Effects of soybean co-inoculation with plant growth promoting rhizobacteria in field trial

The aim of this study was to investigate the possibility of improving the microbiological fertilizer for soybean by co-inoculation with PGPR strains. Experiment was carried out under field conditions, on a chernozem soil, using soybean cultivar Galina and five inoculation treatments: B. japonicum; B. japonicum + A. chroococcum + humic acid; B. japonicum + A. chroococcum; B. japonicum + B. subtilis; B. japonicum + B. megaterium. Bacterial treatments had a positive effect on activity and number of investigated microbial groups in rhizosphere, nitrogen fixation parameters and yield of soybean. Inoculation, on average, increased the number of azotobacters, total microbial number, ammonifiers, N-fixing bacteria, actinomycetes, dehydrogenase activity, as well as the mass and number of nodules, nitrogen content in plants and seeds, number of poods and seeds, dry seed mass, and yield of soybean. Co-inoculation had a better effect on the number of microorganisms, dehydrogenase activity and yield of soybean, while the best effect on nitrogen fixation and yield parameters was achieved by single inoculation.