The use of liquid and peaty inoculants containing Bradyrhizobium japonicum strains to supply nitrogen to soybean has already been consolidated. However, in recent years, the co-inoculation technology has been used, where, besides the inoculum based on B. japonicum, strains of diazotrophic bacteria of the genus Azospirillum brasilense have been inoculated, which has been proven to be effective in grasses of great economic importance like corn and wheat. This technology has resulted in advantages for soybean crop, with research reporting root system enlargement and consequently increase in number and mass of nodules, greater biological nitrogen fixation and higher plant development and productivity. In this context, the present study refers to the results obtained in four experiments carried out in the 2016/2017 crop, in four different locations: Toledo-PR, Palotina-PR, São Miguel do Iguaçu-PR and Cascavel-PR. The objective of the present study was to evaluate the agronomic efficiency of Bradyrhizobium japonicum (strain 5079 and 5080) and Azospirillum brasilense (strain Ab-V5 and Ab-V6) inoculants in four distinct regions. The inoculant was developed by the company Nitro 1000 - Biological Inoculants and the tests were performed to meet the requirements of the Ministry of Agriculture, Livestock and Supply regarding the registration of the product. The experiments were conducted in a randomized block design with seven treatments and four replications, totaling 28 plots each. MONSOY M 6410 soybean cultivar was used in all four experiments. The treatments were: T1 - Control (absence of nitrogen fertilization and inoculation); T2 - Control with nitrogen fertilization - 200 kg ha-1 of N (50% available at sowing and 50% of N at flowering stage), and no inoculation; T3 - Inoculation with GRAP NOD L® standard liquid inoculant containing B. japonicum (SEMIA 5079 and SEMIA 5080) at a dose of 100 mL 50 kg-1 seeds; T4 - Inoculation with standard liquid inoculum GRAP NOD A® containing A. brasilense (AbV5 and AbV6) at a dose of 100 mL 50 kg-1 seeds; T5 - Inoculation with GRAP NOD L® standard liquid inoculum containing B. japonicum (SEMIA 5079 and SEMIA 5080) at a dose of 100 mL 50 kg-1 + Inoculation of GRAP NOD A® standard liquid inoculum containing A. brasilense (AbV5 and AbV6) at the dose of 100 mL 50 kg-1 seeds; T6 - Inoculation with NITRO 1000 liquid inoculant containing B. japonicum (5079 and 5080) at a dose of 100 mL 50 kg-1 seeds + NITRO 1000 liquid inoculant containing A. brasilense (AbV5 and AbV6) at a dose of 100 mL 50 kg -1 of seeds; and T7 - Inoculation with NITRO 1000 peat inoculum containing B. japonicum (5079 and 5080) at a dose of 100 g 50 kg-1 seeds + NITRO 1000 peat inoculum containing A. brasilense (AbV5 and AbV6) at a dose of 100 g 50 kg -1 of seeds. At stage R1, plant collections were performed to measure morphobiometric variables. Root dry mass, number of nodules per plant, nodule dry mass, plant height, stem diameter, total shoot dry mass and leaf nitrogen content were determined. At stage R9, soybean crop yield and grain N content were evaluated. The results showed that in all evaluated sites the use of co-inoculation with B. japonicum + A. brasilense increased soybean crop development as well as yield. Thus, the co-inoculation of soybean seeds with Bradyrhizobium japonicum-based inoculants (strains 5079 and 5080) and Azospirillum brasilense (strains AbV5 and AbV6), in the liquid and peat formulations in their respective doses, are agronomically efficient to improve the yield. crop development and increase soybean crop productivity, contributing to sustainability in agriculture.

Keywords: Glycine max L., diazotrophic bacteria, biological nitrogen fixation, seed inoculation, productivity.