Agronomic Performance of Soybean with Bradyrhizobium Inoculation in Double-Cropped Farming

Land degradation is a serious problem in arid regions, including in Central Asian countries. Soybean symbiosis with rhizobia microbes has an essential role in improving crop productivity and sustaining soil fertility in an arid environment. An experiment was conducted in light straw-colored sierozem soils in the Syrdarya region of Uzbekistan (41.4° N, 64.6° E) under arid conditions over the 2016–2017 and 2017–2018 growing seasons. This study aimed to assess the beneficial N fixation (BNF) ability of soybean in association with the Bradyrhizobium R6 strain and the Bradyrhizobium japonicum USDA110 strains and their combined effect on soil fertility and crop yield. The residues of winter wheat and soybean improved soil structure, i.e., soil humus and N and P contents, significantly differing from those on the soybean followed by summer fallow treatment. Furthermore, soybean in association with dual inoculation had the highest N derived from the atmosphere (Ndfa) (62.9 kg N ha −1 ), followed by individual soybean treatments with the R6 and USDA110 strains at 51.9 and 40.6 kg N ha −1 , respectively. Improved soil quality positively impacted crop output, increasing winter wheat and soybean yields by 36.5% and 34.6%, respectively. Likewise, the yield parameters, i.e., the number of pods, weight of grain per pods, and 1000 seeds were significantly higher in the inoculated treatment with the highest value observed in the dual-inoculated treatment. These results suggest the insertion of soybean with symbiotic bacteria into the cropping system has considerable potential to contribute to sustainable land management practices in arid zones.