CHAPTER VI. 



LOW GRADE NITROGENOUS MATERIALS AND FUNCTIONS OF 

 NITROGEN. 



The nitrogenous substances discussed in the previous chapter 

 are all considered high class and valuable standard materials. 

 Some of them as the mineral compounds are immediately or al- 

 most immediately available, while the organic materials, both 

 animal and vegetable, vary in their degree of availability, but 

 stay with the crop during the whole or the greater part of the 

 season. 



The high prices of these desirable and valuable nitrogenous 

 materials have caused some of the manufacturers of commercial 

 fertilizers to seek and use cheaper sources of nitrogen. Many 

 of these cheaper materials, to be sure, are rich in nitrogen but 

 really of little value as the nitrogen is present in such forms 

 as to be inert or else too slow acting to stimulate plant growth. 

 Many of these low grade nitrogenous waste products are im- 

 ported from foreign countries yet we produce our share of them 

 in this country. They are made up of wastes from the manu- 

 facture of silk, wool, feathers, combs, hair, skins, sugar and 

 some few are derived from vegetable sources. The materials 

 most commonly used will be discussed. 



Raw Leather Meal. — This product contains about 8 per cent, 

 nitrogen which is in a form that is very slowly utilized by plants ; it 

 may remain in the soil for two or three years before decaying. It 

 takes such a Jong time for it to decompose that it has not much 

 value for fertilizing purposes. One of the objects in the treat- 

 ment of leather is to prevent its decay and for this reason raw 

 leather may remain in the soil for a very long time before under- 

 going any change. This material is sold varying in the degree 

 of fineness from a dust to coarse particles. If it is ever used it 

 should be powdered. At best it is a tough material. 



Dissolved leather, sometimes called treated leather or extracted 

 leather, is made in Belgium. The raw leather is roasted and very 

 finely ground and treated with superheated steam which removes 



