SUMMARY 219 



167. Leather, Hair, Wool Waste, Hoof, and Horn. These 

 materials are waste products from various industries and 

 are very slow acting, practically worthless forms of nitro- 

 genous fertilizers when used without previous treatment. 

 Leather, hoof, and horn are sometimes steamed or roasted 

 and ground, and even treated with sulphuric aeid, when they 

 make a fair grade of fertilizer. Leather contains about 8 

 per cent, nitrogen, hair 13 per cent., wool waste 5 to 10 

 per cent., horn and hoof 10 to 15 per cent. 



Most of these materials, however, are used by the fertilizer 

 manufacturers in the preparation of "base goods." They are 

 treated with sulphuric acid along with rock phosphate. 

 The nitrogen is thereby partly converted to ammonium sul- 

 phate or some more available form of nitrogen than the 

 original non-decomposible protein form. This mixture of 

 acid phosphate and "chamber process" nitrogenous material 

 forms a "base" for fertilizer mixtures. 



168. Summary. — Nitrogen is the most expensive element 

 that the farmer has to buy, although not the most important. 

 It occurs in various forms, nitrate, ammonia, and amine 

 or protein, and the availability is roughly in that order. 

 Sodium and calcium nitrates are the best forms for rapid 

 action. The former occurs naturallv; the latter is made 

 from the nitrogen of the air. Both of them, aside from 

 supplying nitrogen to the plant, act on the soil to set free 

 potassium. Sodium nitrate has a bad residual effect on 

 soils after long continued use. Calcium nitrate, however, 

 has no bad effect whatever. Both tend to neutralize soil 

 acidity. 



Ammonium sulphate is very readily available since it 

 nitrifies rapidly. The residual effect, however, is to leave 

 the soil acid. Cyanamid is another manufactured product 

 using the air as a source of nitrogen. It is an excellent 

 fertilizer, leaving a calcium residue in the soil and thereby 

 being of benefit. 



Animal and plant nitrogenous materials are of varying 

 availability and value. Dried blood, tankage, fish scrap, 

 and cottonseed meal being better than leather, hair, ivool 

 waste, hoof, and horn. These materials all have nitrogen 



