224 Bureau of Farmers' Institutes. 



( h) Commercial fertilizing materials containing phosphoric acid 

 compounds. 



(c) Commercial fertilizing materials containing potash com- 

 pounds. 



(d) Farm-produced fertilizing materials. 



This division is not sharply defined, since one material may 

 contain more than one form of nutriment; however, in most GPges, 

 each kind of material contains some one of the three forms of 

 plant food in much larger proportions than any other form. Ow- 

 ing to the value of farm-produced manures and to the importance 

 of calling special attention to their value, we treat this subject, 

 under a separate head in connection with the forms of materials 

 used in commercial fertilizers. 



(a) Fertilizing Materials Containing Nitrogen Compounds. 



The various materials which are used to furnish nitrogen m 

 commercial fertilizers are derived from three general sources, 

 which we can indicate as follows: 



(1) Mineral nitrogen compounds. 



(2) Vegetable nitrogen compounds. 



(3) Animal nitrogen compounds. 



(1) Commercial Fertilizing Materials Containing Mineral Nitro- 

 gen Compounds. 



The forms of mineral compounds containing nitrogen, most com- 

 monly found in the market, are nitrate of soda and sulphate of 

 ammonia. 



Nitrate of Soda, known also as " Chili saltpeter," is found 

 in large deposits which have been formed in the rainless regions 

 of Chili and Peru. As it is mined, the nitrate of soda is quite' 

 impure, the chief impurity being common salt. Before being 

 sent to market, it is purified, and the form in which farmers pur- 

 chase it generally contains from 95 to 96 per cent, of real nitrate 

 of soda. Stated in another way, 100 pounds of good commercial 

 nitrate of soda contain from 15^ to 16 pounds of nitrogen. 



Sulphate of Ammonia is formed from waste materials pro- 

 duced in the manufacture of illuminating gas. This is the most 

 highly concentrated form of nitrogen commonly found in the 

 market. One hundred pounds of sulphate of ammonia contain 

 about 25 pounds of ammonia, which is equivalent to about 20^- 

 pounds of nitrogen. 



