The Influence of Modern Complex Fertilizers and Growth Regulators on the Formation of Productivity of White Sweet Clover

The research aimed to study the effect of growth regulators and complex fertilizers on the yield of green mass and seeds of sweet clover. The work was carried out in 2019–2021 in the south of the forest-steppe zone of the Middle Volga region. The object of the research was the Srednevolzhsky annual variety of white sweet clover. To assess the effectiveness of biologically active preparations, seeds were treated (the consumption rate of the working solution was 10 L/t) and foliar feeding (300 L/ha) was carried out in the phases of the beginning of budding and flowering according to the following design: no treatment (control–water), Mival Agro (5 g/t; 15 g/ha), Vitanoll N (0.5 L/t; 2.0 L/ha), Vitanoll PK (0.5 L/t; 2.0 L/ha). On average, over the years of research, when using the studied preparations, the increase in productivity of the aboveground biomass of white sweet clover in the phase of mowing maturity compared to the control increased by 15.2–20.4% and dry matter to 17.3–24.1%. In the phase of full flowering, the yield of green mass in the control was less than in the experimental (Mival Agro, Vitanoll N, Vitanoll PK) by 16.4–17.8% and in terms of dry matter collection by 14.6–20.0%. The highest increases in green mass and dry matter yields in the experiment (17.8–20.4%; 20.0–24.1%, respectively) were observed in the variant with treatment with the complex fertilizer Vitanoll N. Seed productivity of the control variant on average over the years of research amounted to 459.9 kg/ha, and the use of the studied preparations led to its increase by 9.4–43.1%. The greatest impact on the implementation of the seed productivity potential of sweet clover was exerted using the growth regulator Mival Agro, in which the increase in yield to the control without treatment over the years amounted to from 27.7 to 52.2%.