Morphological peculiarities of soybean as affected by application of micronutrients and plant growth regulators

Purpose. Determining the morphological features of soybean varieties ‘Ustia’, ‘Cordoba’, and ‘Estafeta’ under the effects of micronutrients and growth regulators. Methods. The research was carried out in 2020–2022 at the Verkhniachka Experimental Breeding Station of the Institute of Bioenergy Crops and Sugar Beet, in the zone of unstable moisture in the Right-Bank Forest-Steppe of Ukraine. The field experiment was laid out according to the following design: factor A – soybean varieties (‘Aratta’, ‘Cordoba’, and ‘Feieria’); factor B – micronutrients [without micronutrient; Yara Vita Mono Molitrak at the budding stage (0.25 l/ha); Yara Vita Mono Molitrak at the budding stage (0.25 l/ha) + Yara Vita Mono Molitrak at the flowering stage (0.25 l/ha)]; factor C – growth regulators (without growth regulator; Biosyl; Radostym). Results. The most effective for increasing plant height was the use of growth regulators Biosyl and Radostym, especially in combination with the micronutrient Yara Vita Mono Molitrak at the budding stage. In particular, in the ‘Aratta’ variety, this indicator exceeded the control by 11.7 cm (with application of Biosyl), by 10.4 cm (Radostym) ‘Cordoba’, and by 9.5 cm (Biosyl) in ‘Feieria’. The maximum increases were recorded with the application of Yara Vita Mono Molitrak together with Radostym at the budding and flowering stages, accounting for 17.7,11.5, and 12.9 cm respectively. The combined application of micronutrients with growth regulators also significantly increased the number of inflorescences per plant. In particular, in the ‘Aratta’ variety, with single or double application of Yara Vita Mono Molitrak in combination with Radostym, the number of inflorescences increased by 3.1 and 3.0, respectively compared to the control. The application of Radostym was also effective for other soybean varieties. Conclusions. Treatment of soybean plants with the micronutrient Yara Vita Mono Molitrak at the budding stage, as well as the consequent application of this product at the budding and flowering stages along with the growth regulator Radostym, contributed to the increase in the number of pods in the ‘Aratta’ variety by 2.8 and 3.0, respectively. Similar effectiveness of Radostym was observed in other varieties. In the ‘Aratta’ variety, the use of Yara Vita Mono Molitrak at the budding stage alone contributed to an increase in the number of seeds per plant by 1.6, and by 1.5 in combination with Radostym. In the ‘Cordoba’ variety, consequent application of the micronutrient in combination with Radostym resulted in an increase of 0.8 seeds per plant. In the ‘Feieria’ variety, the best result of 1.2 seeds per plant was obtained by combining the micronutrient with Biosyl. Application of Yara Vita Mono Molitrak at the budding stage together with the growth regulator Radostym or in two stages (budding and flowering) with Biosyl contributed to the increase in individual plant productivity. In particular, in the ‘Aratta’ variety, this increase compared to the control was 0.34 and 0.20 g respectively.