The dissertation provides a theoretical generalization of the research results and proposes to scientifically substantiate the solution of the current problem aimed at improving agrotechnological measures for growing winter rapeseed in the conditions of the Northern Steppe of Ukraine. The improvement was achieved by optimizing the sowing dates, seeding rates, nitrogen nutrition system and the use of growth regulators, taking into account the variability of hydrothermal conditions and genotypic features of modern hybrids. The method of work is to increase the yield and stability of seed productivity of winter rapeseed, as well as improve the quality indicators of content and economic efficiency of technology in the zone of risky agriculture.
The dissertation proves that the autumn application of growth regulators in phase 4–5 of true leaf compensation (BBCH 14–15) is an effective agrotechnological method for stabilizing the morphophysiological state of plants and weather stresses.
The studies used generally accepted field and laboratory methods. The results were processed using mathematical statistics methods, in particular, dispersion, correlation and regression analysis, which ensured the reliability of the conclusions obtained.
During the experiment, it was established that the optimal morphobiological parameters and high productivity indicators of winter rapeseed are 0.7 million pcs/ha when sowing 10–20.09 at a rate of 0.7 million pcs/ha. Under such conditions, the temperature of the base for germination is maintained at 14–17 °C, sufficient intensity of growth processes is ensured without overgrowth, a rosette is formed with a high percentage of preservation (84–87%) and a stable potential for spring renewal. An increase in density of more than 0.7 million pcs/ha or too early sowing dates reduced the productivity and economic efficiency of growing the crop.
It is proven that the optimization of nitrogen nutrition within 120–150 kg/ha with distributed application is appropriate for the formation of highly productive and resource-saving agrocenoses: a double application of N150 (N90+N60) provided a yield of 4.17 t/ha versus 2.47 t/ha without nitrogen, increased the protein content to 22.1% and provided the highest economic indicators (conditional net profit of 56.7 thousand UAH/ha, profitability of 152.7%). A greater increase in the nitrogen dose of more than 150 kg/ha did not provide a significant nature of yield or economic benefit.
It is shown that the weather conditions of the autumn period form the limits of the realization of the potential of the crop, determining the initial morphological differences and the subsequent strength of spring recovery. In the arid scenario (IPR 70–75%), plant mass decreased, the height of the growth point increased, and overwintering fell to 58–81%. Growth regulators partially compensated for weather stresses and provided an increase in yield of 0.47–0.65 t/ha; correlation analysis confirmed the predictive value of plant mass in autumn, root collar diameter, and spring recovery index (r up to 0.83), and the regression model explained 87% of the yield variation. Among the genotypes studied, the Temptation hybrid provided the highest stability of productivity under severe stress.
As a result, it was scientifically proven that rational management of the main elements of the technology (sowing dates 10–20.09, seeding rate 0.7 million pcs/ha, optimized nitrogen nutrition 120–150 kg/ha with distributed application and autumn application of growth regulators) ensures increased yield, improved qualitative indicators of growth and increased economic efficiency. growing winter rapeseed in the conditions of the Northern Steppe of Ukraine.
