FERTILIZERS 19 



The condition in the soil may be such that the 

 purchase of only one fertilizing element is necessary, 

 and since the source of nitrogen and phosphoric acid 

 and their functions are so many and varied, the 

 question, "What fertilizer to use," and "How to 

 purchase it most economically, "is of vital interest to 

 the farmer and one difficult to solve. 



SOURCE OF FERTILIZERS. 



THE SOURCE OF NITROGEN. 



26. Nitrogen may be obtained from these sources : 

 Air, ammonia, nitrates, and animal matter. In certain 

 forms of animal matter, such as hoofs, horns, coarse 

 bone, leather and wool waste, the nitrogen becomes 

 available too slowly to be of much value. But as 

 green manure, ammonia, nitrates, blood, fine bone, 

 tankage, or blood and bone, fish and finely ground 

 and screened guano, the nitrogen is in good form 

 and soon becomes available. 



27. As these forms require different lengths of 

 time to become available, judgment must be used in 

 their application. Nitrate of soda and sulphate of 

 ammonia dissolve almost immediately in water, so 

 the full amount of a year's supply should not be 

 applied at once, as some will be sure to be lost in 

 waste water. Blood and bone, as a source of nitro- 

 gen and phosphoric acid, would be a better combi- 

 nation than nitrate and bone. Blood and fish re- 

 quire more time to become available than nitrates, 

 and bone, a longer time than blood. (43) 



