CHAPTER IX 

 THE ROTATION OF CROPS 



THE two essential reasons for a rotation 

 of crops are: (i) The possibility of 

 obtaining for the soil a supply of nitrogen 

 from the air by introducing a legume at 

 regular intervals, and (2) the prevention of 

 injury to the crops from fungous diseases, 

 insect enemies, weeds or other causes. Other 

 reasons are often advanced, some of which 

 are entirely erroneous, while others are of 

 quite secondary importance. 



The rotation should be carefully studied 

 with reference to the farm scheme as pre- 

 viously outlined. Reasons for modifying 

 the rotations are: (i) To change the kind 

 or proportion of crops grown, (2) to change 

 the amount of labor required, or (3) to in- 

 crease the crop-producing power of the soil. 



During 25 years the four crops of maize, 



oats, wheat, timothy and clover hay have 



been taken in rotation from the four tiers 



of plats at the Pennsylvania State College, 



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