RESUMO
The use of microorganisms to improve the availability of nutrients to plants is of great importance to agriculture. This study aimed to evaluate the effect of triple inoculation of cowpea with arbuscular mycorrhizal fungi (AMF), plant growth-promoting bacteria (PGPB) and rhizobia to maximize biological nitrogen fixation (BNF) and promote plant growth. The experiment was conducted in a greenhouse using cowpea plants (Vigna unguiculata L. Walp cv. IPA 206). The treatments included inoculation with strains of Bradyrhizobium sp. (BR 3267 and EI - 6) individually and as a mixture, an absolute control (AC) and mineral nitrogen control (NC), all combined with the presence or absence of native AMF (Glomus etunicatum) and PGPB (Paenibacillus brasilensis - 24) in a 5x2x2 factorial design. All treatments were replicated three times. Contrasts were performed to study the treatment of variables. Inoculation with Bradyrhizobium sp. (BR 3267 and EI - 6) and G. etunicatum favored nitrogen acquisition and phosphorus availability for the cowpea plants. Inoculation with P. brasilensis - 24 increased colonization by Bradyrhizobium sp. and G. etunicatum and promoted cowpea growth, while the nitrogen from symbiosis was sufficient to supply the plants nutritional needs.