Dec. i, i 9 x&amp;gt; Permanence of Differences in Experimental Plots 349 



TABLE IX. Comparison of correlations between different yields of alfalfa with correla 

 tions between yields of alfalfa and yields of other crops 



It is clear, therefore, that either stand or specific adaptation of the 

 individual plots to alfalfa influences to an unusual degree the closeness 

 of correlation between the yields of the plots of alfalfa in the different 

 years. 



In the first crop of ear corn (1915) we find higher yields of ear corn in 

 1916, a negligible difference in the yield of oat grain and straw and total 

 yield in 1917, higher yield of silage corn in 1918, and slightly but not 

 significantly higher yield of barley grain, straw, and total yield in 1919 

 following higher yield of corn in 1915. 



Turning to the constants for ear corn in 1916, we note that higher 

 yields of grain in this year are followed by higher yields of oat straw 

 and grain in 1917 and of silage corn in 1918, and by slightly higher 

 yields of barley grain and straw in 1919. 



-The average value of the correlation between the yield of ear corn 



in 1915 and the yield of other crops during the eight years is +0.167, 



whereas that for ear corn in 1916 and other crops is +0.486. These 



averages include the correlations .for alfalfa, which are, as shown by 



&amp;gt; Table VIII, high for the crop of 1916. 



Considering the correlations for oat straw, grain, and total crop on 

 the several plots in 1917 and the yields of silage corn in 1918, we find 

 that higher values of each of these measures of capacity for oat produc 

 tion are on the average followed by slightly, but perhaps not signifi 

 cantly, higher yields of silage corn in 1918 and generally by higher 

 barley yields in 1919. 



For the oat yields the average correlations with other crops are : for 

 straw, +0.202; for grain, +0.289; an d for total yield, +0.293. 



The correlations of the yields of silage corn with the yields of the 

 preceding crops are, with one exception, positive in sign. The average 

 value for the eight years is +0.226. 



The averages of the correlations between barley yields and the yields 

 of other crops on the same plots during the eight years of the experiment 

 are +0.141 for grain, +0.086 for straw, and +0.126 for total yield. 



