Desempenho do feijoeiro comum sob inoculação conjunta de bactérias promotoras de crescimento vegetal e estirpes de Rhizobium

Abstract

Co-inoculation of plant growth promoting bacteria emerged as a technique for improving development and crop productivity due to the synergistic effect of these bacteria. The objective of this work was to evaluated the responses in terms of nodulation, biomass production and grain yield, of co-inoculation of plant growth promoting bacteria associated with Rhizobium sp. strains already established for common bean (Phaseolus vulgaris L.) crop. Two greenhouse experiments and three field experiments were carried out. The greenhouse experiments aimed to evaluate the effect of co-inoculation of Rhizobium sp. and growth promoting bacteria in the initial stages of vegetative development of two common bean cultivars. The experiments had completely randomized design with four treatments and six replications, and were harvested at the phenological phases V3 and V4 (first and third trifoliate leaf fully expanded, respectively), with the cultivars Pérola and BRS Esteio. The coinoculation of Rhizobium with Bradyrhizobium elkanii stimulated the nodulation, in both stages for cultivar Pérola and in V4 for cultivar Esteio. Co-inoculation with Bradyrhizobium elkanii also stimulated the initial vegetative growth, more intensively at V4, with increases of 67% and 28% in the shoot mass for Pérola and Esteio, respectively. There was no difference between co-inoculation with growth promoters and Rhizobium sp., as compared to sole inoculation with Rhizobium for root dry mass. Field experiments evaluated the effect of coinoculation of growth promoting bacteria associated with Rhizobium strains in the production of biomass and grain yield in three different agroecological conditions. Two experiments were conducted in Macaé - RJ, Brazil, in areas with and without previous cultivation of common bean and distinct soil physicochemical characteristics, with the BRS Esteio cultivar, in a randomized block design with five replicates and five treatments: absolute control, nitrogen control (80 kg ha-1 N), inoculation with commercial strains of Rhizobium, Rhizobium and A. brasilense co-inoculation, and Rhizobium and B. elkanii co-inoculation. In the experiment conducted at Embrapa Agrobiologia, a treatment with a co-inoculation with A. brasilense and application of mineral N in cover (40 kg ha-1 of N) was added, all treatments evaluated with the cultivars BRS Esteio and Ouro Negro. The plants were sampled at full bloom and grain maturation. In the field conditions, the growth promoting effect of the co-inoculation technology was not confirmed in terms of biomass production and grain yield of common bean crop.