NITROGEN, NITRIFICATION, NITROGENOUS MANURES 149 



165. Tankage is composed of refuse matter, as bones, 

 trimmings of hides, hair, horns, hoofs, and some blood. 

 The fat and gelatin are, as a rule, first removed by sub- 

 jecting the material to superheated steam. This mis- 

 cellaneous refuse, after drying, is ground and some- 

 times mixed with a little slaked lime to prevent rapid 

 fermentation. 



Tankage contains less nitrogen but more phosphoric 

 acid than dried blood. Owing to its miscellaneous na- 

 ture, it is quite variable in composition, as the following 

 analyses of tankage from the same abattoir at different 

 times show : M 



As a general rule, tankage contains from 5 to 8 per 

 cent of nitrogen and from 5 to 12 per cent of phos- 

 phoric acid. It is much slower in its action than dried 

 blood, and supplies the crop with both nitrogen and 

 phosphoric acid. Tankage is a valuable form of fer- 

 tilizer for garden purposes. It may also be used as 

 a top dressing on grass lands, or spread broadcast on 

 grain lands. It is best to apply the tankage, when pos- 

 sible, a few days prior to seeding, and it should not 

 come in contact with seeds. Two hundred and fifty 



