Inoculação com Rhizobium tropici para reduzir a adubação nitrogenada na cultura do feijão-comum

Abstract

Common bean (Phaseolus vulgaris L.) is an essential crop for food security due to its nutritional value, but it has high nitrogen demand, making nitrogen fertilization one of the main production costs. Inoculation with nitrogen-fixing bacteria such as Rhizobium tropici is a sustainable alternative to reduce the reliance on mineral fertilizers. This study aimed to evaluate the reduction of nitrogen fertilization in bean plants inoculated with R. tropici without compromising grain yield. The experiment was conducted in a greenhouse under a randomized block design, with increasing nitrogen doses (0 to 100% of the recommended rate) combined with seed inoculation with R. tropici, and a non-inoculated control. Evaluations included nodule number, root dry mass, yield components, grain productivity, nitrogen use efficiency (NUE), and marginal economic return. Intermediate nitrogen doses (50–60% of the recommended rate) yielded the best agronomic performance, with substantial increases in nodulation, root development, and production, surpassing by more than 200% the yield obtained at 100% mineral nitrogen. The optimal dose for maximum productivity was estimated at 52.7%, while the highest economic return occurred at 52.74% (63.29 kg ha⁻¹). Nitrogen use efficiency decreased as nitrogen doses increased, indicating greater efficiency at reduced rates. The results demonstrate that inoculation with R. tropici enables up to 50% reduction in nitrogen fertilization in common bean, improving productivity, nutrient efficiency, and profitability, while promoting more sustainable agricultural practices.