NONPARAMETRIC ANALYSIS OF CULTIVAR PERFORMANCE TRIALS - EXPERIMENTAL RESULTS AND COMPARISON OF DIFFERENT PROCEDURES BASED ON RANKS

Cultivar performance trials are usually analyzed by analysis of varian ce techniques. In the field of practical applications, the required si mplifying assumptions may often not be fulfilled. Nonparametric method s based on ranks avoid this difficulty and provide a viable alternativ e to parametric procedures. The objective of this study was to compare four nonparametric procedures (Bredenkamp, Hildebrand, Kubinger, and van der Laan-de Kroon) and the parametric analysis of variance with ea ch other for extensive data sets from German official registration tri als (1985-1989) with winter oilseed rape (Brassica napus L.), faba-bea n (Vicia faba L.), oat (Avena sativa L.), fodder beet (Beta vulgaris L .), and sugar beet (B. vulgaris). The van der Laan-de Kroon method is based on the crossover concept of interaction (different rank orders), while the other methods are based on the concept of deviations from a dditivity of main effects. The methods were compared using the numeric al values of the test statistics. For the sources cultivars, locations , and interactions one obtains these relationships: ANOVA greater than or equal to Hildebrand congruent to Kubinger > van der Laan-de Kroon > Bredenkamp. If the assumptions for parametric methods cannot be acce pted, the van der Laan-de Kroon method is recommended for the crossove r interaction concept, while the Hildebrand or Kubinger method (both o f which are approximately equivalent) should be applied for the usual interaction concept. The Bredenkamp method cannot be recommended.