Manures in General 



a time when an increase of manure would not give 

 a similar increase of production, and the practical 

 limit is when the addition of manure ceases to give 

 good extra value in the produce. In reality one 

 would never push the practice as far as the point 

 where the production did not do more than pay for 

 the manures, though in theory it can sometimes be 

 justified — say by the production of the most nourish- 

 ment on a given site, thus making a larger head of 

 stock possible. 



It is often written and more often said that 

 " basic slag or superphosphate " (of good quality, be 

 it understood) " do not answer." Such a statement 

 proves that the manure has not been given a sufficient 

 trial, and, moreover, that the experimenter is not 

 familiar with the use of chemical manures. One 

 thing is certain. The soil lacks phosphoric acid : 

 the exceptions to this rule are too rare to make one 

 believe anything to the contrary. If basic slag 

 and superphosphates do not respond, it means that 

 they have not been given their proper complement — 

 they cannot respond. They must be given in 

 combination with potash or nitrogen, sometimes 

 with both, and then they will answer. The Law of 

 the Minimum must be satisfied. 



The Selection of Manures. 



It only remains to decide what manures must be 

 used to bring their importation to the utmost limit 

 of economic possibilities. There are in commerce 

 such a quantity and variety of artificial and chemical 

 manures, that there is some difficulty in choosing. 

 They may be divided into — 



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