Agronomic Performance of Microbial Inoculation Strategies in Soybean, Maize and Wheat Across Contrasting Environments

This study evaluated the effects of co-inoculation with Azospirillum brasilense (strains AbV5 and AbV6) and Bradyrhizobium spp. (B. japonicum SEMIA 5079 and B. diazoefficiens SEMIA 5080) on soybean, as well as the response of maize and wheat to A. brasilense inoculation at different nitrogen fertilization levels. Twelve field trials were conducted across four contrasting edaphoclimatic regions during the 2023/2024 growing season using randomized block designs with four replicates. The treatments represented predefined inoculation and nitrogen-management strategies rather than a full factorial design; therefore, the study was intended to compare agronomic management strategies rather than estimate statistical interactions between inoculation and nitrogen fertilization. Co-inoculation in soybean increased the pod number, thousand-grain weight, and grain yield. In maize and wheat, inoculation associated with nitrogen fertilization resulted in significant increases in biomass accumulation and grain yield compared with the uninoculated control. These results indicate that microbial inoculation can improve selected agronomic traits under the field conditions evaluated. In cereals, the association of A. brasilense with different nitrogen fertilization levels improved selected agronomic responses compared with the uninoculated control under the field conditions evaluated, although the magnitude of these responses varied among nitrogen-management strategies and production environments.