NITROGEN, NITRIFICATION, NITROGENOUS MANURES 1 57 



176. Nitrogen and Ammonia Equivalent of Fertilizers. 



Nitrogenous fertilizers are sometimes represented 

 as containing a certain amount of ammonia instead of 

 nitrogen. Fourteen-seventeenths of ammonia is nitro- 

 gen, and if a fertilizer contains 2.25 per cent ammonia, 

 it is equivalent to 1.85 per cent of nitrogen. To convert 

 NH 3 results to an N basis, multiply by 0.823. 



177. Purchasing Nitrogenous Manures. In purchas- 

 ing a nitrogenous manure, the special purpose for which 

 it is to be used should always be considered. Under 

 some conditions, as forcing a crop on an impoverished 

 soil, sodium nitrate is desirable. Under other conditions, 

 tankage, cottonseed cake, or some other form of nitro- 

 gen may be better. There is annually expended in pur- 

 chasing nitrogenous fertilizers a large amount of money 

 which could be expended more economically if the 

 science of fertilizing were given a more careful study, 

 and if a larger share of the nitrogen for crop pur- 

 poses were obtained indirectly from the air through the 

 agency of legumes. The uses of nitrogenous fertilizers 

 for special crops and the testing of soils to determine 

 any deficiency in nitrogen are discussed in Chapters 

 X and XI, which treat of commercial fertilizers and the 

 food requirements of farm crops. 



