SOIL MANAGEMENT 23 



of commercial fertilizers purchase these basic materials and mix 

 them together in proportions to give the percentages of nitrogen, 

 phosphoric acid and potash required for their particular brands. 

 Some of these basic materials, such as nitrate of soda, or acid 

 phosphate contain only one of the essential elements while others 

 like bone, or tankage, contain two of .the essential elements. The 

 materials used in the manufacture of fertilizers are known as 

 carriers. 



Nitrogen carriers. — The principal carriers of nitrogen are 

 dried blood, meat, hoof and horn meal, tankage, dried fish, 

 leather meal, nitrate of soda, and sulphate of ammonia. 



Dried blood is the blood from slaughterhouses that has been 

 dried rapidly and ground into a fine powder. It contains from 

 six to fourteen per cent of nitrogen, the exact amount depending 

 upon the method of preparation. 



Meat, Jioof mid horn meal are dried animal materials from 

 slaughterhouses and rendering establishments, ground to fine 

 meal. These materials contain from ten to fourteen per cent of 

 nitrogen, that in the meat meal being much more readily avail- 

 able than that in the hoof and horn meal. 



Tankage consists of the dried waste materials from slaughter- 

 houses and is quite variable in composition. It derives its value 

 both from the phosphoric acid as well as from the nitrogen which 

 it contains. The nitrogen content varies from four to nine per 

 cent and the phosphoric acid from three to twelve per cent. 



Dried fish is derived largely from the menhaden fisheries of 

 the Atlantic coast and from canning factories. The fish are 

 steamed and pressed to remove the oil after which the remains 

 are dried and ground. This product contains from eight to 

 twelve per cent of nitrogen and three to five per cent of 

 phosphoric acid. 



Leather meal is made from small scraps of leather that have 

 been ground into a fine powder. Because of its low availability 

 it is not a desirable source, of nitrogen, and in some states manu- 

 facturers who use leather or hair waste must make a statement 

 of that fact in giving the analysis of the fertilizer. 



Nitrate of soda is a substance closely resembling coarse table 

 salt, and since it comes from Chili it is sometimes called Chili 

 saltpeter. It contains fifteen to sixteen per cent of nitrogen and 

 is quickly and completely soluble in water, consequently its 

 nitrogen is readily available to plants. 



Stdphate of ammonia is a by-product in the manufacture of 

 gas, animal charcoal and coke. It also resembles common salt 



