July I, 1920 



Universality of Field Heterogeneity 



295 



Finally, Montgomery {16) has given data for both yield of grain and 

 nitrogen content on 224 plots of wheat grown at the University of 

 Nebraska in 191 1 . The plot {yj by 88 feet) had been sown continuously 

 to Turkey winter wheat for three years. 



The plat was of about average uniformity and fertility. 



When grouped in a 2 by 2 fold manner these plots of wheat have 

 been shown (5, p. 440-441, map C) to give the following correlations: 



For yield of grain, r= 0.603 ±0.029, rlEj.= 2i. 



For percentage of nitrogen, r= .ii5± .044, r/E,.= 2.59. 



Yield of grain per plot is clearly influenced by irregularities of the 

 experimental field, notwithstanding the fact that the plots are only 

 5.5 by 5.5 feet in area. The correlation- for percentage of nitrogen 

 is not certainly significant. 



9. — HOPS 



Stockberger {20) has given a series of yields for 30 rows of hops which 

 he believes to be quite typical of many thousands of acres in the Sacra- 

 mento Valley in California. The yields of these rows cover the period 

 of 1909 to 1 914. Combining the rows by twos and determining the 

 correlation between the yield of the adjacent rows of the 15 pairs for 

 each of the years, we obtain the following constants : 



Without exception the coefficients are positive in sign. In general 

 they are fairly large and indicate a substantial degree of heterogeneity 

 in this limited area. Probably the heterogeneity would have been 

 shown to be greater had it been possible to work with yields from the 

 sections of the long rows instead of with the rows as a whole. 



10. UNHUSKED RICE 



Coombs and Grantham (2) give the yield in gantangs of a series of 54 

 square plots K by X chain in dimension. 



These plots are arranged in 18 ranks and 3 files. They were har- 

 vested from a field of standing rice on which — 



the crop was extremely regular, as judged before the cutting, and it had not been 

 subjected to any attack of borer or any devastation of rats or birds. 

 177285° — 20 2 



