Does inoculation of multifunctional microbial consortia contribute to compelling increases in soybean yields?

Abstract Aims : Inoculating multifunctional microbial consortia offers potential benefits for enhancing plant growth and grain yield formation. This study verified the feasibility of inoculating soybean ( Glycine max ) seeds with multifunctional microbial consortia to improve soybean productivity. Methods : Seeds were inoculated with twelve combinations of inoculants [(1) Bradyrhizobium japonicum and B . diazoefficiens for biological N 2 fixation, (2) Azospirillum brasilense for growth promotion via phytohormone release, (3) Bacillus megaterium (= Priestia megaterium ) and B. subtilis for enhancing P uptake, and (4) Trichoderma harzianum as biopesticide] and grown in chamber, greenhouse, and field experiments. In the chamber, inoculated seeds were submitted to germination tests. In the greenhouse, inoculated seeds were sown in pots with non-sterile soil, and plant growth was monitored until the flowering stage. In the field, plants were cultivated until physiological maturity. Soil and plant samples were collected at three growth stages: vegetative (V4), reproductive (R1), and maturation. Measurements included shoot, root, nodules, grain masses, and grain yield, alongside analyses of seed N, P, lipid, protein, and carbohydrate contents. Results : Excessive number of microbial inputs and the inclusion of T. harzianum in the microbial consortia impeded seed germination, hindered initial vegetative growth, and decreased plant densities in the plots. Nevertheless, plants may have adjusted because these treatments did not significantly impact grain yield; intriguingly, they even elevated soybean grain lipid content. Conclusions : Inoculating multifunctional microbial consortia holds promise as a sustainable approach in agriculture. Still, care should be taken concerning an excessive number and compatibility of microorganisms composing the consortia.