EFFECTS OF DIFFERENT SEED FRACTIONS AND FOLIAR FERTILIZATION ON THE YIELD POTENTIAL OF WINTER RAPESEED VARIETIES AND HYBRIDS

The growing demand for oilseeds in global and domestic markets requires an increase in the seed yield of winter rapeseed through the optimization of cultivation practices. The aim of the study was to determine the patterns governing plant density, survival throughout ontogenesis, and seed productivity as a function of seed size and three applications of the Phitospectr preparation via foliar spraying against a background of N184P34K51S24. This article presents the results of field studies (2024–2026), based on which it was established that the use of large-sized seeds for sowing is a determining factor in optimizing plant density, ensuring the emergence of 38.6–40.0 pt./m2 and the survival of 33.5–36.7 pt./m2 prior to harvest. In contrast, sowing small seeds results in sparse stands and a yield shortfall of 0.28–0.40 t/ha of seed. The high effectiveness of the Phitospectr growth stimulator has been demonstrated when applied on a mineral nutrient background (N184P34K51S24); its action increases the vitality of plant communities by 0.7–4.4% by the end of the growing season and ensures a stable yield increase of 0.10–0.15 t/ha. It was found that the agricultural measures studied help mitigate the negative impact of stressful hydrothermal conditions, particularly the drought of 2025, when yields dropped to 2.70–3.49 t/ha compared to a maximum of 4.84 t/ha in the favorable year of 2024. Based on the results of the genotype evaluation, the Dalton hybrid demonstrated greater adaptability (plant survival rate of 87.8–92.7%), significantly outperforming the Korzar and Snezhka varieties. The combination of the Dalton hybrid’s biological potential, a large seed fraction, and foliar feeding with the Phitospectr preparation resulted in a maximum yield of 4.28 t/ha. Among the varieties, the Snezhka variety was the most productive, with a seed yield increase of 0.31 t/ha under optimal conditions compared to the Korzar variety.