374 CROP GROWING AND CROP FEEDING 



POUNDS PER ACRE, TOPS AND ROOTS. 



To furnish the same amount of nitrogen per acre there would be required 

 of nitrate of soda: 



Pounds. 



In case of flat pea 1495.7 



In case of Canada pea 716.3 



In case of spring vetch 795.7 



In case of sand vetch 495.9 



In case of red clover 898.2 



In case of white clover 1086.3 



In case of alsike clover 749.0 



In case of crimson clover 676.8 



It must be remembered, however, that when these crops are cut for hay 

 a considerable proportion of the nitrogen is removed in the tops, but there 

 will still remain, in the organic matter of the roots and stubble, far more 

 than is usually applied in a ton of high grade fertilizer. The following 

 table from the Virginia Station gives the results from the application of 

 different forms of fertilizers on the wheat crop. The amounts applied w^re 

 sufficient to supply all the phosphoric acid and one-half the potash and nitro- 

 gen removed by a crop of wheat of 25 bushels per acre: 



Phosphoric acid was evidently the controlling factor. 



