English

Abstract

Bioinoculants are widely used in Brazil, based on efficient and low-cost. This study aimed to evaluate the agronomic efficiency of co-inoculation with Bradyrhizobium species and Azospirillum brasilense in soybean seeds. Field trials were established in four regions of Brazil using a randomized block design  with 8 treatments and 4 replications as follows: T1 - Control, T2 - 200 kg ha-1 N, T3 - Bradyrhizobium spp. – peat; T4 - Bradyrhizobium spp. - liquid, T5 – A. brasilense, T6 - Standard co-inoculation Bradyrhizobium spp. + A. brasilense, T7 - Co-inoculation ratios: 1:1 Bradyrhizobium ssp. GRAP NOD L®  + A. brasilense GRAP NOD AL®, T8 - Co-inoculation ratios: 1:1.5 Bradyrhizobium ssp. GRAP NOD L® + A. brasilense GRAP NOD AL®. The study results demonstrated the influence of co-inoculation 1:1.5, providing increments in shoots and root dry mass, nodules number and dry mass, pods number per plant, and yield when compared with the control and conventional N fertilization. The co-inoculation in the ratios 1:1 and 1:1.5, positively influenced the soybean development. These results confirmed that potential of the co-inoculation in incrementing soybean yield, which justify the recommendation of these treatments to reduce mineral N fertilization, improving good agronomic practices. Key words: Rhizobia, Glycine max, BNF, PGPB, inoculation, plant nutrition, crop yield, plant-bacteria symbiosis, nitrogen fertilizer.