Agronomic efficiency of Optimize 700L containing Bradyrhizobium japonicum in soybean crop (Glycine max L.)

The aim of this study was to evaluate the agronomic efficacy of the Optimize 700L inoculant containing Bradyrhizobium japonicum bacteria (SEMIA 5079 and 5080, 3.0 ×109 CFU mL-1) in seed treatment in soybean crops. In total, 24 field trials were implemented, 12 in the Central-West and 12 in the South of Brazil, during the 2021/2022 harvest. The design was a randomized block design, consisting of five treatments (i - control without inoculation; ii - 200 kg of nitrogen (N200); iii - standard inoculation on the day of planting (IP); iv - Optimize 700L applied 40 days before planting and v - Optimize 700L applied 60 days before planting) and six replicates, replicated in triplicate (different chemical groups). The results obtained showed that the yields observed in the treatments with Optimize 700L ranged from 4.3 to 6.2%. This was statistically superior to that of the Control treatment and equal to that of the standard GlyciMax inoculant applied on the day of sowing. The Optimize 700L inoculant pre-inoculated 40 and 60 days before sowing in soybean crops increased nodulation in the main root and the dry mass of nodules; therefore, it was statistically equal to the commercial standard GlyciMax and superior to the N200 treatment. Additionally, it contributed to nitrogen fixation, chlorophyll content, and shoot and root vigor. Pre-inoculation of the Optimize 700L inoculant 46 to 67 days before sowing, using Bradyrhizobium japonicum strains (SEMIA 5079 and 5080) and specific formulation, combined with protective agents and chemical seed treatments, was as effective as inoculation performed at the time of sowing.