Enhancing soybean adaptive potential and productivity with endophyte-rhizobial inoculation

The research aim was to investigate the effect of pre-sowing complex inoculation with endophytic and nodule bacteria on the rhizosphere microbiocenosis, soil macronutrient content, adaptive potential and productivity of soybean under the influence of stressful weather and climatic factors. A split-plots design was used to conduct a two-factor field experiment with soybean varieties of different maturity groups: the ultra-early maturing ‘Diona’ and the medium-early maturing ‘Sviatohor’. Microbiological methods were used to obtain inoculants based on nodule and endophytic bacteria (Bradyrhizobium japonicum as part of the complex bioformulation RyzobinK) and their mixtures with endophytic bacteria (Bacillus velezensis IMV B-8134, B-8135, Pseudomonas sp. 6), as well as to determine the abundance of microorganisms from various ecological-functional groups by inoculating soil suspensions onto selective agar media. Agrochemical methods were used to determine soil macronutrients, and statistical methods were applied for data analysis. The stimulatory and stress-protective effects of co-inoculation of seeds with nodule and endophytic bacteria on microbial communities in the rhizosphere soil, as well as on the development and yield of various soybean varieties on irrigated lands in southern Ukraine, have been demonstrated. An increase in the number of microorganisms belonging to the main ecological- functional groups and in the content of available forms of nitrogen, phosphorus and potassium in the rhizosphere soil was established. The most effective treatment in terms of synergistic action on soybean was found to be the treatment of seeds with RyzobinK in combination with Bacillus velezensis IMB B-8134. The average yield for the ‘Diona’ variety was 2.69 t/ha and for the ‘Sviatohor’ variety – 2.95 t/ha, which exceeded the control values by 38-40%. Practical value lies in effective pre-sowing endophyte-rhizobial co-inoculation of soybean seeds, improving productivity and stability of agrophytocenoses under climate change