Competitive interaction between soybean cultivars and Sida rhombifolia

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.