v.] BONE FERTILISERS 157 



soil to soil. In order to make a proper choice, the 

 farmer ought, first of all, to know how much carbonate 

 of lime his soil contains, and in the light of his know- 

 ledge of that factor and of the general character and 

 climate of the soil, he will decide first whether he 

 requires a basic, acid, or a neutral phosphate, and then 

 which is the cheapest inside the selected class. 



