Konzen, Alessandro creator Galon, Leandro creator Weirich, Sabrina Natalia creator Gallina, Alessandra creator Brunetto, Leonardo creator Brandler, Daiani creator Piazzetta, Hugo von Linsingen creator Aspiazú, Ignácio creator text periodical abstract or summary bl. continuing eng ABSTRACT: The arrow-leaf sida (Sida rhombifolia), in addition to competing with soybeans, which causes productivity losses, is also host to the whitefly, which transmits viruses. The aim was to evaluate the competitive ability of soybean cultivars in the presence of an arrow-leaf sida biotype, with different proportions of plants in the association. The experiments were conducted in a completely randomized design, with four replications. Tested competitors included arrow-leaf sida with the four soybean cultivars in proportions crop:weed of 100:0; 75:25; 50:50; 25:75; and 0:100. Competitiveness analysis was carried out using diagrams applied to replacement series experiments in addition to the relative competitiveness indices. At 50 days after the emergence of the species, the variables height, diameter, leaf area, and dry mass of shoots were evaluated. Competition occurred between soybean cultivars in the presence of arrow-leaf sida, regardless of the plant proportion, causing reductions in all variables evaluated. Interspecific competition causes greater damage to al variables studied than intraspecific competition. There was competition for the same resources between soybean and arrow-leaf sida. Key words: arrow-leaf sida; competitive ability; Glycine max L RESUMO: A guanxuma (Sida rhombifolia), além de competir com a soja pelos recursos do meio causando redução da produtividade, é hospedeira da mosca branca, que transmite viroses. Objetivou-se avaliar a habilidade competitiva de cultivares de soja na presença de um biótipo de guanxuma, em diferentes proporções de plantas na associação. Os experimentos foram conduzidos em delineamento experimental completamente casualizado, com quatro repetições. Os competidores testados incluíram a guanxuma e quatro cultivares de soja nas proporções de 100:0; 75:25; 50:50; 25:75 e 0:100 cultura: planta daninha. Efetuou-se a analise da competitividade por diagramas aplicados a experimentos substitutivos, mais os indices de competitividade relativas. Aos 50 dias após a emergência das espécies, avaliou-se as variáveis altura, diâmetro de caule, área foliar e massa seca da parte aérea das plantas. Ocorreu competição entre as cultivares de soja na presença de guanxuma, independentemente da proporção de plantas, provocando reduções nas variáveis avaliadas. A competição interespecífica causa maiores prejuízos a todas as váriaveis estudadas do que a intraespecífica. Houve competição pelos mesmos recursos do meio entre a soja e a guanxuma. Palavras-chave: guanxuma; habilidade competitiva; Glycine max L Publicação online; 26 ref.; 4 illus.; 2 tables; Summaries (En, Pt) SOJA ERVA DANINHA GUANXUMA COMPETIÇÃO BIOLÓGICA Recife-PE Universidade Federal Rural de Pernambuco 2006 2026-2072 1981-1160 BR2026000612 v. 16(2) p. 1-10; (2021) http://www.agraria.pro.br/ojs32/index.php/RBCA/article/view/v16i2a8975/449 http://www.agraria.pro.br/ojs32/index.php/RBCA/article/view/v16i2a8975/449 BR-BrBNA 260518 20260518193252.0 eng