SOURCES AND COMPOSITION OF FERTILIZERS 297 



contains 6 to 8 per cent, nitrogen, about 1.5 per cent, potash, and 

 2.5 per cent, phosphoric acid. 



Cotton seed have approximately one-half the fertilizing value of 

 the meal. They contain approximately 3 per cent, nitrogen and 

 1.2 per cent, each of phosphoric acid and potash. 



Linseed meal contains less nitrogen than cottonseed meal. The 

 demand for this product for feeding purposes makes it an 

 expensive source of nitrogen in fertilizers. 



Castor pomace is not useful as a cattle food. It is about as 

 rich as linseed meal, and is a good fertilizer. It contains 5 to 6 

 per cent, nitrogen and i.o to 1.5 per cent, each of phosphoric acid 

 and potash. 



Bat guano is the excrement of bats, found to a limited extent 

 in caves in Texas, Mexico, and Porto Rico. It is liable to 

 spontaneous combustion, the residue being known as bat guano 

 ash, which is not easily distinguished from bat guano. Bat guano 

 is variable in composition, ranging from a compound rich in nitro- 

 gen to one rich in phosphoric acid. It contains from 2 to 12 per 

 cent, nitrogen and from i to 8 per cent, phosphoric acid. 



Hoof and horn meal is a by-product from the making of var- 

 ious articles from hoofs and horns. It contains about 14 per 

 cent, nitrogen. 



Slowly Available Nitrogenous Fertilizers. These materials give 

 up their nitrogen very slowly, so that they often have little or no 

 effect upon the crop to which they are applied. In many States 

 the use of these materials in mixed fertilizers is prohibited. 



Leather scraps is a waste product from various factories, and 

 is sold as raw leather, steamed leather, and roasted leather. It 

 contains about 7 to 8 per cent, nitrogen. 



Hair is a product from slaughter houses, containing 9 to 14 per 

 cent, nitrogen. 



Peat and muck may contain as much as 2 per cent, nitrogen. 



Wool waste is a by-product from woolen factories. 



Availability of Nitrogenous Fertilizers. The nitrogen of nitrate 

 of soda and ammonium sulphate may be taken up directly by 

 plants, but the value of the other nitrogenous materials depends 

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