THE PRINCIPLES OF INTERCULTVEE 205 



140. Jethro Tull said, " Tillage is manure," and this 

 axiom has been more or less accepted and inculcated into 

 our theories regarding the interculture of hoed crops. In 

 the case of small grain crops, which are sown thickly 

 enough to fully occupy the land, benefit has rarely been 

 derived from interculture. With crops which are planted 

 wide apart and which never fully occupy the intervening 

 ground, it has been found profitable to give sufficient 

 interculture to prevent the growth of weeds. 



How much more interculture may benefit the crop than 

 by keeping down weeds is a debated question. Various 

 reasons have been advanced to account for the benefits 

 of interculture and these may be summarized as follows : 



To destroy weeds. 



To conserve moisture. 



To reduce run-off of rainfall by keeping the surface 

 loose and porous. 



To aerate the soil. 



To increase availability of plant food. 



The relative importance of each of the above functions 

 of interculture will vary according to locality and season. 

 Interculture to aerate the soil and to free fertility may be 

 important on certain heavy clay soils in a humid region, 

 but negUgible on more porous soils or in a dry region. 

 Where tojrential rains occur during the growing season, 

 it is important to have the surface in a porous, granular 

 condition. 



In general, however, the conservation of moisture and 

 the destruction of weeds are properly advanced as the 

 principal objects of interculture. Of all objects, the de- 

 struction of weeds appears to be paramount. This con- 

 clusion is arrived at as the result of numerous experiments, 

 which have shown that keeping down weeds by shaving 



