NITROGEN CONTENT IN SOIL AND NITRATE REDUCTASE ACTIVITY IN WINTER WHEAT LEAVES WITH THE USE OF NITROGEN FERTILIZERS

The purpose of the study is increasing the efficiency of using nitrogen fertilizers and its effect on nitrate-reducing capacity of the leaf apparatus. The research was conducted in 2016-2018 in the Central zone of the Samara re-gion. The predecessor is complete fellow. Svetoch winter wheat elite seed varieties were used for sowing. Seeding was carried out in the experimental fields of the laboratory «Agroecology» of the Samara state University. Nitrate and ammonium nitrogen content in soil layer of 0-30 cm depth was estimated before planting and after plant nutri-tion with nitrogen fertilizers in regard to the growth phases (tillering, elongation and heading), the content of nitro-gen, protein and nitrate reductase enzyme activity in leaves during plant development. Dynamics changes of nitro-gen content in the soil and after fertilization with nitrogen shows that during vegetation period of plants, the amount of nitrogen is sufficient for their growth. As the phenological phases of plants change, the content of nitrogen and protein in winter wheat leaves increases, and activity of the enzyme nitrate reductase lifts, which catalyzes nitrate regeneration to nitrite. The value of the activity of the enzyme nitrate reductase in leaves can serve as a criterion for evaluating the availability of plants with the nitrate form of nitrogen. In future, the activity of this enzyme can be used as an indicator of optimizing nitrogen nutrition of plants aimed at metabolic processes. The use of various nitrogen fertilizers, and to a greater extent ammonium nitrate, increased the supply of plants with nitrogen, which is later used by them in the reutilization of nitrogen from leaves to the emerging seed, thus contributing to quality of grain.