SECTION V.-BONE MANURES 



Bones. So far as their origin is concerned, bones have been 

 described on p. 72. Previous to being degreased, bones 

 are of little value for fertilizing purposes. After bone fat has 

 been removed, bones can be ground up to various degrees of 

 fineness. Bones that have had the grease removed, but are 

 still rich in nitrogenous organic matter, are tough and 

 difficult to grind, and are generally put upon the market as 

 a coarse meal. Those qualities of bone which have not 

 merely been degreased, but have been also partly deprived 

 of their gelatinous material, contain far less fibrous organic 

 matter, are somewhat porous, and grind easily to a very 

 fine powder. There are about three different sorts of bone 

 meal and bone dust to be found on the market. The best 

 quality bones, after having their grease removed, contain 

 about 5 % of nitrogen, equal to a little over 30 % of gelatinous 

 matter, 45 % of calcium phosphates and 15 % of water, the 

 residue being a little calcium carbonate and small traces of 

 other compounds, amounting on the whole to 5 or 7 %. 

 The lower qualities of bone meal, obtained from bones con- 

 taining higher proportions of calcium phosphate and lower 

 proportions of organic matter, may often be met with con- 

 taining about 4 % of nitrogen and 45-50 % of tri-calcium 

 phosphate. Steamed bone flour may contain anything from 

 1 to 3 % of nitrogen, and from 50 to 60 % of tri-calcium 

 phosphate, some of the finest bone flours containing about 

 iJ-2 % of nitrogen and 55 % of tri-calcium phosphate. 

 The use of bones containing 30 % gelatinous matter as manure 

 is a wasteful process ; bones containing the lower proportions 

 of nitrogenous matter decompose rapidly in the soil and are 

 therefore to be preferred. Gassmann considers that the 

 phosphate in bones is a carbonic apatite, Ca 10 (PO 4 ) 6 .CO 3 

 (see p. 120). 



