Dec. i, 1920 Permanence of Differences in Experimental Plots 339 



shown elsewhere (j) that this field, which had lain in grass for many 

 years, is highly heterogeneous, showing correlations between adjacent 

 plots of r = o.6i to r = o.83- 



The conditions for corn production differed very greatly in the three 

 years. Thus the constants for yield were : 



Yield is over twice as heavy in the second and third years as in the 

 first. The variability in yield as measured by the coefficient of variation 

 is far lower in the second and third years than in the first. 



Computing the correlations between the yields for the three years, 

 we have the following results: 



For 1895 and 1896, r= -0.354 0.054, r/E r =6.6. 



For 1895 and 1897, r= 0.221 0.059, r/E r =3.8. 



For 1896 and 1897, r= +o.8i8o.o2o, r/ r =4o.i. 



There is a negative correlation for 1895 and 1896 and for 1895 and 

 1897 but a high positive correlation for 1896 and 1897. Thus the plots 

 which were better in the highly unfavorable year 1895 were poorer in 

 the two favorable years 1896 and 1897. Plots which were better in the 

 favorable year 1896 were also better in the favorable year 1897. 



B. THE HUNTLEY UNIFORM CROPPING EXPERIMENT 



The most extensive series of records available is that for a uniform 

 cropping experiment conducted for the past several years at the Field 

 Station of the Office of Western Irrigation Agriculture, at Huntley, Mont. 



The Himtley field lies in the Yellowstone Valley on land having a very 

 slight and uniform slope to the north. The detailed history of the field 

 prior to 1910 is not known definitely. It was probably first broken 

 from the native prairie sod in the spring of 1908. In 1909 it was planted 

 to sugar beets, but the crop was destroyed in the late summer. It came 

 under experimental control in 1910, when the major portion of it was 

 sown to oats and yielded a crop of 66 bushels per acre. In that season 

 a small tract in the northeast corner of the field was used as a machinery 

 park or stack yard and was not put into crop. This tract occupied 

 about two-thirds of the length of the first five plots in series II. It is 

 possible that this difference of treatment in 1910 may have been reflected 

 in the crop yields of 1911, but it seems hardly probable that any material 

 effects could have persisted longer. 



