-18- 



years acid phosphate was added at the rate of 169 pounds 

 KgO and 129 pounds P2O5 per acre. The results of this 

 experiment ae a whole were considered negative, since fas 

 annual increase in combined yield of all varieties on the 

 treated plots barely paid the cost of the fertilizers and 

 their application. 



These experiments do not prove that pertilization is 

 always made with negative results, but simply show that 

 the fruit grower should test for himself what plant food 

 his soil needs. 



Nit roj^en fer t i l izers. 



Sodiuu a ni t rate^ (Na N03) . 



This salt is the principal source of inorganic 

 nitrogen in commercial fertilizers. The chemically pure 

 salt, nitrate of soda, contains 16.47 per cent 6f nitrogen 

 and the commercial article, called "Chile Saltpeter" con- 

 tains from 15.5 to 16 per cent. Nitrogen in the nitrate 

 form is easily taken up by the plant and for this reason 

 acts quickly in inducing growth. 



Ammonium suljthate (N Hg)^ S (),, 



Sulphate of ammonia is a chemical salt which, 

 when pure, contains 21.8 per cent of nitrogen. In com- 

 mercial forms, however, it usually contains about 20 per 

 cent of nitrogen. Sulphate of ammonia is obtained from 

 the dry distillation of animal bone in the manufacture 

 of bone-black, and also from the distillation of coal in 



