216 CEOPS GROWN IN ROTATION 



of farmyard manure or its equivalent during the rotation. The 

 losses of phosphoric acid and potash would be similarly made 

 up, though it is well also to use about 50 Ib. of phosphoric 

 acid per acre for the Swede crop, which is specially dependent 

 on a large quantity of available phosphoric acid. 



7. As the standard of farming is raised, however, it is 

 necessary to give further supplies of nitrogen and correspond- 

 ing increases in the supplies of phosphates and potash. 



REFERENCES 



" Rotation of Crops." Jour. Roy. Ag. Soc., 55 (1894), 585. Rothamsted Memoirs, 

 Vol. VII., No. 7. 



