COMMERCIAL FERTILIZERS IN HORTICULTURE. 165 



in practice, demands more careful consideration than does the 

 nitrogen supply. 



First. The element is expensive, for it costs nearly three times 

 what the other two do. 



Second. It is subject to greater possibilities of waste than any 

 other commercial element of plant food. 



Third. It may be, and is, derived in part from inferior sources. 



The third and last statement is the one with which we are 

 mainly concerned in today's discussion. 



The nitrogen of fertilizers is found to be combined in three 

 general forms, viz. : in nitric acid or nitrates, in ammonia or 

 ammonium salts, and in vegetable and animal substances, which 

 as a class are called organic ammoniates. The only representative 

 of the first class, which enters into the fertilizer trade is nitrate 

 of soda. In this we have the nitrogen as nitric acid, the form 

 adapted par excellence for the uses of the plant. We have reason 

 to believe that nitrogen enters the plant largely in this combina- 

 tion, and that other forms are to a great extent changed to this 

 before becoming useful. 



Standing next to nitrates in point of value, and perhaps 

 scarcely below, are the' ammonium compounds, sulphate of 

 ammonia being the only one entering into the list of fertilizer 

 supplies. This is the most concentrated nitrogenous fertilizer we 

 have, and even though its nitrogen may suffer conversion into 

 nitric acid wholly or in part before being utilized, it takes a place 

 second to nitrate of soda, if at all, only upon theoretical grounds, 

 for in practice it is found to act with entire promptness and 

 efficiency in promoting growth. 



When now we come to a consideration of the organic 

 ammoniates actually found in the markets, it is not possible to 

 speak of them all in terms of approval. A fairly complete list of 

 these ammoniates are the following : Dried blood, dried meat, 

 tankage (which may be varied in character and may cover a 

 multitude of sins), ground bone, dried fish, fish scrap, hoof and 

 horn meal, waste hair, waste meal, leather, cotton seed meal, and 

 castor pomace. 



These materials are classified as to agricultural value according 

 to their availability, or the readiness with which the nitrogen is 

 carried over (through processes of fermentation and decay) into 

 compounds which the plant can utilize. Judging from this stand- 

 point those organic ammoniates which should be ranked as 



