Efeito da inoculação com Rhizobium tropici (Rhizobiales: Rhizobiaceae) e Azospirillum brasilense (Rhodospirillales: Azospirillaceae), associada à aplicação de cobalto e molibdênio, no desenvolvimento inicial do feijoeiro (phaseolus vulgaris l.)

Abstract

The objective of this study was to evaluate the effects of inoculation with Rhizobium tropici and Azospirillum brasilense, alone or in co-inoculation, with and without the application of the micronutrients Co and Mo, on the initial development of common bean (Phaseolus vulgaris L.) cultivar BRS FS311 grown in pots. The experiment was conducted in a completely randomized design with seven treatments and four replications, using sandy soil with low fertility, especially deficient in phosphorus and with low CEC, conditions limiting Biological Nitrogen Fixation (BNF). Evaluations were carried out at the V5 stage, considering the number of nodules, height, stem diameter, and whole-plant dry mass. There was a total absence of nodules in all inoculated treatments, indicating that the chemical and physical characteristics of the soil prevented the symbiosis with R. tropici and the associative effect of A. brasilense. Thus, inoculation did not promote increases in the evaluated parameters. Treatment T1, which received mineral fertilization with NPK, showed the greatest growth, demonstrating that, in the absence of BNF, mineral nitrogen was decisive for plant development. The high coefficients of variation reflected the heterogeneity of the plants and the nutritional limitations of the soil. It is concluded that, under conditions of low fertility and absence of available phosphorus, BNF is not established, making the effects of inoculation unfeasible. The necessity of soil correction for the technology to present an agronomic response is emphasized.