1 86 SYSTEMS OF PERMANENT AGRICULTURE 



umes in crop rotations. To supply sufficient nitrogen for a hun- 

 dred-bushel crop of corn would require 9 tons of steamed bone 

 meal, costing about $225. 



The phosphorus in raw bone and steamed bone exists in the form 

 of the insoluble tricalcium phosphate, but because of the porosity 

 and fine division of the bone particles and the presence of decom- 

 posing organic matter in intimate contact with the extensive sur- 

 face within the pores, phosphorus is liberated quite readily from 

 bone meal, steamed bone being more active because of the removal 

 of the fat and because it is usually more finely ground than raw 

 bone. 



Acidulated bone meal. Acidulated bone meal (" acid bone ") 

 is made by adding to a ton of bone meal sufficient sulfuric acid to 

 convert a part of the insoluble tricalcium phosphate into the sol- 

 uble monocalcium phosphate, or at least into the more readily 

 available dicalcium phosphate. The bone meal thus treated is said 

 to be mildly acidulated. As an average, it contains about 140 

 pounds of phosphorus and 40 pounds of nitrogen per ton. Much 

 of the so-called " dissolved bone " sold in the fertilizer trade is made 

 from phosphate rock, and this is no detriment to the product so 

 far as the soluble portion is concerned, but the insoluble portion 

 is more rapidly available if derived from bone than from rock. 

 In the acidulated and most readily available form, phosphorus 

 sells at about 12 cents a pound. 



Other bone products include bone black, dissolved bone black, 

 and bone ash. Tankage from the packing houses varies from 

 nearly pure bone to a high percentage of nitrogenous organic 

 matter, including dried blood, meat, and mixed offal. Some further 

 data will be found under nitrogen fertilizers. 



Three principal kinds of phosphorus fertilizer are derived from 

 phosphate rock. These are (i) the fine-ground natural rock, 

 (2) acid phosphate, and (3) double superphosphate. 



Natural phosphates. Natural phosphate beds are widely dis- 

 tributed over the earth, some of the most important deposits being 

 in Tennessee, South Carolina, Florida, and Canada, also in France, 

 Belgium, Norway, Spain, and North Africa. The present annual 

 production of the world amounts to about three million tons, of 

 which two million tons are produced in the United States, about 



