MANURES. 29 



Nitrate of sodium is especially suited for clay land. It is 

 quicker in its action than any other nitrogenous manure, 

 and is therefore the best manure to employ when a late 

 dressing has to be given. 



Soot, Dried Blood, and Woollen Refuse are all purely 

 nitrogenous manures. Soot owes its value to the presence 

 of a small and variable quantity of ammonium salts. 

 Dried blood is an excellent manure, containing 10 to 13 

 per cent, of nitrogen. Shoddy, and other forms of wool 

 and hair are very variable in composition, owing to 

 admixture of dirt, grease, and other foreign matter ; the 

 nitrogen they contain will range from about 5 to 10 per 

 cent. 



The nitrogen of blood, wool, and hair, is not in a form 

 suitable as plant food. Blood readily decomposes in the 

 soil, yielding ammonia and nitric acid. Wool and hair 

 decompose much more slowly, and their effect is spread 

 over many years. 



Soot is generally employed as a top dressing for spring 

 corn. Dried blood is an excellent manure for wheat. 

 Wool and hair are chiefly used for hops. 



Bones. — These are largely employed as manure; the 

 fat is usually first extracted by steaming. Commercial 

 bones contain about 3.6 per cent, of nitrogen, and 23 per 

 cent, of phosphoric acid, existing as phosphate of calcium. 

 Bones that have been boiled to extract the gelatin contain 

 much less nitrogen, but a larger proportion of phosphates. 



Bones decompose but slowly in the soil, especially on 

 heavy land ; their effect is thus spread over several years. 

 The finer the bones have been ground the more immediate 



