Dynamics of formation of air-dry mass of sunflower hybrids of different ripeness groups under the influence of pre-sowing seed treatment and foliar fertilization in the conditions of the North-Eastern Steppe of Ukraine

The article presents the research results on the influence of pre-sowing seed treatment and foliar fertilization on the formation of air-dry mass of sunflower hybrids of different ripeness groups in the North-Eastern Steppe of Ukraine. The research was conducted in 2023, 2024 on the basis of the farm «AGRO-2011» in Blyzniukivskyi district of Kharkiv region. A two-factor field experiment was set up using the split-plot method in three replications. The first-order plots included three sunflower hybrids, the second-order plots included ten variants of pre-sowing seed treatment and foliar feeding with different combinations of growth stimulants and complex microfertilizers. The area of the sowing plot was 112.0 m2 , and the area of the accounting plot was 73.5 m2 . Analysis of the obtained results revealed a significant impact of joint application of growth stimulants and microfertilizers on the formation of higher air-dry mass of sunflower. At the pre-sowing seeds treatment with the germination stimulator «Humifield Forte» and three foliar feedings with a mixture based on growth stimulants «Regoplant» and «Fulvital plus» with the microfertilizer «LF-Sunflower», a significantly higher air-dry mass of sunflower plants was observed in all phases. In the phase of full seed ripeness in hybrids «Si Chester», «Concord» and «Terrasol» in this variant, it averaged 671.3, 684.0 and 671.9 g/m2 , which is 11.2, 8.8 and 9.4% more than in the control. High rates of air-dry mass of plants of all sunflower hybrids were also noted in the variant where two foliar feeding with a mixture based on «Regoplant», «Fulvital Plus» and microfertilizer «LF-sunflower» was carried out. In this variant, the air-dry weight of plants was also significantly higher than in the control one, and at the same time it did not differ statistically from the variant where three foliar applications with a similar mixture were carried out. Therefore, taking into account the additional costs of the third feeding, it was not reasonable in terms of the formation of air-dry mass of plants. Key words: sunflower, hybrids, growth stimulants, microfertilizers, air-dry mass, pre-sowing seed treatment, foliar feeding.