346 



Journal of Agricultural Research 



Vol. XX, No. s 



Unfortunately the number of crops which can be included in Table VI 

 is rather small. The coefficients are positive in sign throughout, and in 

 all cases they are statistically significant in comparison with their probable 

 errors. The individual constants will receive attention in the following 

 discussion. 



The fact that the yields are correlated in the different years for whole 

 plots of 0.17 acre, for half plots of 0.085 acre, and for quarter plots of 

 only 0.0425 acre emphasizes the permanence of the substratum differences. 

 We now have to compare the correlations secured for these three divisions. 

 The difference in the actual magitudes of the correlations appear in 

 Table VII. The three entries, when all comparisons are possible, show: 



(1) the difference between the correlation for whole plots and half plots, 



(2) the difference between the correlation for whole plots and quarter 

 plots, and (3) the difference between the correlation for half plots and 

 quarter plots. 



The signs are positive when the correlations are larger for the larger 

 areas. 



The comparisons show that in general the correlations decrease in 

 magnitude as the areas upon which they are based are subdivided. Thus 

 1 6 of the 22 comparisons of the correlations deduced from whole plots 

 and from half plots (first entry) show a lower correlation in the half plots 

 as compared with 6 which show higher correlations in the half plots. 



TABLE VII. Differences in interannual correlations for whole plots, half plots, and 



quarter plots 



