Features of grain productivity formation of winter rye (Secale cereal L.) depending on nitrogen fertilizers

Topicality. Determination the complex influence of predecessors, sowing dates and mineral nutrition on the grain productivity of modern winter rye varieties is relevant, since it allows to more fully reveal the biological potential of plants and significantly increase the winter rye yield in the Steppe zone of Ukraine. Issues. Winter rye is an important and valuable crop. However, in recent years, due to significant climatic changes in the Steppe zone, research on the optimization of technological methods of its cultivation was practically not conducted. Thus, the current problem in crop production is to determine the complex influence of predecessors, sowing dates and fertilizers on the productivity formation of modern winter rye varieties in order to more fully use the biological potential of plants. This task has both practical and theoretical significance. Purpose. To study the peculiarities of the grain productivity formation of different winter rye varieties depending on the predecessors, sowing dates and the level of mineral nutrition in the soil and climatic conditions of the Northern Steppe. Materials and methods. During 2019–2021, we conducted the research on the basis of the Research Farm "Dnipro" of the State Enterprise Institute of Grain Crops of NAAS of Ukraine. The research was conducted in a four-factor field trial. Stoir and Pamiat Khudoierka varieties of winter rye were sown at different sowing dates: early (September 5–10), optimal (September 20–25) and late (October 5–10). The predecessors were spring barley and sunflower, level of mineral nutrition was different. Results. In the years of our studies, weather conditions were characterized by high variability compared to long-term average data. The distribution of precipitation by months and periods of the year was rather uneven. Winter rye yield formation occurs as a result of complex interaction of productivity elements. The research clearly traced the variability in the formation of the number of productive stems per unit area and grain weight per head in plants of different winter rye varieties under the influence of weather conditions, predecessors, sowing dates and level of mineral nutrition. Thus, the maximum number of productive stems of winter rye (520 pcs/m2) was obtained in the variant after spring barley with nitrogen fertilization when Stoir variety was sown on September 20–25. When this variety was sown on September 5–10, the number of productive stems decreased by 2.7 %, and by 11.9 % for sowing on October 5–10. A similar trend was also observed in areas where winter rye was grown after sunflower. According to the research results, it was established that plant dressing with nitrogen (N45) in early spring on freeze-thawed soil increased the winter rye grain yield after spring barley by 0.11–1.05 t/ha, after sunflower – by 1.15–1.43 t/ha compared to plots where fertilizers were not applied. Conclusions. It was found that the maximum number of productive stems per area unit (520 pcs/m2) was formed by winter rye plants of the Stoir variety at sowing on September 20–25 after spring barley with application of nitrogen fertilizers. Plants of the Stoir and Pamiat Khudoierka varieties formed the largest grain weight per head 1.25 and 1.23 g, respectively. Among the winter rye varieties, Stoir variety had the maximum grain productivity when sowing was carried out on September 20–25. On average over the years of research, the highest yield was obtained in the variants with nitrogen fertilization on freeze-thawed soil after spring barley – 6.47 t/ha, after sunflower – 5.03 t/ha. In these vari-ants of the field trial, Pamiat Khudoierka variety also provided the highest level of productivity – 6.17 and 4.72 t/ha, respectively. Keywords: winter rye, varieties, fertilizers, crop dressing, yield.