Synergistic Effect of PGPR and Nutrient Complex on Soybean Seed Germination and Initial Seedling Growth

Biostimulants based on Bradyrhizobium japonicum are commonly used in soybean production. However, the effect of nitrogen-fixing bacteria in consortia with other plant growth-promoting rhizobacteria (PGPR) and their integration with mineral nutrients on soybean seed quality has not been explored. The study aimed to examine the effects of five treatments on seed germination and initial seedling growth of two soybean cultivars (‘NS Apolo’, ‘NS Rubin’): control (untreated seeds); Br. japonicum (BJ), BJ and nutrient complex (NC), BJ, Azotobacter chroococcum (AC), Bacillus subtilis (BS), and NC; BJ, AC, Bacillus megaterium (BM), and NC. Seed treatments significantly enhanced germination energy, seedling vigor index, root length, fresh shoot weight, fresh root weight, dry shoot weight, and dry root weight of both cultivars, as well as final germination, shoot length, and shoot elongation rate of ‘NS Rubin’, as compared to the control. The highest effect on the investigated parameters was achieved by integrated use of PGPR and nutrients (BJ + BM + AC + NC), indicating that integration of PGPR with a targeted NC represents an innovative approach with practical implications for improving early soybean establishment and field performance.