122 AGRICULTURE 



Societies issue annually to their members, 

 usually in spring, a statement of the unit 

 values of standard manurial substances. By 

 means of these units, or of others which the 

 farmer can readily work out for himself, it is 

 easy to ascertain whether manures that are 

 offered are worth the money demanded or 

 not. If, for instance, in any one year 

 standard nitrate of soda containing about 

 15 1 per cent, of nitrogen has a unit value of 

 12s., that would mean that the price of a ton 

 should be 9, 6s. Supposing that another 

 sample of nitrate of soda were offered con- 

 taining only 14 per cent, of nitrogen, 

 the corresponding value per ton would be 

 8, 8s. ; but having regard to the fact 

 that the lower the quality the relatively 

 higher is the cost of carriage, it must be 

 said that 8, 8s. is rather too high a 

 price to pay for the lower-quality manure. 

 Certainly if more than this price is demanded 

 as is most likely, for poor manures are 

 seldom cheap it is relatively dearer than 

 the other at 9, 6s. If, on the other hand, 

 it can be purchased much below 8, 8s., then 

 it is relatively the better value. 



If, after considering the various factors 

 that determine one's choice of a nitrogenous 

 manure, the farmer has still a difficulty in 



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