FERTILIZERS 25 



STEAMED BONE. 



37. Steaming bones removes the fat and gela- 

 tines, thus facilitating decay and availability, as 

 such bone can be ground finer than raw bone, and 

 thus becomes more subject to the attack of soil 

 moisture and various dissolving agents. 



Raw bone contains from 3% to 4^/2% nitrogen and 

 about 22% or 23% phosphoric acid. Steaming re- 

 duces the nitrogen and correspondingly increases 

 the phosphoric acid, so that steamed bone may run 

 as low as 1% nitrogen and as high as 25% or 30% 

 phosphoric acid. The best effect from the phos- 

 phoric acid of steamed bone is had when the bone is 

 used in connection with some ammoniate such as 

 blood, tankage or manure. Nitrogen increases the 

 efficiency of phosphoric acid, and for this reason 

 phosphoric acid from animal or vegetable sources is 

 regarded as the best, the most effective and the most 

 readily available form. If mineral phosphates are 

 used, there must be humus in the soil. (40.) 



THOMAS PHOSPHATE SLAG ( POWDER). 



38. Thomas slag, a product from iron furnaces, 

 is a good source of phosphoric acid, though not so 

 generally used as bone or rock. This material has 

 to be finely ground to be of value, as it is not acidu- 

 lated. It will analyze as high as 20% phosphoric 

 acid, usually 17%. Thomas slag also contains much 

 lime, which fact should be considered when it is 

 used in the presence of ammonium sulphate, or 

 barn manures, as the lime will drive off the am- 

 monia. An average analysis might show 17.28% 

 phosphoric acid, 46. 20% lime and iron oxide 18. 37%. 



