In order to identify morphological characteristics in soybean plants that define greater competitive ability against weeds, two experiments were carried out. The first experiment was installed in Cruz Alta, RS, where soybean competed against forage radish (Raphanus sativus), and the other in Eldorado do Sul, RS, where the crop competed against beggar ticks (Bidens spp.) and arrow leaf sida (Sida rhombifolia). Results multiple linear regression and correlation analysis demonstrated that soybean plants holding with higher stem dry matter of (including leaves) at 45 days after emergency, higher dry matter of shoot at 60 days after emergency, and greater grain yield, granted superior competitiveness of soybean with forage radish. When competitors were weeds hairy beggarticks and arrowleaf sida, soybean stem dry matter (with the leaves), soil coverage by crop canopy, and grain yield, arose as the traits that conferred greater competitive ability to the crop. Plant height, branch number and branch length have also contributed for higher competition ability in soybean.
interference; Raphanus sativus; Bidens spp.; Sida rhombifolia
