160 



Fertilisers 



[PT. Ill 



siderable increase in yield, but a still further increase is 

 obtained by suppljdng potassium salts in addition 

 (Table VI). 



Table VI. Effect of manures on the yield of barley. 

 Rothamsted: average 60 years, 1852-1911 



Another instance is afforded at Saxmundham (Table 

 VII). The soil is heavy and potash was not expected to 

 give a return, nor did it so long as the yields were low. 

 But directly phosphates are added the yield goes up and 

 the potash-needing plants beans, peas and lucerne 

 can now increase beyond the capacity of the soil supplies 

 of potash. Fresh additions of potash are therefore neces- 

 sary for these crops, but not, however, for barley or 

 wheat. 



Table VII. Effect of potassic manures on croups. 

 Saxmundham : average yields 4 years, 1910-1913 



1 6 years, 1903-1908. 



