July I, 192° 



Universality of Field Heterogeneity 



293 



The results are of unusual interest. In 1905 and 1907 the correlation 

 between yields of grain are unusually high, falling only slightly below 

 three-fourths of perfect correlation. The correlations for yields of straw 

 and for both grain and straw are of medium value in those two years. 

 In 1906, however, the correlations for all the characters are of a very low 

 order; and any one of them taken alone might not be considered signifi- 

 cant in comparison with its probable error, which has been calculated 

 on the basis of 103 plots, the number actually involved in the calcula- 

 tions. 



Apparently the unusual moisture conditions of 1906 tended to oblit- 

 erate the differences in the field to which the individuality of adjoining 

 plots was due. 



That the unusual weather had a profound influence on the yield of 

 the plots is shown by Table II, in which the means, standard deviations, 

 and coefficients of variation for the yield of the individual plots are set 

 forth.i 



Table II. — Means, standard deviations, and coefficients of variation for the yield of ragi 

 at Hehbel, near Bangalore, Mysore State, India 



[Yield expressed in pounds per i/io -acre plot] 



Year. 



1905 

 1906 

 1907 



Grain. 



192. 8 

 136.6 

 165.0 



Stand- 

 ard devi- 

 ation. 



31-5 

 47.1 



48.3 



Coeffi- 

 cient of 

 vari- 

 ation. 



16. 3 

 34-5 

 29-3 



360.8 

 191. 6 

 295-4 



Stand- 

 ard devi- 

 ation. 



82.0 

 80.2 



Coeffi- 

 cient of 

 vari- 

 ation. 



41. 2 

 42.8 



27. I 



Total yield. 



553-5 

 328.1 

 460. 4 



Stand- 

 ard devi- 

 ation. 



190.3 

 127.4 

 126. 9 



Coeffi- 

 cient of 

 vari- 

 ation. 



34-4 

 38.8 

 27. 6 



The means show that yield of both grain and straw was much lower 

 in the abnormally wet year than in either of the others. The standard 

 deviations are of course largely influenced by the actual magnitudes of 

 the yields and are, in consequence, difficult of interpretation. The rela- 

 tive variabilities, as measured by the coefficients of variation, are more 

 orderly. They show that for grain, straw, and total yield the variability 

 of the individual plot yields is greater in the wet year. 



Thus the influence of the wet season has not been to make the yield 

 of all the plots alike. It has tended to decrease yield and to increase 

 relative variability from plot to plot. But at the same time it has 

 tended to screen certain factors which in drier years have a marked 

 influence on the individuality of the plots. 



Further analysis is not desirable without more detailed information 

 concerning the plots. From the information at hand it seems quite 



1 These constants are obtained by weighting in an (n-i)-fold manner, since this was the method followed 

 in obtaining the constants for the heterogeneity coefficient. 



