36 



EXPERIMENTS UPON WHEAT 



TABLE XVI. Experiments on Wheat, Broadbalk Field. Average Produce 

 of Grain and Straw per acre the first 8 years (1844-1851), and over the 

 successive W-year periods (1852-1911) inclusive. 



A. Maintenance of the yield under Continuous Wheat 

 growing on the same land. 



The curves in Fig. 2 show the fluctuations in the yield of 

 total produce for the first eight-year and six ten-year periods 

 from the beginning of the experiment on certain of the plots 

 -Plot 3, which is unmanured ; Plot 2, which receives farm- 

 yard manure every year ; Plots 6 and 7, which receive a 

 complete artificial manure containing varying quantities of 

 nitrogen ; and Plot 10, which receives nitrogen only. 



Considering the unmanured plot first, it will be seen that 

 while there is evidence of a smull decline in production for the 



