15 



The above, together with some seed residues, are the 



main sources of organic nitrogenous fet'tllizers that are 



spread over the ground. There are however, some chenical 



fertilizers which are very important sources of available 



nitrogen. They may be emomerated as follows. 



Sodium nitrate(:'Q., i: 0^ ) This is commonly known as 



Chilli Saltpeter. It is found in an extensive natural deposit 



in Chili, Peru, and in the United States of Colu^nbia.. "*hen 



pure, this salt contains 16.49^ of available nitrogen but the 



ordinary commercial article contains on an average 16^ and 



cost anywhere from "j/SCOO to .'|)'.60.00 a ton, making the nitrogen 



itself worth about. 15 or 18 cents a pound. It is soluble, and 



does not have to under go the ordinary nitrifying processes. 



It is therefore one of the most, if not the most active 



.,r 

 nitrogenous fertilizer being as t4 is directly available as 



plant food. 



-i^sunoniura Sulphate (K H )S 



3 »- 4 



This salt is obtained as a bi-product in the manufacture 

 of illuminating gas and is extensivelt sold as a fertilizer. 



Phosphate Fertilizers. 

 The chief sources of phosphate fertilizers are,- 



(1) Phosphate rock- This is found in many parts of 

 the United States, particularly in South Carolina, Florida, 

 Virginia and Tennessee. They usually contain from 17 to 30^ 

 of phosphoric acid. 



(2) Phosphate slag- In refining of iron ores by 

 the Bessemer process, the phosphorus in the iron is removed as 

 a basic slag. This is variable in composition and at present 

 but little is formed in this country that is available as 



