42 Fertilizers 



GARBAGE TANKAGE 



While this material is considered a low-grade product, 

 it is, nevertheless, important because the supply is in- 

 creasing annually. It is manufactured from kitchen 

 wastes of the cities, sometimes by drying, sometimes by 

 partial charring, but more often it is a by-product after 

 treatment to extract oils and greases. However derived, 

 it is very variable in composition and its value as a fer- 

 tilizer differs with its content of the elements of plant-food. 

 It is now used to considerable extent in the manufacture 

 of commercial fertilizers and sometimes as an absorbent 

 in stables, but for this purpose it lacks the desired qual- 

 ity of cleanliness and often carries disagreeable odors. 

 Analyses show that it may contain as high as 2.5 to 3 

 per cent of nitrogen, 1.5 to 3 per cent of phosphoric acid 

 and .75 to 1.5 per cent of potash. 



LOW-GRADE NITROGENOUS PRODUCTS 



Other products which contain a high content of nitrogen 

 are frequently used. These, because of their low rate of 

 availability, constitute a separate and distinct class. 



Horn meal, or ground horn, is reasonably uniform in its 

 composition or content of nitrogen. It contains as high 

 as 10 or 12 per cent of nitrogen, but it is slow to decay 

 when used in its natural state, and, therefore, is not re- 

 garded as an economical source of this element, unless 

 it can be obtained at a low price. 



Leather meal is another product which is rich in nitrogen, 

 but which is so slow to decay that its use in the natural 

 state is not recommended. One object in making leather 

 is to render it resistant to the conditions which promote 



