The use of a soybean cultivar with competitive ability combined with an equidistant plant population distribution can enhance the competitive ability of crops against weeds. Two field experiments were carried out at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul-RS, during the 2001/2002 growing season, aiming to characterize the contribution of the cultivar and row spacing to soybean competitiveness against weeds. Experiment 1 tested the competitive conditions expressed by the presence or absence of the soybean cultivar FUNDACEP 33 simulating the weed, row spacing (25 and 50 cm) and six reacting soybean cultivars. Experiment 2 tested the competitiveness conditions expressed by the presence or absence of dicotyledonous weeds, row spacing (25 and 50 cm) and soybean cultivars (IAS 5 and FEPAGRO RS 10). Besides ranking among the best producing cultivars, FEPAGRO RS 10 shows characteristics of a plant able to compete with weeds, especially taller weeds with higher dry matter and foliar mass ratio, providing a better soil coverage. Reduced row spacing allows earlier soybean soil coverage, decreases weed population and dry matter, and maintains or increases soybean grain yield.
Glycine max; row spacing; competitiveness; weeds; Bidens spp.; Sida rhombifolia
