Kokovikhina O. Seed productivity of soybean varieties depending on the elements of cultivation technology under irrigation conditions

Field studies have revealed that the number of irrigations was at its maximum in 2019, ranging from 6 to 9 irrigations during dry conditions, and decreased to 4 to 6 irrigations in the moderately moist year of 2021, with irrigation rates of 3150-4050 and 1800-2700 m3/ha respectively. The cumulative water consumption in the 0-50 cm soil layer was minimal (4114 m3/ha) in 2021 for Ideal variety, whereas for the mid-maturing varieties Oleshshia and Pivdenna krasunia in 2019, it significantly increased to 6463-6487 m3/ha in the 0-200 cm soil layer. Among the components of water consumption, the irrigation rate accounted for the highest proportion (49.2-57.4%), while soil moisture had the lowest share (8.1-16.2%). The lowest water consumption coefficient (1057-1731 m3/t) was observed in Zoria Stepu variety. The application of fertilizers and plant protection resulted in a consistent reduction of the water consumption coefficient for all examined soybean varieties. The highest daily evaporation level, ranging from 82.7 to 85.3 m3/ha/day, was recorded in Pivdenna krasunia and Oleshshia varieties during the second decade of July, while Ideal variety saw a reduction by a factor of 2.3-2.4, down to 36.1 m3/ha/day. The yield of soybean seeds, on average over the years of research, was the maximum, at the level of 4.61-4.75 t/ha, in Oleshshia variety after treating the seeds with Phosphate gel and using biological and chemical plant protection. Variance analysis proved that the varietal composition had the greatest influence on seed yield – 44.1%. The effect of fertilization and plant protection was also very significant – 19.7 and 14.5%, respectively. It was determined that Zoria Stepu and Pivdenna krasunia varieties were superior in terms of stress resistance, and Oleshshia variety was superior in terms of genetic flexibility. A high level of homeostaticity and selection value was demonstrated by the varieties Zoria Stepu, Pivdenna krasunia and Oleshshia, while these indicators were lower by 25.8-150.2% in Ideal variety. The lowest protein content in seeds (30.6%) was found in Ideal variety for growing it without fertilizers and without plant protection. In the variety Pivdenna krasunia, when using Phosphate gel and chemical plant protection, this indicator increased to 35.2%. According to the indicator of conditional protein yield, Oleshshia variety had an advantage due to the treatment of its seeds with Phosphate gel and chemical plant protection, while this indicator increased to 1.75 t/ha, and in Ideal variety without fertilizers and without plant protection, its decrease was recorded by 2.9 times (up to 0.61 t/ha). The maximum content of fat in seeds (21.8%) was in Oleshshia variety, and in Ideal variety it decreased by 17.2 percentage points. The use of fertilizers, as well as compliance with chemical and biological protection of plants contributed to an insignificant increase in fat content. Based on the simulation, it was established that the maximum amount of solar radiation (20.7 MJ/m2 per day) appeared in the dry year of 2019, and in other years it decreased by 5.0-6.7%. The total input of solar energy in 2019 was also the maximum and amounted to 82.9 MJ/m2 per day, and in 2020 and 2021 it decreased by 5.5-6.0%. On average, over the years of research, the highest value of the coefficient of the useful effect of PHAR (2.3%) was recorded in Oleshshia and Pivdenna krasunia varieties. In Zoria Stepu variety, it decreased by 9.5 percentage points, and in Ideal variety – by 35.2. The cost of gross production reached the highest value of 59.4 thousand UAH/ha in the variant with Oleshshia variety when the seeds were treated with Phosphate gel and with chemical plant protection. The maximum cost of 1 ton of soybean seeds, at the level of UAH 6.4 thousand, was formed in Ideal variety. The largest conditional net profit, ranging from 41.4 to 42.4 thousand UAH/ha, was obtained in case with Oleshshia variety with the use of Phosphate gel on the background of biological and chemical plant protection. The level of profitability was the maximum, at the level of 249 to 254%, also for this combination of options. Gross energy gain increased to 59.9 GJ/ha in Oleshshia variety, and in Ideal variety, this indicator decreased by 3.0 times in the control variants of fertilization and plant protection. The minimum coefficient of energy efficiency, at the level of 4.3-4.5, was formed in the varieties Pivdenna krasunia and Oleshshia due to the use of the biological preparation Phosphate gel and the use of chemical plant protection. The maximum energy capacity of 1 ton of soybean seeds (8.4-8.6 GJ) was noted in the variants with the use of nitrogen fertilizer in a dose of N60 against the background of biological plant protection and control.