Optimisation of soybean sowing dates in the Central Chernozem Region as a factor in realising the genetic potential of the variety

The study was conducted to determine the optimal sowing date and the effectiveness of mineral fertilizer application in the cultivation of the Osmon soybean variety. The work was carried out in 2022-2025 in the Kursk region. The field experiment design included the following options: sowing date (factor A) – early (the period of sowing early spring crops), medium (the period of sowing late spring crops), late (after the period of sowing late spring crops); mineral fertilizers (factor B) – no fertilizers, N 30 P 30 К 30 . The experimental plot was located on typical chernozem with an average humus content, increased mobile phosphorus content, and high mobile potassium content. The weather conditions of the experiment were quite varied. One month after sowing, the number of leaves in later-sown plants significantly increased, and the effectiveness of fertilizers decreased from 80 to 12 % as the sowing date was delayed. The timing of the onset of soybean development phases was directly dependent on the air temperature during crop development (r=0.87) and soil temperature at a depth of 5 and 15 cm during sowing (r = 0.57 and r = 0.55). With an early date, the biomass size one month after sowing decreased by 2.5 times compared to the average, while with a late date, it increased by 1.9 times. Two months after sowing, the difference remained. On average, over the years of research, the soybean yield varied from 2.35 to 3.02 t/ha. When sowing was postponed to later dates, it increased from 2.45 t/ha with early sowing, 2.73 t/ha with average sowing, and 2.93 t/ha with late sowing. The use of mineral fertilizers ensured a reliable increase in yield on average in the experiment of 0.21 t/ha, or 8 %. Mineral fertilizers and sowing time had approximately the same impact on soybean yield (47.5 % and 43.8 %, respectively).