NITROGENOUS MANURES 



150. Sources of Nitrogenous Manures. — The 



materials used for enriching soils with nitrogen, to 

 promote crop growth, may be divided into three 

 classes: (1) organic nitrogenous manures, (2) nitrates, 

 and (3) ammonium salts. Each of these classes has a 

 different value as plant food. In fact there are 

 marked differences in fertilizer value between mate- 

 rials belonging to the same class. The nitrogenous 

 organic materials used for fertilizing purposes are : 

 dried blood, tankage, meat scraps and flesh meal, fish 

 offal, cottonseed meal, and leguminous crops as clover 

 and peas. The nitrogen in these substances is princi- 

 pally in the form of protein. When peat and muck 

 are properly used they may also be classed among the 

 nitrogenous manures. 



151. Dried Blood. — This is obtained by drying the 

 blood and debris from slaughter-houses. Frequently 

 small amounts of salt and slaked lime are mixed with 

 the blood. It is richest in nitrogen of anv of the 



O J 



organic manures. When thoroughly dry it may con- 

 tain 14 per cent, of nitrogen. As usually sold, it con- 

 tains from 10 to 20 per cent, of water, and has a 

 nitrogen content of from 9 to 13. Dried blood 

 contains only small amounts of other fertilizer ele- 

 ments. It is strictly a nitrogenous fertilizer, readily 

 yielding to the action of micro-organisms and to 



