EXPERIMENTS IN FIELD PLOT TECHNIC 



69 



to determine the effect on variability of adjusting the yields of the 

 120 plots of Kherson, on the basis of those of the 120 plots of Red 

 Rustproof adjoining them, and those of the 120 plots of Red Rustproof, 

 on the basis of the yields of the adjoining Kherson plots. In this 

 adjustment the yield of each plot is divided by the plot value of the 

 adjoining plot, and the method corresponds to method II used by 

 Kiesselbach in the experiment cited above (see Table 29). The results 

 of the yield adjustment are shown in Table 39. 



The adjustment of plot yields by means of check plots of a va- 

 riety distinctly different in type resulted in a decided increase in plot 

 variability, even though the plot values used were determined in each 

 case by the yield of the immediately adjacent plot. If the yields 

 of the Kherson and the Red Rustproof plots had been perfectly ac- 

 curate measures of the productivity of the soil, the plot values of the 

 adjacent plots would have been almost the same in each of the 120 

 locations, and the adjustment of the yields of either variety by those 

 of the other would have reduced variability almost to zero. Instead, 

 variability was actually and very decidedly increased, because the sec- 

 tions of the field which gave relatively high yields of Kherson, gave 

 relatively low yields of Red Rustproof, and vice versa, in many cases. 

 In fact, there was very little relation between the productivity of a 

 portion of the field as determined by a Kherson check, and the pro- 



60 to 70 



70 to 80 



80 to 90 



90 to 100 



100 to 110 



110 to 120 



120 to 130 



130 to 140 



140 to 150 



150 to 160 



160 to 170 



170 to 180 



Total 



B B B B 



O O O O 



O O O O 



O5 O rH OJ 



rH OJ 03 01 



B B B B 



O O O O 



02 



oooo 



O O O O 



Tt< CO Z> 



FIGURE 7. CORRELATION BETWEEN YIELDS OF KHERSON CHECK PLOTS AND 

 YIELDS OF ADJACENT RED RUSTPROOF CHECK PLOTS, IN OATS VARIETY AND 

 STRAIN TESTS 1921. 



r= +.162 .060. 



