultivation. — The number of times 

 that corn should be cultivated is determined by certain 

 conditions which are highly variable. Since the purposes 

 of cultivation are mainly to destroy weeds and to conserve 

 moisture, we may say that the frequency of cultivation 

 depends upon the weediness of the field and upon the 

 number of beating rains which it may receive. It is a 

 mistake either to allow weeds to become established in the 

 field or to allow a crust, from which moisture can escape, 

 to form and remain on the surface; and on the other 

 hand it is inadvisable to cultivate soil when it is already 

 free from weeds and its surface finely pulverized. 



It should be noted in this connection that mere size 

 constitutes no good reason for discontinuing the cultiva- 

 tion of com, or, as we say, " laying it by." It is true 

 that when the plants become large enough to shade the 

 ground effectually, the growth of weeds is checked to some 

 extent, but it is also true that much more moisture is 

 needed at this stage than at any other and that its con- 



