ECOLOGICAL PLASTICITY OF WINTER WHEAT VARIETIES DEPENDING ON ROOT NITROGEN NUTRITION IN THE EASTERN FOREST-STEPPE OF UKRAINE

Purpose. Evaluate the adaptability of modern winter wheat varieties by environmental parameters and determine the level of productivity depending on the weather conditions of the year, the basic fertilizer system and the level of nitrogen nutrition. Methods. Field, statistical and mathematical analy­sis. Results. The results of studies of ecological plasticity indicators, homeostatic and yield stability of mo­dern winter wheat varieties depending on the doses of nitrogen nutrition against the background of the main application of N30P30K30 in the conditions of the Eastern Forest-Steppe of Ukraine du­ring 2016–2018 are presented. A specific response of varieties to doses of root nitrogen fertilizing was revealed depending on the development of crops in the autumn, the time of the growth-resumption in spring and weather conditions du­ring the spring-summer period. For the studied varieties, the indicators of homeostaticity (Hom) were determined, which made it possible to evaluate the varieties by their suitability for cultivation in the region. Assessment of the agronomic stability of the tested winter wheat varieties showed a high level of realization of the yield potential, which in the cont­rol variants (without fertilizer) was 86.7%. On the variants of root nitrogen fertilizing of plants at the stage of spring tillering (N20, N40, N60), this indicator varied from 85.6 to 87.4%. Conclusions. The highest yield (5.77–7.01 t/ha) was obtained from the variety ‘Epokha Odeska’ with a positive genotypic effect (0.16–0.43 t/ha). Varieties ‘Epokha Odeska’ and ‘Statna’ can be considered as intensive because over the years they had a higher yield and a pronounced reaction to growing conditions. Over the years of research with all types of ferti­lizers ‘Smuhlianka’ variety turned out to be the most valuable in terms of the smallest yield fluctuation (0.46–0.61 t/ha) and coefficient of variation (V = 3.8–5.2%), high values of homeostaticity (Hom = 11.57–15.93) and agronomic stability of the realization of the productivity potential (As = 94.8–96.2%). Moreover, the application of different doses of nitrogen did not affect the manifestation of the stability of this variety. In general, the variety ‘Smuhlianka’ turned out to be more stable and economically valuable in comparison with the varieties ‘Epokha Odeska’ and ‘Statna’, which had potentially higher productivity, but with its large fluctuation