CHAPTER V. 



HIGH GRADE NITROGENOUS FERTILIZER MATERIALS. 



Nitrogen is the most important element to consider in the study 

 of fertihzers. It is the most expensive and most fugitive of the 

 essential elements. Nitrogen usually costs about three times as 

 much as phosphoric acid or potash. To be in a form available 

 as plant food it must be as nitrates which are readily soluble in 

 water. The air is made up of nitrogen, carbon and oxygen and 

 although plants utilize the carbon and oxygen most of them do 

 not seem to be able to use the nitrogen. There is one class of 

 plants, the legumes (peas, beans, peanuts, alfalfa, clover, etc.) 

 of which we have spoken, that can utilize this elementary nitro- 

 gen but most of our other plants do not possess this power. 

 The organic matter, which is made up of animal and vegetable 

 matter, serves as a source of nitrogen, but plants cannot use it 

 in this form. It is understood then that there is plenty of un- 

 usuable nitrogen in the air and in soils rich in organic matter, but 

 it has no direct plant food value in these forms until it is prepared 

 by electrical means, oxidized and acted upon by certain bacteria. 



Forms of Nitrogen. — Nitrogen exists in different forms in the 

 many substances containing it. Not including the nitrogen in the 

 air we may classify these forms into four groups, namely : 



1. Organic nitrogen, which is found in vegetable and animal 



substances, generally as protein. 



2. Ammonia nitrogen, which is found in ammonium sulphate. 



3. Nitrate nitrogen, which is found in nitrate of soda (Chile 



saltpeter) and nitrate of potash. 



4. Cyanamid nitrogen, which is taken from the air by electrical 



means and combined with calcium, carbon, etc. 



Of these four forms all are soluble in water except organic 

 nitrogen. The organic form is included in many substances, 

 both animal and vegetable, while the remaining forms are found 

 principally in a few products. 



The Meaning of the Form of Nitrogen. — The fertilizer mater- 

 ials furnishing nitrogen contain this element in different forms. 



