Nitrogenous Fertilizers 43 



decay, and ground leather may remain for years in the 

 soil in an unchanged condition. 



Wool and hair waste are also products which exist in 

 considerable quantities, and while variable in composi- 

 tion, are frequently rich in nitrogen, but they are classed 

 with leather because of their slow activity. Their me- 

 chanical form, coarse and bulky, makes it impossible 

 to use them to advantage in the manufacture of fertilizers 

 without previous treatment. The use of these materials, 

 untreated, can only be regarded as desirable when they 

 may be obtained at a very low cost. When dissolved 

 with acid, or treated in such a way as to render them 

 more immediately available, they may be used to ad- 

 vantage, though the cost of such treatment is usually 

 so great as to make it impossible to thus improve their 

 form and still be able to compete commercially with 

 the other nitrogenous products. 



VEGETABLE NITROGENOUS PRODUCTS 



Cotton-seed meal is one of the best organic nitrogenous 

 fertilizing materials derived from vegetable life. When 

 oil is extracted from cotton-seed, the residue is ground 

 fine and sold as a food for cattle and as a fertilizer. Be- 

 cause it is highly valued as a food for cattle, it has been 

 standardized to contain 38 to 42 per cent protein, equiva- 

 lent to 6 to 7 per cent nitrogen. It contains besides the 

 nitrogen often as much as 3 per cent of phosphoric and 

 2 per cent of potash. When mixed with hulls the per- 

 centages of the elements of plant-food are lower. Tests 

 made show that it ranks with blood in the availability 

 of its nitrogen. Its use as a fertilizer is confined largely 

 to the southern states, where cotton is a staple crop, and 



