COMPARISON OF HARVEST INDEX AND GRAIN STRAW-RATIO WITH APPLICATIONS TO WINTER OILSEED RAPE

To compare the statistical properties of harvest index and grain/straw-ratio their variabilities (expressed by the relative measure coefficient of variation), their skewnesses and kurtoses have been compared theoretically. With regard to variability, the harvest index exhibits a clear superiority (= smaller variability) compared to the grain/straw-ratio. For skewness and kurtosis no such generally valid relationships exist. But, for the range of the empirically most relevant parameter values one obtains approximately equal numerical values for skewness as well as for kurtosis of harvest index and grain/straw-ratio. Finally, the theoretical results and conclusions have been checked and applied to the experimental data sets from a field trial with ten European cultivars/lines of winter oilseed rape.