104 



The Sweet Potato 



the most common comm.ercial fertilizers and their re- 

 spective contents of manurial constituents : 



Table XIL- 



■ Composition op the Principal Commercial 

 Fertilizing Materials. 



1 In good Thomas slag at least 80 per cent of the phosphoric acid should 

 be soluble in ammonium citrate, i. e., available. 



2 Cotton-hull ashes contain about 10 per cent of lime ; unleached wood 

 ashes, 30 to 36 per cent; and leached wood ashes, 35 to 40 per cent. 



