NITROGEN, NITRIFICATION, NITROGENOUS MANURES 147 



Each of these classes has a different value as plant 

 food, and in fact there are marked differences in fertili- 

 zer value between materials 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 sub- 

 stances is principally in the form of protein. When 

 peat and muck are properly used they also may be 

 classed among the nitrogenous manures. The mineral 

 nitrogenous manures are nitrates, as sodium nitrate, and 

 ammonium salts, as ammonium sulphate. 



164. Dried Blood. This is obtained by drying the 

 blood and debris from slaughterhouses. Frequently 

 small amounts of salt and slaked lime are mixed with 

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

 organic manures. When thoroughly dry it may contain 

 14 per cent of nitrogen. As usually sold, it contains 

 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 elements ; it is strictly 

 a nitrogenous fertilizer, readily yielding to the action of 

 micro-organisms and to nitrification. On account of its 

 fermentable nature, it is a quick-acting fertilizer, and is 

 one of the most valuable of the organic materials used as 

 manure. It gives the best returns on an impoverished 

 soil to aid crops in the early stages of growth, before 

 the inert nitrogen of the soil becomes available. Dried 



