ARTIFICIAL MANURES OR FERTILIZERS. 101 



CHAPTER IX. 



Artificial Manures or Fertilizers ; Methods of Buying ; Valuation ; 

 Formulas. 



THE fertilizing materials described in the three preced- 

 ing chapters are the raw materials, and are the main 

 sources of supply of plant-food to manufacturers and to 

 farmers. 



Standard High-Grade Materials. Such materials 

 as nitrate of soda, sulphate of ammonia, dried blood, bone 

 black, and South Carolina rock superphosphates, and the 

 various potash salts, are called standard products. Dif- 

 ferent samples of any of these do not vary widely in 

 their composition, and those of the same kind are prac- 

 tically uniform in their action. For instance, any one ton 

 of nitrate of soda contains practically the same amount 

 of nitrogen as any other ton, and the nitrogen is always 

 in the form of a nitrate. 



They are standard because they can be depended upon, 

 both in respect to composition and form of the essential 

 element. These are important advantages not possessed 

 by the natural manures or fertilizing materials derived 

 from other sources. They are also called " chemical " or 

 "high grade," because they are in most cases chemical 

 compounds, and because they furnish those particular ele- 

 ments in their most concentrated and active forms. 



