110 FIRST PRINCIPLES OF AGRICULTURE. 



Special Formulas. Frequently a large number of 

 different formulas or brands are placed upon the market 

 by the same manufacturers. The claimed purpose in 

 the multiplication of brands is to meet the various de- 

 mands of the consumer, as well as to furnish special 

 preparations which shall provide a large proportion of 

 that constituent which is believed to be of special ser- 

 vice to the particular crop. 



For instance, special potato manures contain a much 

 larger proportion of potash than those intended for gen- 

 eral purposes. Formula No. 1 may be regarded as a 

 special potato manure, while No. 2 may be regarded as 

 a general formula. It must be remembered that the 

 amount of plant-food applied frequently exercises a 

 greater influence than mere proportion of the elements 

 contained in it. The multiplication of brands is seldom 

 of advantage to the consumer. 



The Use of Fertilizers. To use fertilizers to the 

 greatest advantage it is requisite that a great many 

 points should be carefully studied. The character of the 

 manure itself; the soil and previous treatment, both in 

 reference to manuring and cropping ; the climate ; the 

 character of the crop to be grown, and the object of 

 its growth, are, perhaps, the chief factors to be taken 

 into consideration. 



It has already been pointed out that the manurial 

 constituents exist in various degrees of availability, from 

 complete solubility in water to insolubility except in 

 strong acids; the character of both the soluble and the 

 insoluble determines its usefulness to the plant. A 

 correct knowledge of the action of these is, therefore, 



