PHOSPHATIC MANURES 127 



of the converter. The slag and bricks are 

 subsequently ground into an impalpable 

 powder, which is the material the farmer 

 purchases and applies to his land as a phos- 

 phatic manure. As in the case of nitrate 

 of soda and sulphate of ammonia so here, 

 a farmer has to weigh very carefully the 

 advantages and disadvantages of purchasing 

 basic slag as compared with superphosphate 

 of lime. There is little doubt that super- 

 phosphate, containing as it does soluble 

 phosphate, is more rapid in its action than 

 basic slag, and, consequently, for immediate 

 effect, the former manure is to be preferred. 

 But any objection to basic slag on the score 

 of slowness of action can be overcome to a 

 large extent by looking ahead ; so that if 

 it is desired, for instance, to dress a root crop 

 with basic slag it can be applied to the land 

 some months before the time when the crop 

 will occupy the ground. During this interval 

 the insoluble phosphate of the slag will be 

 acted upon by the natural solvents of the soil, 

 so that a considerable proportion of the 

 phosphoric acid will be immediately available 

 when the plants require it. 



Except from the point of view of rapidity 

 of effect, basic slag would appear to possess 

 advantages that are superior to those associ- 



