A field experiment was conducted during the 1978/79 growing season at the Central Depression Region of Rio Grande do Sul, Brazil, in order to evaluate the response soybean cultivars BR1, Bragg, Davis, IAS4, IAS5, Paraná, and Planalto to metribuzin applied in pre-emergence at rates of 0, 490 and 980 g/ha. The effects of the treatments were evaluated through visual rating of phytotoxicity, counting of soybean population, and determinations of dry weight of soybean stems, number of grains per unit area and grain yield. For most of the variables measured there were reductions proportional to increasing rates of metribuzin appl ied. Results of visual evaluation of soybean injury showed statistical differences among rates of the herbicide, being Bragg and Davis the cultivars that presented the lowest injury symptons, while BR1 showed the highest degree of phytotoxicity from metribuzin. For grain yi elds, it was determined that Bragg behaved as a highly tolerant cultivar; BR1 and Davis as moderately tolerants, IAS5 as intermediate; Paraná, Planalto and IAS 4 as moderately susceptibles.
metribuzin; soybean; cultivars; tolerance; susceptibility