Co-Inoculation with <i>Bradyrhizobium</i> and Humic Substances Combined with <i>Herbaspirillum seropedicae</i> Promotes Soybean Vegetative Growth and Nodulation
2023
Luciano Pasqualoto Canellas | Rakiely Martins Silva | Lucas José da Silva Barbosa | Fernando Soares Sales | Rafael Chaves Ribeiro | Gabriela Petroceli Mota | Fábio Lopes Olivares
The effect of humic substances (HSs) in combination with or without plant-growth-promoting bacteria on soybean vegetative growth and root nodulation was examined in this study. Seeds were inoculated with <i>Bradyrhizobium japonicum</i> SEMIA 5079 in the presence of HSs from leonardite and <i>Herbaspirillum seropedicae</i> HRC54. Additional HSs and <i>H. seropedicae</i> application at the substrate surface was conducted at the V3 stage. The experiment was carried out in a greenhouse using pots filled with a top layer of an Oxisol soil, and plants were harvested at the R1 stage. The HS and <i>H. seropedicae</i> treatments significantly promoted plant shoot and root growth. The number and weight of soybean nodules were higher in the treated plants when compared to a control. The plant nodulation process was affected by the treatments that included activities of malate dehydrogenase (MDH), nitrate reductase (NR) and plasma membrane H<sup>+</sup>-ATPase (MHA). At low concentrations, the HSs and <i>H. seropedicae</i> increased the nodule quantity, size and weight, favoring plant growth. Combining humic substances and plant-growth-promoting bacteria (PGPB) could be a promising approach to promoting soybean nodulation and increasing crop production.
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