126 SOILS AND FERTILIZERS 



ern latitudes a little time before seeding, the nitrogen 

 becomes available for crop purposes. Oil meals, as 

 cottonseed and linseed, containing a high per cent, of 

 oil are much slower in decomposing than those which 

 contain but little oil. It is better economy to feed the 

 cake to stock and use the manure than to apply the 

 cake directly to the land. Occasionally however 

 cottonseed meal has been so low in price that its use 

 as a fertilizer has been admissible. 



A ton of cottonseed meal costing $20 and containing 

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

 nitrogen would be equivalent to 13.1 cents per pound 

 for the nitrogen, which is frequently cheaper than 

 purchasing some other nitrogenous fertilizer. 



158. 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. 



One of the methods employed to detect, in fertili- 

 zers, the presence of inert forms of nitrogen as leather, 

 is to digest the material in prepared pepsin solution. 50 

 Substances like dried blood are nearly all soluble in 

 the pepsin, while leather and other inert forms are 

 only partially so. The solubility of the organic nitro- 

 gen in pepsin solution determines, to a great extent, 

 the value of the material as a fertilizer. 51 



Soluble in prepared 



pepsin solution 

 Per cent, of nitrogen. 



Dried blood 94. 2 



Ground dried fish 75.7 



Tankage 73.6 



Cottons eed meal 86.4 



Hoofand horn meal 30.0 



Leather 16.7 



