294 



THE PRINCIPLES OF SOIL MANAGEMENT 



in absorptive power must be considered, not only to 

 secure the maximum effect upon the crop manured, but 

 also to get the greatest residual effect of the manure 

 upon succeeding crops. 



Fig. 100. Deep and shallow cultivation for corn. On the right-hand side of 

 the picture the deep cultivator shovels are destroying the upper roots. On the 

 left-hand side the shallow cultivation does not reach the roots. 



152. Cereal crops. These plants possess the power of 

 utilizing the potassium and phosphorus of the soil to 

 a considerable degree, but generally require fertili- 

 zation with nitrogen salts. Most of the cereals, like wheat, 

 rye, oats and barley, take up most of their nitrogen 

 early in the season, before the nitrification processes 

 have been sufficiently operative to furnish a large supply 



