SUSTAINABILITY OF WHITE CLOVER (TRIFOLIUM REPENS L.) IN SOWN SWARDS DEPENDING ON THEIR COMPOSITION, INTENSITY MOWING AND NITROGEN FERTILIZERS

The authors carried out studies at the experimental field station of Russian State Agrarian University - Moscow Timiryazev Agricultural Academy in 2008-2020. The study aimed to determine the resistance of white clover in mixtures with various types of grasses with two- and three-cut clipping treatments. In the experiment with four to five-component mixtures, the proportion of white clover reached 36-53% in the botanical composition of swards with the content of perennial ryegrass in the fourth year of life. It did not exceed 22-23% in the mixtures with cock’s foot. With the application of nitrogen fertilizers at a dose of N180, the clover content in the second year of swards was only 1-27%. With the aging of the swards, the proportion of clover in the harvest decreased. In the ninth year of life, its amount in swards with the content ofperennial ryegrass without nitrogen application decreased to 13-24%, and in agrophytocenoses with cock’s foot and with nitrogen application to 0-14%. The cock’s foot dominated in the four-component grass mixtures, but during the overwintering of 2015-2016, cock’s foot and perennial ryegrass almost entirely dropped out of agrophytocenoses. Tall fescue was a more resistant species. 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 eight years, and from varieties of Dutch selection, the yield equaled 4.07-5.24 t/ha. There were no significant differences in yield between grass-legume mixtures based on perennial ryegrass and cock’s foot. 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. The aftereffect of nitrogen fertilizers on the yield of grass-legume mixtures without the additional introduction of phosphorus and potassium was insufficiently effective. In long-term three-component swards, used from the 14th to the 24th years of life, white clover was more stable in the composition of agrophytocenoses after three-fold mowing than with two-mowing. In years with favorable atmospheric moisture conditions, the proportion of white clover in two and three mows reached 20.1-34.7 and 2.2-24.3%, respectively, and with a moisture deficit, it decreased to 0-9%. For 26 years of growing grasses, there was a significant increase in soil acidity - pHKCl decreased from 6.3 to 4.91-5.36, which negatively affected the resistance of clover as the herbage was aging.

white clover, grass/legume mixtures, nitrogen fertilizers, botanical composition, longevity, productivity

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