The interaction of cowpea with atmospheric N fixing bacteria can increase productivity and reduce production costs. In this study, it was evaluated in the field, the agronomic efficiency, through the accumulation of biomass of shoot, root, number and biomass of nodules, relative efficiency and productivity of three cultivars of cowpea (BRS New Era, BRS vibrant and Vinegar), in independent experiments, inoculated with five strains of rhizobia, BR 3302 (UFLA 3-84), BR 3301 (INPA 03-11B), BR 3262, BR 3299 and BR 3267, two controls, control and fertilized with nitrogen (50 kg of N ha-1) for each experiment, in blocks. For each cultivar the response of each strain inoculated varied within traits. However, strain BR 3302 showed a constant on the characteristics of biomass and productivity assessed, to cultivar Nova Era in Experiment 1, with values near the fertilized soil. For the cultivars Pujante and Vinagre, in experiments 2 and 3, respectively, were also observed satisfactory results with the inoculation of strain BR 3302, with productivity about 22 and 11% higher than the treatment fertilized with nitrogen in each experiment, however, did not differ on the other strains inoculated. The mean of three independent experiments, were observed grain yields of cowpea of 743 and 826 kg ha-1 for the treatments with nitrogen and the treatment inoculated with strain BR 3302, respectively. Thus, strain BR 3302 provided the best results for the three cultivars of cowpea.
Vigna unguiculata; Biological nitrogen fixation; Soil biology
