NITROGENOUS MANURES 129 



ing. Its use for fertilizing horticultural crops has be- 

 come equally as extensive as for general farm crops. 

 Excessive amounts may produce injurious results. 

 Sodium nitrate stimulates a rank growth of dark 

 green foliage, and retards the maturity of plants, "but 

 when properly used is one of the most valuable of 

 the nitrogenous "fertilizers. 



162. Ammonium Salts. Ammonium sulphate is 

 obtained as a by-product in the manufacture of illumi- 

 nating gas and is extensively sold as a fertilizer. It 

 usually contains about 20 per cent, of nitrogen, equiv- 

 alent to 95 per cent, of ammonium sulphate, the re- 

 maining 5 per cent, being moisture and impurities. 

 Ammonium sulphate is not generally considered the 

 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. 



163. Nitrogen and Ammonia Equivalent of Fer- 

 tilizers. Nitrogenous fertilizers are sometimes 

 represented as containing a certain amount of ammo- 

 nia instead of nitrogen. Fourteen-seventeenths of 

 ammonia is nitrogen, and if a fertilizer contains 2.25 

 per cent, ammonia, it is equivalent to 1.85 per cent, 

 of nitrogen. To convert NH results to an N basis 

 multiply by 0.823. 



164. Purchasing Nitrogenous Manures. In pur- 

 chasing nitrogenous manure, the special purpose for 

 which it is to be used should always be considered. 



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