ECONOMIA DA FIXAÇÃO BIOLÓGICA DE NITROGÊNIO EM ESPÉCIES DE FEIJÃO COMUM, CAUPI E MUNGO NO BRASIL

Abstract

Biological nitrogen fixation (BNF) is a key factor in ensuring the sustainability of agricultural production and food security. This study aimed to estimate the economic savings generated by BNF in common bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), and mung bean (Vigna radiata) production systems. Data on crop area, production, and productivity were obtained from the Brazilian Agricultural Censuses of 2006 and 2017. We estimated the amount of N (as urea) required to produce 1,000 kg of grain for each bean species in the absence of inoculation. The contribution of BNF to the N supply of each legume species was obtained from studies using the 15N natural abundance method. The economic benefits generated by BNF reached US$ 6 million for mung bean, US$ 59 million for cowpea, and US$ 119 million for common bean in 2017. The savings generated by BNF per hectare cultivated with common bean increased by 40% in 2017 compared with 2006, mainly due to the significant 64% increase in grain yield of this crop. Between 2006 and 2017, BNF maintained common bean as the main CO₂e-mitigating species, with stable values around 1.2 million tCO₂e. In contrast, cowpea showed a marked decline, from 1.22 million to 0.50 million tCO₂e, while mung bean decreased from 167 thousand to only 46 thousand tCO₂e, indicating a substantial reduction in the contribution of these species over the study period. This study highlights the importance of BNF in the production of these legume species, enabling reductions in nitrogen fertilizer use, increasing economic savings, and reducing greenhouse gas emissions in these production systems, thereby contributing to the sustainability of agricultural production.