178 



THE ROTHAMSTED EXPERIMENTS. 



with mineral manure alone. The first column shows the 

 estimated average annual increased yield of nitrogen per acre 

 in the crops ; the second the estimated annual loss of nitrogen 

 as nitric acid by drainage ; the third the estimated annual 

 excess of nitrogen in the surface-soil over that on plot 5 with 

 the mineral manure alone ; and the last column shows the 

 relation which the excess in the soil bears to 100 increased 

 yield of nitrogen in the crops. 



The plots were manured as follows : — 



Plot lb. 



10. Ammonium-salts = 86 nitrogen. 



and superphosphate, 

 superphosphate and soda. 



n and potash, 



ii and magnesia. 



ii soda, potash, 



magnesia. 

 it soda, potash, 



magnesia. 



and 



and 



TABLE 50.— Experiments on Wheat. Estimated Nitrogen per acre 

 per annum, 30 years, 1851-52 to 1880-81. 



Nitrogen 

 in the crop. 



Loss of 

 nitrogen in 

 drainage. 



It is seen that the increased yield of nitrogen in the crops 

 varied exceedingly with the same amount supplied in manure, 

 according to the supply of mineral constituents. Plot 10, 

 with the ammonium-salts alone, gives the smallest increased 

 yield of nitrogen in the crop ; and plots 7 and 9, with the 

 most complete mineral manure, each gives more than twice 

 as much ; the other plots giving intermediate amounts. 



The order of the estimated loss of nitrogen by drainage is 

 almost the converse of that of the increased yield in the 

 crops. Plot 10, which gives the least increased yield in the 

 crop, shows the greatest loss by drainage ; and plots 7 and 9, 

 which yield the greatest increase in the crops, show the least 

 loss by drainage. 



