CHAPTER VI 

 LEGUMINOUS CEOPS 



Nitrogen is no more essential to the growth of corn than 

 certain other elements but it is the one required in the largest 

 amount and is the most easily lost from the soil. Throughout 

 the Corn Belt it is more often the lack of nitrogen than of 

 any other element which limits crop production. "When this 

 supply of nitrogen is low it must be restored before paying 

 grain crops can be grown on the land. 



The object in growing leguminous crops is to restore 

 economically the nitrogen which has been used up by the 

 preceding grain crops. Many so-called worn out soils are 

 worn out only in the sense that the humus (decaying vege- 

 table matter) in them has been used up by the grain crops 

 and clean culture which they received. "When this nitrogen 

 and humus has been restored by the growing of several legu- 

 minous crops, many farms are made as productive as they 

 were when first broken up. 



Leguminous crops such as clover, soy beans, cowpeas, 

 vetches, alfalfa, sweet clover, etc., have the power of taking 

 pure nitrogen from the air and storing it in the roots through 

 the nitrogen-fixing bacteria in the root nodules. At the same 

 time it must be remembered that ' all the nitrogen in the 

 legumes is not stored in the roots but that a considerable part 

 is distributed through the stem and leaves. If, then, hay is 

 removed, all the nitrogen in the stems and leaves is also 

 removed. By removing all the soy bean or cowpea hay it is 

 believed that nitrogen is actually taken from the soil rather 

 than added. It naturally follows that if the nitrogen con- 



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