The characterization of soybean competitive ability, as a function of cultivar differential response, may provide valuable information for genetic crop improvement as well as weed management. Various crop characteristics may be associated with competitivity; however, in soybean, only a few studies have been carried out to identify them. A field experiment was conducted in Cruz Alta-RS during 2000/2001 to evaluate variability in soybean cultivars for competitivity against concurrent plants and to identify those holding superior competitive ability. Two competition conditions were tested (absence and presence of forage radish during the period of soybean vegetative development), combined with 11 soybean cultivars. The presence of forage radish during the first 60 days of crop development reduced soybean plant height, leaf area, shoot dry weight, and branch emission and growth. Soybean cultivars reacted differently to forage radish interference, suggesting the existence of genetic variability for competitivity, which allows for selection of soybean genotypes holding superior competitive ability. On the other hand, a greater growth suppression of forage radish plants was verified when associated with soybean cultivars 'CD 201' and 'Fepagro RS 10'.
Glycine max; competitive ability; genotypes; forage radish
