72 FERTIUTY AND FERTILIZER HINTS 



fertilizer. It contains usually about 30 per cent, of phosphoric 

 acid in the form of phosphate of lime. It is a slow acting- 

 fertilizer and is not used extensively in this condition.* 



Bone-Ash. — When bones are burned the remaining product is 

 called bone-ash. It is not manufactured a great deal in this 

 country because of the greater value of bone-black. It is an ex- 

 cellent fertilizer and the only shipments received to-day come 

 from South America where the bones are burned to save freight. 

 In burning bones the nitrogen is driven off, so that bone-ash is 

 valuable only for the phosphoric acid it contains. It varies in 

 phosphoric acid content from 30 to 39 per cent. It is used in 

 some countries in the manufacture of fertilizers.* 



Bone Tankage. — This product is composed entirely of animal 

 matter. It is the refuse from slaughter houses and rendering 

 factories and consi.sts of meat, bone, etc. (from which the fat has 

 been extracted), and sometimes a little dried blood. There are 

 many grades of tankage put upon the market. Those tankages 

 coming under the head of bone tankage contain considerable bone 

 and small amounts of meat and sometimes dried blood. The 

 amount of phosphoric acid in tankage varies with the bone con- 

 tent. The more bone present the higher is the percentage of 

 phosphoric acid. The bone tankages range from 11^2 per cent, 

 to 20 per cent, of phosphoric acid. Those tankages falling be- 

 low 11^4 per cent, of phosphoric acid are discussed under the 

 chapter on nitrogenous fertilizer materials. The phosphoric acid 

 in bone tankages has about the same value as in steamed bone, 

 since both of these products are steamed or boiled to extract the 

 fats, etc. The bone tankages are very popular among farmers 

 in certain sections of this country. 



Dry Ground Fish. — This is also an organic source of phosphoric 

 acid from phosphate of lime. The phosphoric acid content de- 

 pends upon the amount of bones present. This product was de- 

 scribed with the fertilizer materials containing nitrogen. Suffice 

 it to say that dry ground fish carries from 6 to 16 per cent, of 

 phosphoric acid. 



