Efeitos da co-inoculação de Herbaspirillum seropedicae e Bradyrhizobium japonicum no desenvolvimento agronômico da soja

Abstract

Soybean has a high demand for nitrogen (N) and a strong dependence on biological nitrogen fixation (BNF), carried out mainly by strains of Bradyrhizobium japonicum, which can be enhanced through co-inoculation with other plant growth-promoting bacteria, such as Azospirillum brasilense and Herbaspirillum seropedicae. Co-inoculation has been investigated as a sustainable alternative to improve early plant development, nodulation, and productivity, especially in environments with contrasting soil and climatic conditions. The present study was conducted in two experimental field environments, one located in Londrina, PR, and the other in Rio Verde, GO. Six seed applied treatments were evaluated: a negative control (without any inoculant), one strain of Bradyrhizobium japonicum, an association of Bradyrhizobium japonicum strains with a commercial Azospirillum inoculant (positive control), and three different combinations of Bradyrhizobium japonicum and Herbaspirillum seropedicae, named Bac1, Bac2, and Bac3. The variables measured included grain yield, thousand-grain weight, number of pods, average plant height, average height of the first pod insertion, and average number of nodules. Plant responses to the treatments varied between environments. In Londrina, statistically significant differences were observed for grain yield, number of bags per hectare, thousand-grain weight, first pod insertion height, number of nodes, and number of pods. In Rio Verde, significant differences among treatments were found for grain yield, number of bags per hectare, first pod insertion height, and number of pods, indicating a strong influence of edaphoclimatic conditions on the agronomic performance of the soybean crop. The results reinforce the importance of the interaction between inoculated microorganisms and the environment in soybean development, demonstrating that co-inoculation can be a promising strategy to improve the crop’s productive performance. The study contributes to advancing the understanding of BNF and the role of bacterial combinations in the sustainability of soybean production.