PHOSPHATIC MANURES 145 



for bone meal, but steamed bone flour, on 

 the other hand, has had a considerable 

 amount of its gelatine removed by the action 

 of superheated steam, and this has resulted 

 in a large reduction in the percentage of 

 nitrogen. But both these forms of bone are 

 found to be comparatively slow in their 

 action ; in fact it is probable that a con- 

 siderable proportion both of the phosphates 

 and nitrogen is never utilized by plants, 

 or utilized so slowly as to be practically 

 valueless. It cannot be recommended, there- 

 fore, that at present prices bones in any 

 form should be employed wherever cheaper 

 and more efficient substances can be 

 obtained. 



Pure bone meal holds up to 50 per cent, 

 of total phosphates and about 4 per cent, 

 of nitrogen, and if the former be valued at 

 Is. 3d. per unit the approximate value of 

 phosphate in basic slag and if the nitrogen 

 be similarly valued at lls. 8d. per unit 

 namely, the price per unit of nitrogen in 

 sulphate of ammonia the value of a ton 

 works out at 5, 9s. 2d. For something 

 like this price bone meal can at present be 

 purchased ; but there is no doubt that in 

 the great majority of cases a better return 

 will be obtained from a similar expenditure 



