Co-inoculação de rizóbio e bactérias promotoras de crescimento vegetal em feijoeiro comum

Abstract

The objective of this work was to evaluate the production of biomass and grains in common bean (Phaseolus vulgaris) in co-inoculation with rhizobia and plant growth promoting bacteria. The work was divided into three chapters. The first evaluated the compatibility between rhizobia and plant growth promoting bacteria and their effects on plant growth. In Petri dishes assay, Azospirillum amazonense and A. brasilense were co-inoculated with Rhizobium tropici at three application levels, and no antagonism was detected. The experiment in Leonard jars had a 5x3+3 factorial with eight replications, consisting of five bacteria (Bradyrhizobium diazoefficiens, B. elkanii, A. amazonense, Azospirillum brasilense and Escherichia coli) and three application levels (104, 106 and 108 CFU mL-1), all co-inoculated with R. tropici plus three additional treatments (control, nitrogen, and inoculated with R. tropici). Co-inoculation increased nodulation, N concentration and content in the shoot. The experiment in pots with soil had 3x2x2+4 factorial with four replications, consisting of three growth promoters (B. diazoefficiens, B. elkanii and A. brasilense), two application levels (104 and 106 CFU mL-1), two N sources (R. tropici and mineral N), and four additional control treatments (absolute control, nitrogen, inoculated with rhizobia and co-inoculated with AZOTOTAL®). Inoculation with A. brasilense associated with N fertilization increased the production of leaves and shoots. The second chapter aimed to evaluate the growth and production of common bean under co-inoculation. An experiment in pots with soil in a factorial 2x3+4 with 8 repetitions were performed by combining the inoculation of R. tropici with A. brasilense or B. diazoefficiens in three application levels (104, 106 and 108 CFU mL-1) plus the control treatments (absolute, nitrogen, inoculated with rhizobia and co-inoculated with AZOTOTAL®). Four replications were harvested at 45 days after sowing, and four at grain maturity. Co-inoculated plants showed shoot mass, number of pods, shoot N content, grain yield, number of seeds and pods per plant higher than the control inoculated with rhizobia. The leaf chlorophyll Falker index was similar in co-inoculated treatments and under mineral N fertilization, but lower than the exclusive inoculation R. tropici. In the third chapter it was evaluated the growth and production of common bean under different strategies of mineral N fertilization associated with co-inoculation with R. tropici and A. brasilense. The experiment had seven treatments with four replications: control; inoculation with R. tropici without N application; control with mineral N; co-inoculation with R. tropici and A. brasilense without N fertilization or application of 20 kg ha-1 of N at sowing; inoculation with R. tropici and 20 kg ha-1 of N at sowing; inoculation with A. brasilense and 20 kg ha-1 of N at sowing. Plants were harvested at 45 days after sowing and at grain maturity. Co-inoculation combined with the N fertilization resulted in higher mass values of leaves, stem, shoot, dry mass of grains, number of grains per plant and accumulation of N in pods and grains.