WHEAT BEST STANDS ABSENCE OF MANtJRE 195 



H'O bushels per acre on the unmanured plot in Broadbalk 

 growing wheat continuously, and with 16*9 bushels on the 

 similarly unmanured plot where wheat is grown after a bare 

 fallow. In the earleir period on the rotation field the 

 unmanured plots yielded 82 per cent, of the wheat on the 

 manured plots, but in the later period the production without 

 manure had fallen to less than 70 per cent, of that on the 

 manured plots, whereas in the corresponding later years of 

 the continuous wheat-field the production on the unmanured 

 plot has fallen to 29 per cent, of that on the manured plot. 

 It is clear that the progressive cropping out of the soil is 

 telling upon the wheat, though it will take a very long time 

 before the crop grown in rotation is reduced to the level of 

 the unmanured land that is continuously cropped with wheat. 



II. EFFECT OF THE MANURES. 



The three main plots into which the experimental field is 

 divided receive the following manurial treatment per acre : 

 O. Unmanured continuously. 



M. 3^ cwt. superphosphate, 500 Ib. sulphate of potash, 

 100 Ib. sulphate of soda, and 200 lb. sulphate of 

 magnesia for the Swedes. 



C. Minerals as on Plot M., together with 200 lb. ammo- 

 nium-salts and 2000 lb. rape cake for the Swedes. 



TABLE LXVI. Effect of Manure on Crops grown in rotation, Agddl Field. 

 Average produce per acre over the seven Courses, 1884-1911. 



Average of 7 courses. 



t Average of 2 courses. 



