Effects of Pre-sowing Inoculation of Bradyrhizobium on the Development of Root System and Nodulation of the Soybean (Glycine max L. Merril)

The inoculation of nitrogen fixing bacteria in soybean crop allows to achieve high productivity, reducing or eliminating the nitrogen fertilizers application. Pre-sowing inoculation in the seeds can reduce costs and increase the efficiency of this agricultural practice. The objective of this study was to evaluate the effectiveness of pre-sowing inoculation in the vegetative development and production of soybean. Four field trials were carried out in traditional areas of soybean cultivation in the state of Paraná, Brazil, and the treatments were: standard inoculation with recommended strains carried out on the day of sowing, pre-sowing inoculation at 60, 45 and 30 days before sowing and the control without inoculation. The experimental design was randomized blocks with four replications. Soil fertilization and correction was performed by soil analysis result interpretation and recommendations for the crop. There was no significant difference in the root development of pre-inoculated soybean plants with anticipation of 60, 45 and 30 days before sowing in all the studied areas. Furthermore, all pre-sowing inoculation treatments of the seeds showed nodulation and grain yield similar to the standard inoculation. The control treatment showed nodulation by the native rhizobia of the soil, which a history of soybean production, which provided root system development and grain yield similar to inoculated treatments. We found a positive correlation (p<0.01) between nodulation and root system biomass, that indicate the contributions of nitrogen symbiotic fixation to root system development and leads to high grain yield. Therefore, the pre-sowing inoculation of soybean can be carried out up to 60 days before sowing without prejudice to the development of the soybean root system, nodulation and grain yield.