Commercial Fertilizers. 149 



Sulphate of ammonia. This material is from the gas works 

 and is obtained as a by-product in the manufacture of illumin- 

 ating gas. It is the most concentrated nitrogenous material in 

 the market and contains from 20 to 23 per cent of nitrogen, 

 equivalent to about 25 per cent of ammonia. It is very soluble 

 in water, does not readily leach out of the soil, and undergoes 

 nitrification very quickly, being converted into nitrates. How- 

 ever, some plants may take a part of their nitrogen supply di- 

 rectly as ammonium salts, when so applied. The sulphate gives 

 good results on soils containing plenty of lime. It should not 

 be used on soils deficient in lime, because of its tendency to leave 

 the soil acid. 



Nitrate of soda. This fertilizer is known under the name of 

 "Chili salt petre" and occurs in deposits of considerable extent 

 in Chili. When crude it is called " caliche" and contains vary- 

 ing amounts of impurities, chiefly common salt. It is freed from 

 these impurities by solution and crystalization and when put 

 upon the market contains from 95 to 97 per cent of nitrate of 

 soda, This final product contains from 15 to 16 per cent of 

 nitrogen. Chili supplies over a million tons of nitrate a year 

 to be used as a fertilizer. This substance contains its nitrogen 

 in the most readily assimilable form, and in the form into which 

 most other nitrogenous bodies must be converted before they are 

 taken up by the plant. It is not fixed by the soil and unless 

 growing crops are at hand to take it up, it will be leached out by 

 rains. Consequently it should be applied as a top dressing and 

 in not too heavy applications. It is best applied early in the 

 spring soon after the plants have started their growth and should 

 be. mixed with at least double its weight of soil before being ap- 

 plied, as otherwise harm to the plants may result. It should not 

 be applied to grain crops late in the season. 



Nitrate of potash. This is commonly known as "salt petre" 

 and is one of the most concentrated fertilizing materials we have, 

 since it contains both nitrogen and potash in available forms. 

 It contains about 13 per cent of nitrogen and from 42 to 45 per 



