. (COMMERCIAL FKRTILIZEBfi 133 



(II \ITKi: \ \\\— Commercial Fertili/ 



127. Definition of Commercial Fertilizers. — Artificial 

 manures, or commercial fertilizers, are such sompounds 



manufactured expressly for use "ii soils. Phey 

 may be divided into' three classes: L NTitrogenous 

 fertilisers, including such compounds as ire used to 

 supply nitrogen. 2, P fertilisers, compounds 



supplying potash. 3. Phosphates, compounds sup- 

 plying phosphorus. 



128. Nitrogenous Fertilizers. — Nitrogen compound 

 arc the most expensive of all fertilizers, and as nitrogen 



• n lacking in soils these fertilizers are of th* 

 importance. The nitrogen of fertilizers is supplied by 

 a number of different compounds, and the more impor- 

 tant of these will now be briefly descril>ed: 



1 Bodmin nitrate, often called Chile saltpetre, is a 

 Compound °f nitrogen with sodium and oxygen, con- 

 taining about 16 per cent of nitrogen. It is a salt and 

 hies in appearance ordinary table salt. It occurs 

 naturallv in great deposits, the best known of which 

 are in Chile j hence its name. It i< wry impure when 

 mined, ami before it can 1k» used as a fertilizer must 

 be purified. The crude salt i- dissolved in water which 

 i» afterwards evaporated, when the purified compounds 



t in the form of small crystal-. Nitrate of soda 

 is easily soluble in water, and as plants take up their 

 nitrogen in the form <>f nitrafc Ly for the 



use of plants as soon as dissolved in the soil WS 



