THE INFLUENCE OF COVERLESS SOWING TIME OF RED CLOVER ON ITS DEVELOPMENT AND SEED YIELD
Red clover (Trifolium pretense L.) is a highly valuable forage plant. According to the recommendations of a number of authors, red clover sowing dates in the Primorskiy Region coincide with the sowing dates of cover crop, i.e. early spring under-cover sowing is performed. No studies on the time of coverless sowing of red clover under the conditions of the region were carried out. The research goal was to study the impact of coverless sowing time of red clover on its development and seed yield. The weather conditions of the growing season have a significant impact on the yield of cultivated crops. The plants are particularly sensitive to moisture and heat at the stages of early development and active growth. The plant density and seed yield of red clover were taken into account in the experiment. On the year of sowing, red clover plants were exposed to severe conditions of moisture on summer months combined with high temperatures during the second half of summer which led to a loss of plants from the grass stand. A moderate linear relationship was found (in 2018: r = 0.46; in 2019: r = 0.62) of the duration of the “rosette formation - seedling” stage and the accumulated temperatures for the same period on the years of research. The greatest loss of red clover plants on the first year of life was observed during the growing season of 2018 in the range from 70.6% to 95.7% regardless of the variety. During the growing season of 2019, from 30.4% to 91.9% of ref clover plants were lost regardless of the variety. The maximum seed yield of 202.4 kg ha was obtained in the control variant. In all varieties, the highest seed yield was obtained at the first sowing period - in the third ten-days of May.