Agronomic efficiency of the Optimize 1000 inoculant containing Bradyrhizobium elkanii bacteria - SEMIA 587 and 5019 - for seed treatment (pre-inoculation) in soybean cultivation

The need to improve agricultural efficiency, with higher yields and lower production costs, is driving current research to identify more efficient management techniques. Among these developing technologies is the inoculation with microorganisms that can promote plant growth, such as biological nitrogen fixation, which in soybeans occurs through symbiosis between the roots and rhizobia. Pre-inoculation (early inoculation) with bacteria of the genus Bradyrhizobium has been evaluated and has provided satisfactory results, making inoculation days before sowing a viable approach. Twelve replicate field trials were conducted in various soil and climate regions across the Midwest and South of Brazil during the 2020/2021 harvest. The randomized block design consisted of 6 treatments [i - control without inoculation; ii - standard inoculation on the day of planting (IP); iii - 200 kg nitrogen (N200), applied 50% at planting and 50% at R1; iv-vi - Optimize 1000 inoculant applied 60, 90, and 120 days before planting (DAP)] and 6 replications, replicated 3 times. The objective was to assess the viability and agronomic efficiency of the Optimize 1000 inoculant containing Bradyrhizobium elkanii bacteria (SEMIA 587 and 5019) in the early treatment of soybean seeds. Treatment with Optimize 1000 between 55 and 143 DAP increased soybean yields by 5.4%, which was significantly more than the standard treatment inoculated on the day of sowing. For the nodulation variables, Optimize 1000 in its longest pre-sowing period (120 days) was statistically equal to the IP treatment. These results suggest that early inoculation of chemically treated seeds with Optimize 1000 and specific protectants can be recommended to improve and optimize soybean production processes when applied up to 143 DAP.