An analysis of spatial similarity in the variability of yields of winter wheat (Triticum aestivum L.) cultivars in Western Poland

The study makes use of yields of winter wheat (Triticum aestivum L.) cultivars obtained in a series of Post-Registration Variety Testing System, experiments conducted in 2006-2008 at 12 locations of diverse edaphic and climatic conditions of Western Poland. The experiments were carried out at two intensity levels in two replications. The paper presents an analysis pertaining to the intensive level of cultivation, which differed from the standard cultivation in nitrogen fertilization higher by 40 kg ha(-1), full chemical protection against fungal diseases, application of growth regulator and in foliar spray of the plants with multi-nutrient preparation. The experiments were set out in a split-block design. The trials involved the following 23 cultivars of winter wheat: `Bogatka', `Dorota', 'Finezja', 'Flair' 'Fregata', 'Kobiera', 'Kris', 'Legenda', 'Mewa', 'Nadobna', 'Nutka', 'Rapsodia', 'Rywalka', 'Sakwa', 'Sukces', 'Smuga', 'Tonacja', 'Trend', 'Turnia', 'Wydma', 'Zawisze, 'Zyta'. The statistical study started with an analysis of the original matrix of correlation between 12 experimental sites, consisting in formation of cores composed of pairs of locations described by the highest correlation coefficients. Next, factor analysis was performed, the aim of which was to diminish the dimensions of the correlation matrix. Based on the Kaiser criterion and the Cattell scree test, factors were selected whose Eigen values exceeded 1. The analysis of the primary correlation matrix and the designated cores for pairs of locations indicate existence of three large subregions: a southern, northern and seaside subregion, as well as of four microregions around Nowa Wies Ujska, Wyczechy, Kroscina Mala and Maslowice. Geographically, the subregions stretch from the south-west in the north-eastward direction. The factor analysis has allowed us to divide Western Poland into three subregions: southern, northern and the microregion of Nowa Wies Ujska, differing with respect to the variability and ranking of yields of the winter wheat cultivars. It has been suggested that when choosing a cultivar, the farmer should take into account both the list of varieties recommended for a given area and their performance at the experimental station within the pertinent subregion, a site which is characterized by soil and climatic conditions similar to those prevailing at the target area. The soil type proved to be the environmental factor of paramount importance in determining winter wheat yields.