152 Agricultural Chemistry. 



per cent of phosphoric acid, and 2 per cent of potash. It 

 is too good a food material to be used as a fertilizer, as it is con- 

 sidered one of the best concentrated feeds on the market. Its 

 value as a feed is becoming more and more recognized and it is 

 only a question of time when, like linseed meal, it will no longer 

 be available as a fertilizer. 



Castor pomace is a by-product in the manufacture of castor 

 oil. It contains 5.5 per cent of nitrogen, about 2 per cent of 

 phosphoric acid and 1 per cent of potash. 



Slowly available materials. Under this head are classed such 

 materials as leather meal, hoof and horn meal, and hair and wool 

 waste. 



Leather. This is a waste product from various factories and 

 is sold as raw leather, steamed leather and roasted leather; it 

 contains about 7 per cent of nitrogen and in the soil decays very 

 slowly. When finely ground it is sometimes used to adulterate 

 fertilizing material. 



Hoof and horn meal is a by-product resulting from the mak- 

 ing of various articles from hoofs and horns; it is very rich in 

 nitrogen, carrying about 14 per cent, but decomposes very slowly 

 in the soil. 



Hair. This is another product from slaughter houses, and 

 when dry contains from 9 to 14 per cent of nitrogen. It is very 

 unavailable and should not be used in its natural condition for 

 fertilizing purposes. 



Wool waste is the waste product from the woolen mills and 

 contains from 5 to 6 per cent of nitrogen and about 1 per cent 

 of potash. It is essentially the wool fibres which have become 

 so short by repeated spinning, weaving, etc., that they will no 

 longer hold together. It is a low grade fertilizer. 



In many states all the above resistant materials are prohibited 

 from sale as fertilizers. This appears just, since in their original 

 form they decay so very slowly as to make them of little value 

 as food for plants. 



