THE ROTATION OF FARM CROPS 61 



as good a money crop as oats and has a big advantage over 

 oats since it is building up the land instead of running it 

 down. 



ROTATION IMPROVES THE PHYSICAL CONDITION OF THE SOIL 

 AND INCREASES ITS FERTILITY 



The roots of the different crops are of great aid in pul- 

 verizing (and fining) the soil. When deep rooted legumes are 

 grown in rotation they utilize and bring to the surface plant 

 food which lies beyond the reach of the short rooted cereals. 

 When the roots of these legumes decay this nitrogenous plant 

 food is left in the surface soil to be used by the succeeding 

 grain crops. 



While there is a slight improvement in the physical con- 

 dition of the soil when different grain crops alone are rotated, 

 the greatest benefits of rotations are derived from the legumes 

 included. For this reason at least one leguminous crop 

 should be included in every crop rotation. 



The increase in the fertility of the soil as a result of crop 

 rotations is due entirely to the additional nitrogen stored in 

 the soil by the legume. If the leguminous crop is taken off 

 the land each time it is grown it is doubtful if any nitrogen 

 is added. When soy beans and cowpeas are grown and the 

 hay is taken off and no manure is returned it is believed that 

 nitrogen is actually taken from the soil rather than added. 

 If soy beans and cowpeas are grown for the seed, the straw 

 should be returned to the land after the seed has been 

 threshed out. Since a good supply of nitrogen is essential 

 for the profitable growing of grain crops, and the only cheap 

 way to get this nitrogen is by growing legumes, every effort 

 should be made to leave as much of the crop on the land 

 as is possible. 



We wish to say, right here, that crop rotation alone will 



