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Reading-Course for Farmers. 



Shall we mix our ozvn fertilisers f 



In preparing a complete fertilizer, the maker mixes some of the 

 above materials in such a way that the resulting mixture may contain 

 the nitrogen, phosphoric acid and potash in the desired proportion. 



For example : suppose it is desired to have a mixed fertilizer to 

 contain 2 per cent, nitrogen, 8 per cent, phosphoric acid and 4 per cent, 

 potash, and the amount desired is one ton of 2,000 pounds. The ton 

 will therefore have 40 pounds nitrogen, 160 pounds phosphoric acid ana 

 80 pounds potash, because 



2 per cent, of 2,000 pounds = 40 pounds 

 8 per cent, of 2,000 pounds = 160 pounds 

 4 per cent, of 2,000 pounds = 80 pounds. 



The next step is to learn how many pounds of some substance con- 

 taining nitrogen, will furnish the 40 pounds of nitrogen. If dried blood 



Nitrogen. Potash. Phos. Acid. No fertilizer. 

 Fig. 343 — Potatoes harvested from four of the experimental plats of Mr. M. C. Hatch- 



is to furnish the nitrogen, and the dried blood should contain 12 per 

 cent, of nitrogen (that is, each 100 pounds of dried blood has 12 pounds 

 of nitrogen), then by calculation it is seen that 333 pounds are needed. 

 This is best shown by the old " rule of three," or the rule of proportion : 

 One hundred pounds dried blood equal 12 pounds nitrogen. How 

 many pounds dried blood equal 40 pounds nitrogen? 



40 X 100 



100 : 12 : : X : 40 = 333 



12 



