Bradyrhizobium and Azospirillum co-inoculation associated with cobalt and molybdenum application in the soybean crop

Co-inoculation between bacteria of the genera Bradyrhizobium and Azospirillum can enhance the nodulation and promote the development of the soybean [Glycine max (L.) Merrill] root system, contributing to the increase in grain yield, in addition to the reduction in production costs and contamination of natural resources. Cobalt (Co) and molybdenum (Mo) use can also favor biological nitrogen fixation. The research evaluated the co-inoculation effect of bacteria associated with the Co and Mo application in soybean crop. The randomized blocks design was employed, in a 2 x 6 factorial scheme, presence and absence of Co and Mo and five ways of using the products Bradyrhizobium and Azospirillum, plus control, with four replications. The treatments were formed by the control (not inoculated + 20 kg N ha(-1)); seed inoculation with Bradyrhizobium (100 mL ha(-1)) + 20 kg N ha(-1); seed inoculation with Bradyrhizobium (100 mL ha(-1)) and three treatments applying Bradyrhizobium + Azospirillum in furrow, in different doses. Height of insertion of the first pod, total number of pods and grains per plant, weight of 100 grains and grain yield were evaluated. Inoculation of Bradyrhizobium japonicum associated with co-inoculation of Azospirillum brasilense via foliar and Co and Mo, provided increases in the number of pods per plant, number of grains per pod and weight of 100 grains, reflecting increases in grain yield. The use of Co and Mo, on average, increased soybean yield by 10%, resulting in an average yield of 4,904 kg ha(-1).