MANUFACTURED COMMERCIAL FERTILIZERS 525 



Cotton seed. Cotton-seed meal contains about i per cent 

 each of phosphorus and potassium. Sometimes the whole cotton 

 seed, containing about 3 per cent of nitrogen, is used directly as a 

 fertilizer, but as practically all of the plant food remains in the 

 hulls and cake (after the oil is expressed) , the meal is now largely 

 used, and more profitably, of course, unless the farmer pays more 

 for his nitrogen than he received for the same amount in seed, 

 which is likely to be the case if he buys ready mixed "complete" 

 fertilizer. The annual production of cotton seed in the United 

 States amounts to about 6 million tons. 



Fish scrap. Fish-scrap meal contains about 8 per cent of nitro- 

 gen and 6 per cent of phosphorus. There are various other sources 

 of organic nitrogen, some of which, like hoof meal, furnish avail- 

 able nitrogen, while others, like hair, wool waste, and horn meal, 

 are very slowly nitrified. 



Ammonium sulfate. Commercial ammonium sulfate is usually 

 about 95 per cent pure, containing 20 per cent or more of nitrogen. 

 It is obtained by washing coal gas through dilute sulfuric acid and 

 concentrating the liquid until the ammonium sulfate crystallizes 

 out. About 100,000 tons of ammonium sulfate is the present 

 annual production from the gas plants and coke ovens in the 

 United States, and the production is likely to largely increase, 

 because most of the American coke ovens are still wasting the 

 ammonia produced. 



Sodium nitrate. Sodium nitrate of commercial grade is about 

 95 per cent pure, and contains 15 per cent or more of nitrogen. It 

 is obtained from the extensive nitrate beds of Chile, where it is 

 found in very extensive deposits, thought to have resulted from 

 the decomposition of seaweed in connection with sea salt. The 

 impure material is leached and the nitrate secured by crystalliza- 

 tion. The exportation began about 1830 and has quite steadily 

 increased from 8000 tons in 1840 to about 2 million tons in 1908, 

 the total exportation from 1830 to 1909 amounting to about 40 

 million tons, which is about one sixth of the estimated 1 amount re- 

 maining in the Chilian and Peruvian beds. The export duty 



1 The estimates of ten years ago placed the total supply at 81 million tons, but 

 a so-called official report made in 1909 (American Fertilizer) estimates 246 million 

 tons. 



