In conclusion, our results have verified the important effects of co-inoculation with rhizobia and AM fungi on common bean growth and the synergistic relationship between rhizobia and AM fungi. These results show an interesting practical application for agricultural development in marginal lands that are often deficient in P. The symbiosis with rhizobia and mycorrhiza under P limitation is a biological technology that may improve symbiotic nitrogen fixation in leguminous plants for an agricultural development that would be friendly to the environment and the consumers.