78 



TILLAGE FOR CORN 



below the surface. These represent the extremes in depth of surface 

 roots, and cultivation should be regulated accordingly. Cultivation 

 deep enough to destroy roots has always decreased yield when com- 

 pared with more shallow tillage. 



Frequency of Cultivation. Frequency of cultivation depends 

 largely on the weeds to be killed. Rarely have experiments shown a 



FIG. 29. Drawing showing the distribution of corn roots in the soil. 



profit for more than four cultivations, or for continued cultivation 

 after corn was in ear, if free from weeds. At the Illinois Station, 

 "ordinary " cultivation (about four times) was compared with fre- 

 quent cultivation. Plats were also cultivated the same number of 

 times, both deep and shallow. 4 Results were as follows : 



Results of Different Methods of Cultivation 



Average yield 



Kind of cultivation for five years 



Bushels per acre 



Frequent (4 plats) 68.6 



Ordinary (4 plats) 68.5 



Shallow (4 plats) 71.5 



Deep (4 plats) 65.6 



" Illinois Agricultural Experiment Station Bulletin 31, 356. 



