NITROGENOUS MANURES 137 



equivalent of sodium nitrate. It is, however, a valua- 

 ble form of nitrogen. The statements made regarding 

 the use of sodium nitrate apply equally well to the use 

 of ammonium sulphate. Ammonium chloride and 

 ammonium carbonate are not suitable for fertilizers on 

 account of their destructive action upon vegetation. 



162. Nitrogen and Ammonia Equivalent of Fer- 

 tilizers. — Nitrogenous fertilizers are sometimes 

 represented as containing a certain amount of ammo- 

 nia instead of nitrogen ; this is so that a higher per- 

 centage may be made to appear. Fourteen-seven- 

 teenths of ammonia is nitrogen, and if a fertilizer is 

 said to contain 2.25 per cent, ammonia, it is equiva- 

 lent to 1.85 per cent, of nitrogen. 



163. Purchasing Nitrogenous Manures. — In pur- 

 chasing 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 im- 

 poverished soil, sodium nitrate is desirable. Under 

 other conditions tankage, cottonseed cake, or some * 

 other form of nitrogen may be made to answer the 

 purpose. There is annually expended in purchasing 

 nitrogenous fertilizers a large amount of monev which 

 could be expended more economically, if the science 

 of fertilizing were given a more careful study. 



