The formation of photosynthetic indicators of soybean varieties depending on the nutrition area in the Right Bank Forest Steppe of Ukraine

Abstract

Purpose. To determine the influence of row width and seeding rate on the formation of soybean photosynthetic indicators. Methods. The research was carried out in 2021–2023 in the stationary crop rotation of the Plant Breeding Department in the fields of the Agronomic Research Station of the National University of Life and Environmental Sciences of Ukraine (Pshenychne, Vasylkiv district, Kyiv region). Scheme of the experiment: factor A – sowing method: ordinary row with a row spacing of 19 cm; strip with a row spacing of 19 cm + 38 cm + 19 cm; wide-row with a row spacing of 38 cm; factor B – seeding rate: 450, 600 and 750 thousand seeds/ha. Results. Thickening of crops contributed to an increase in the number of leaves on soybean plants as a result of increased competition for nutrients and solar energy. At the seeding rate of 450,000 seeds/ha, the number of leaves on one plant of the ‘Sirelia’ variety was on average 50.8, ‘Saidina’ 52.4, ‘Vyshyvanka’ 51.7, and ‘Zhaklin’ – 54.6. With an increase in the seeding rate to 600,000 seeds per hectare, this indicator increased by 2.9 leaves in ‘Sirelia’, by 1.3 in ‘Saidina’, by 1.1 in ‘Vyshyvanka’, and by 2.1 in ‘Zhaklin’. Siimilar regularities were observed in the case of a further increase in the seeding rate to 750,000 seeds/ha: 4.1; 2.6; 1.9 and 3.7 leaves per plant, respectively. Therefore, when growing soybean in thickened stands, leaf area increases as the number of plants per unit area of the field increases. After all, competition is intensifying and plants are trying to reach more efficient assimilation of solar energy. In particular, in the phase of bean formation in the ‘Sirelia’ variety, the highest values of the leaf area were obtained when growing plants at a planting design of 19 cm + 38 cm + 19 cm and a seeding rate of 750,000 seeds/ha – 46.5 thousand m2/ha. Accordingly, in second place in terms of the formation of the leaf area was planting design 38 cm + 38 cm + 38 cm and the seeding rate of 750,000 seeds/ha – 45.1 thousand m2/ha. The variety ‘Saidina’ when grown at a planting design of 38 cm + 38 cm + 38 cm and a seeding rate of 750,000 seeds/ha of seeds had a leaf area of 45.5 thousand m2/ha, ‘Vyshyvanka’ 46.6 thousand m2/ha, and ‘Zhaklin’ 48.5 thousand m2/ha, that is, these indicators were the maximum for these varieties. Conclusions. On average, the yield of dry matter in ‘Sirelia’ and ‘Saidina’ was 3.21 t/ha, in ‘Vyshyvanka’ 3.00 t/ha, and in ‘Zhaklin’ 3.09 t/ha. In ‘Sirelia’, at the row widths of 19 cm + 38 cm + 19 cm and a rate of 600,000 seeeds/ha, dry matter yield of 3.53 t/ha was obtained, and the maximum was recorded for the same row width and seeding rate of 750,000 seeds/ha – 3.57 t/ha. The obtained indicator was the largest among all studied varieties. The highest rates of net photosynthesis productivity (NPP) at the time of flowering in the ‘Sirelia’ variety were at the planting design of 19 cm + 38 cm + 19 cm and the seeding rate of 450,000 seeds/ha – 1.08 g/m2 of dry matter per day, in ‘Saidina’ 1,02, and in ‘Zhaklin’ 1.06 g/m2. At the same time, in ‘Vyshyvanka’ at a planting design of 19 cm + 38 cm + 19 cm and a seeding rate of 600,000 seeds/ha, the NPP was 0.94 g/m2 of dry matter per day. At the time of formation of beans, the highest dry matter was formed by the variety ‘Sirelia’ at a row width of 19 cm + 38 cm + 19 cm and a seeding rate of 600,000 seeds/ha – 0.65, and ‘Vyshyvanka’ – 1.24 g/m2 per day. In the varieties ‘Saidina’ and ‘Zhaklin’, of dry matter was at a planting design of 19 cm + 38 cm + 19 cm and seeding rate 450,000 seeds/ha: 1.17 and 1.40 g/m2 per day of dry matter, respectively.