Effect of pre-sowing treatment of soybean seeds with biopreparations on the photosynthetic pigments content and yield under unstable moisture conditions and organic farming

Global soybean production is continuously increasing, as it remains one of the most in-demand crops on the global food market. At the same time, climate changes, manifested through rising temperatures and precipitation deficits during the crop's vegetative period, significantly affects its yield. This necessitates the implementation of new technological solutions that ensure the efficient use of production resources and the safety of the final product. One of such promising methods is the pre-sowing treatment of soybean seeds with biopreparations, which enhance plant resistance to stress factors and contribute to achieving potential yields with high quality. The aim of this study is to determine the effect of presowing inoculation and treatment with a phytohormonal preparation on the content of photosynthetic pigments and yield of soybeans in organic farming system in challenging climate conditions. Field experiments conducted in 2022–2024 in Poltava region investigated the effect of pre-sowing seed treatment of the «Horol» soybean variety with the inoculant Legume Fix and the phytohormonal preparation «Violar» on leaf area, photosynthetic pigment content, and yield under various weather conditions within an organic farming system. The results showed that pre-sowing seed treatment contributed to an increase in leaf area by an average of 13.4 % with «Legume Fix» and 19.3 % with «Violar». It was established that treatment with «Violar» led to an increase in the concentration of Chl a, Chl b, and total Chl (a+b) compared to the control by an average of 18.9 %, 13.3 %, and 17.2 % respectively, whereas inoculation with «Legume Fix» increased these indicators by 7.4 %, 3.4 %, and 6.2 % respectively. It was also determined that pre-sowing seed treatment with «Legume Fix» and «Violar» resulted in an average yield increase of 13.2 % and 20.6 % respectively, compared to the control plants. A strong direct correlation was calculated between leaf area, Chl (a+b) content, and yield levels across all study variants: control (0.990; 0.986), «Legume Fix» (0.996; 0.983), and «Violar» (0.986; 0.988) respectively. Key words: Glycine max L. Merr., organic farming, inoculation, leaf area, photosynthetic pigments, weather conditions.