Nitrogenous Fertilizers 53 



Potassium nitrate. It has already been stated that 

 potassium nitrate salts exist in Egypt and India. They 

 are also found in Cape Colony, South Africa. The impure 

 salts on the market, commonly called niter or saltpeter, 

 contain 14 per cent of nitrogen and 44 per cent of potash. 

 Because this material is used for manufacturing purposes, 

 especially gunpowder, little is sold for fertilizer even 

 though it is especially concentrated considering its con- 

 tent of both nitrogen and potash. 



Ammonium nitrate is a compound now being manufac- 

 tured in Norway which is superior to the other nitrogenous 

 products in that it is highly concentrated and leaves no 

 injurious residue in the soil. Chemically pure, it contains 

 35 per cent of nitrogen, one-half in the ammonia form 

 and one-half in the nitrate form. The commercial prod- 

 uct, yet limited in quantity, is sold on the dry basis 

 99.8 per cent pure. At the present time, the cost of 

 nitrogen contained is too high to warrant the use of this 

 material as a fertilizer. 



THE RELATIVE AVAILABILITY OF THE DIFFERENT FORMS 



OF NITROGEN. See Fig. 2, Plate 2. 



From this discussion of the kind and source of 

 nitrogenous fertilizer supplies, it is shown that the form 

 of the nitrogen is an important factor in determining the 

 rate at which the plants may obtain it. In the case of 

 nitrate, the form is such as to enable the plants to take 

 it up immediately. It is, therefore, theoretically the 

 best, because as soon as it comes in contact with the roots, 

 it is absorbed by them; there is no appreciable time re- 

 quired to enable the element to get into a condition 

 capable of ready absorption by the plant. Furthermore, 



