NITROGENOUS MANURES 133 



quick-acting a fertilizer as dried blood, but when used 

 in southern latitudes a little time before seeding, the 

 nitrogen becomes available for crop purposes. Cot- 

 tonseed or linseed meal containing a high per cent, of 

 oil is much slower in decomposing than that which 

 contains but little oil. It is grenerallv considered bet- 

 ter economy to feed the cake to stock and use the 

 manure than to apply the cake directly to the land. 

 Of late years cottonseed-meal has been so reduced in 

 price that its use as a fertilizer has been admissible. 



A ton of cottonseed-meal costing $20 and contain- 

 ing 2 per cent, of phosphoric acid and 7 per cent, of 

 nitrogen would be equivalent to buying the nitrogen 

 at 1 3. 1 cents per pound, which is frequently cheaper 

 than purchasing some other nitrogen fertilizer. 



156. Leather, Wool Waste and Hair are rich in 

 nitrogen, but on account of their slow rate of decom- 

 posing are unsuitable for fertilizer purposes. When 

 present in fertilizers they give poor field results. 



157. Solubility of Organic Nitrogenous Mate- 

 rials. — The method employed to detect, in fertilizers, 

 the presence of inert forms of nitrogen as leather, is to 

 digest the material in prepared pepsin solution. 49 

 Substances like dried blood are nearly all soluble in 

 the pepsin, while leather and inert forms are only par- 

 tially so. The solubility of organic nitrogen in pep- 

 sin solution determines, to a great extent, the value of 

 the material as a fertilizer. 50 



