Co‐inoculation of soybean with Bradyrhizobium spp. and Amazonian strains of Trichoderma asperellum and Bacillus amyloliquefaciens increases the productivity and profitability of the crop

Co‐inoculation of soybean with plant growth‐promoting microorganisms has the potential to increase yield, and the Amazon is a biome rich in these beneficial microorganisms. Soybean is the most important grain crop in Brazil and is highly benefited by inoculation with Bradyrhizobium spp. strains, both of which represent exotic symbiotic partners. The objective of this study was to evaluate the effects of soybean co‐inoculation with Amazonian strains of Trichoderma asperellum and Bacillus amyloliquefaciens. Greenhouse and field experiments were conducted during the 2020 and 2021 crop seasons in Brazil, respectively. The experimental design was completely randomized in the greenhouse, and randomized blocks were used in the field, both with 3 × 2 factorial schemes. Standard inoculation with Bradyrhizobium and co‐inoculation with T. asperellum and B. amyloliquefaciens was considered the first factor, and the second factor was represented by phosphate fertilization (0 and 100 kg ha−1 of P2O5). The root system volumes were 25% and 17% higher than those of the standard inoculation with T. asperellum and B. amyloliquefaciens, respectively. In 2020, co‐inoculation with T. asperellum increased yield by 15%, plant height by 27%, and net profit by up to 121 USD compared with standard inoculation. In 2021, co‐inoculation with T. asperellum and B. amyloliquefaciens resulted in increases in several growth parameters compared to those with standard inoculation, including 7% and 13% greater yields, and 159 USD and 309 USD increases in net profit, respectively. Our results indicate the possibility of expanding soybean co‐inoculation with local strains of Bacillus and Trichoderma, with benefits for productivity and profitability. Core Ideas It is possible to expand the co‐inoculation of soybean with other microorganisms. Regionalized strains can benefit soybean productivity and profitability. Amazonian strains in soybean co‐inoculation promote increased root volume.