Morphysiological and Nutritional Responses of Bean Cultivars in Competition with <em>Digitaria insularis</em>

Studies exploring the competitive interaction between common beans and weeds are essential to adopt more efficient management strategies in the field, thereby reducing production costs. This study aimed to evaluate the competitive ability of bean cultivars in the presence of sourgrass (Digitaria insularis), using different plant proportions in associations. The experiments were conducted in a greenhouse, arranged in a randomized block design with four replications, during the 2020/21 crop season. Treatments were organized in plant proportions of beans and sourgrass: 100:0, 75:25, 50:50, 25:75, and 0:100%. The competitiveness analysis was carried out using replacement series diagrams and relative competitiveness indices. At 50 days after emergence (DAE), measurements were taken for leaf area, plant height, gas exchange, shoot dry mass, and nutrient concentration in bean leaves. The results indicated an equivalence in competition mechanisms and resource demand between beans and weeds when coexisting. Bean cultivars showed similar competitive abilities when associated with sourgrass. Gas exchange and nutrient content in beans were negatively affected by increasing weed density. Beans exhibited higher relative growth than the weed when in association. Interspecific competition caused more harm to morphophysiological and nutritional variables than intraspecific competition.