Nitrogenous Fertilizers 57 



from dried ground fish and hoof meal would be 650 pounds, 

 from bone and tankage 600 pounds, and from leather, 

 ground horn and wool waste, from 20 to 300 pounds. 

 The foregoing discussion shows very clearly that 

 organic, ammonia and nitrate nitrogen have a very 

 unequal value as sources of nitrogen. Nitrate nitrogen, 

 the most valuable of all three, is seldom if ever entirely 

 used by the crop. Conditions determine in a large 

 degree the proportion of the nitrate nitrogen secured by 

 the crop, because a smaller or larger amount escapes 

 beyond the reach of the plant by leaching or into the air 

 by denitrification. The amount of nitrogen returned by 

 the crop in the harvest is, therefore, a direct means of 

 determining the relative availability of nitrogen from the 

 three different forms. Investigations conducted by Paul 

 Wagner, Darmstadt, Germany, and the author, Edward. 

 B. Voorhees, of the New Jersey Experiment Station, agree 

 very closely. Conclusions from these works show that 

 there was returned in the harvest 62 parts of nitrate 

 nitrogen for every hundred parts applied; 44 parts of 

 ammonia nitrogen for every hundred parts applied and 

 40 parts of organic nitrogen for every hundred parts ap- 

 plied as dried blood. Hence, with the returns from 

 nitrate, the highest recovery regarded as 100, the relative 

 availability of the nitrogen as ammonia would be 69.7 

 and of nitrogen as dried blood as 64.4. These figures 

 possess great practical significance to the farmer buying 

 and using the nitrogen now offered on the market in 

 fertilizers. 



Conditions which modify availability. 



The foregoing discussion and figures alone are, however, 

 not a sufficient guide as to the kinds to buy under all 



