Soybean growing under inoculation by Bradyrhizobium japonicum strains in the Forest-steppe and Steppe zones of Ukraine

The strategic task of soybean ( Glycine max (L.) Merr.) breeding today is to create highly adaptive cultivars that have a high level of genetic protection from biotic and abiotic environmental factors and are able to maximise the yield potential in combination with a high grain quality. The use of inoculants is an environmentally safe measure that can significantly increase the soybean yield and reduce the level of plant damage by pests. The aim of the experiment was to evaluate the biological inoculants based on Bradyrhizobium japonicum strains under different cultivation conditions and dry-resistant soybean cultivars ‘Almaz’ and ‘Antracite’. B. japonicum strains 634b for the ‘Almaz’ were the most effective in the Forest-steppe, as the yield increased by 0.11 t ha -1 compared to that of the control treatment. At the same time, the yield increased by 0.05 t ha -1 due to the application of B. japonicum strains М8. Under these cultivation conditions, for the ‘Antracite’, the B. japonicum strains М8 provided the greatest growth of yield (increased by 0.23 t ha -1 compared to that of the control) and by 0.14 t ha -1 when the B. japonicum strains 634b were used. On the average, over the experimental years, soybean cultivars in the Forest- steppe had a much higher yield (2.70–2.88 t ha -1 ) compared to that of the Steppe (1.28–1.88 t ha -1 ). Treatment with the B. japonicum strains 634b significantly increased the yield for the ‘Almaz’ and ‘Antracite’ in the Steppe. In the Forest-steppe, the treatment with B. japonicum strains 634b was more effective for the ‘Almaz’ and the one with B. japonicum strains М8 for the ‘Antracite’. Quantitative symbiotic indices of soybeans were higher in the treatment with B. japonicum strains 634b for the ‘Almaz’ in the Forest-steppe and Steppe. In the Steppe, the application of B. japonicum strains М8 was more effective for the ‘Antracite’.