Competitive Responses of Rye Cultivars When Grown in Coexistence With Weeds

Competitive ability is an essential component of integrated management, as it expresses the capacity of crops to compete efficiently for resources against weed species. Therefore, this study aimed to evaluate the competitive ability of rye cultivars BRS Serrano, BRS Progresso, and BR1 when grown in coexistence with the weeds Italian ryegrass (Lolium multiflorum) and wild radish (Raphanus raphanistrum), at different plant proportions in the associations. The combinations between the crop and the weeds followed proportions of 100-0, 75-25, 50-50, 25-75, and 0-100%, or 20-0, 15-5, 10-10, 5-15, and 0-20 plants per pot, defined in preliminary (additive) experiments. At 45 days after emergence, gas exchange, leaf area (LA), and shoot dry mass (DM) of the species were evaluated. Competitiveness was estimated using replacement series diagrams and relative competitiveness indices. Rye cultivars showed greater competitive ability than the weeds, causing more pronounced reductions in the LA and DM of Italian ryegrass and wild radish. The physiological performance of rye was less affected when infested with Italian ryegrass and more affected in the presence of wild radish, especially for cultivar BR1. Interspecific competition was more detrimental than intraspecific competition, causing significant reductions in the species. On average, competition reduced rye DM by about 45% and weed DM by 15% compared with non-competitive conditions. Wild radish caused greater losses in LA, DM, and gas exchange of rye compared with Italian ryegrass, confirming its higher competitive aggressiveness.