PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

The main legume component of pasture grass mixtures is white clover. However, under conditions of increasing climate aridity, its resistance in the composition of grass stands decreases. The study aimed to determine the resistance of white clover in mixtures with various types of grasses of Russian and Dutch selection with three-time cutting of herbage. The studies were carried out in 2008-2019 in the field experiment at the Russian State Agricultural University – Moscow Agricultural Academy named after K.A. Timiryazev (Moscow, Russia). In the experiment, four grass mixtures were studied with the participation of white clover with an annual application of N₁₈₀ and without the use of nitrogen fertilizers. The proportion of white clover reached 36-53% in the botanical composition of herbage with the participation of perennial ryegrass in the fourth year of life and did not exceed 22-23% in the grass mixtures with cock's foot. With the application of nitrogen fertilizers at a dose of N_180, the participation of clover in the second year of herbage was only 1-27%. In the ninth year of life, its amount in herbage with the participation of perennial ryegrass without nitrogen application decreased to 13-24% and in agrophytocenoses with cock's foot and with nitrogen application to 0-14%. The yield of grass mixtures composed of grass varieties of Russian selection amounted to 4.16-5.52 t/ha of dry weight on average for 8 years, and from varieties of Dutch selection, the yield equaled 4.07-5.24 t/ha. With the introduction of nitrogen in a dose of N₁₈₀ on grass/legume herbage, the yield increased by only 31% and the return on fertilizers by yield increases was low, making up 4.6-8.9 kg of dry matter per 1 kg of nitrogen.