COMMERCIAL FERTILIZERS jo'' 



Sources of nitrogen, 



'' phosphoric acid, 

 " potash, 

 " lime. 



SOURCES OF NITROGEN 



Nitrogen is the most expensive of plant foods to 

 buy, therefore special attention should be given to 

 producing it on the farm by means of barn manures 

 and -legumes plowed under. 



The principal commercial sources of nitrogen are : 

 Nitrate of soda, sulphate of ammonia, dried blood, 

 tankage, dry ground fish, cotton-seed meal. 



Nitrate of Soda or Chile saltpetre containing 15.5 

 per cent, of nitrogen, is found in large deposits in 

 the rainless regions of western South America. In 

 the crude state as it comes from the mine it con- 

 tains common salt and earthy matter as impurities. 

 To remove these impurities the crude nitrate is put 

 into tanks of warm water. The nitrate dissolves 

 and the salt and earthy matter settle to the bottom 

 of the tank. The water with the nitrate in solution 

 is then drawn off into other tanks from which the 

 water is evaporated, leaving the nitrate, a coarse, 

 dirty looking salt which is packed in three-hundred- 

 pound bags and shipped. 



Plants that take their nitrogen from the soil take 

 it in the form of nitrate. Hence nitrate of soda, 

 which is very soluble in water, is immediately avail- 

 able to plants and is one of the most directly useful 

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