Economic Assessment of Rhizobium tropici and Azospirillum brasilense Co-Inoculation in Common Bean

The common bean cropping system has a high cost, mainly due to using nitrogen fertilisers. An alternative for a replacement to reduce production costs is the co-inoculation technique of Rhizobium tropici and Azospirillum brasilense. This study aimed to evaluate the economic viability of co-inoculation of common beans via sowing furrow. Data from five field experiments conducted in three locations in three seasons were used. The treatments consisted of absolute control (without inoculation and fertilisation), nitrogen fertilisation, simple inoculation with R. tropici and co-inoculation with R. tropici and different doses of A. brasilense applied in the sowing furrow. The economic analysis was carried out based on market prices and indexes, depending on the grain production of the different treatments. Treatment with nitrogen fertiliser (80 kg ha⁻¹ of N) resulted in higher production costs, with an average value of USD 1,889 ha⁻¹. Co-inoculation with two doses of R. tropici and four doses of A. brasilense provided the highest mean gross revenue values, net income and benefit-cost-ratio. Co-inoculation with two doses of R. tropici and four doses of A. brasilense resulted in a benefit-cost-ratio of 8 to 11% greater than simple inoculation with Rhizobium tropici, nitrogen treatment and commercial inoculant. Co-inoculation with R. tropici and A. brasilense, in addition to providing high yields, also provides high profitability, proving to be a technology that can contribute to the reduction/replacement of the use of nitrogen fertilisers and reduction of environmental impacts without compromising yield and profitability of common beans.