Tolerance of Three Soybean (Glycine max) Cultivars to Metribuzin

‘Tracy′, ‘Tracy-M′, and ‘Centennial′, soybean [Glycine max (L.) Merr.] cultivars were evaluated under greenhouse and field conditions for their tolerance to metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5 (4H)-one]. The I50 (50% injury) concentration of metribuzin, as determined in nutrient culture, for Tracy-M was more than three times the I50 for Tracy, but was equivalent to the I50 for Centennial. Data from greenhouse and field studies on Sharkey clay and Dundee silt loam soils indicated that Tracy-M was more tolerant to metribuzin than its parent selection, Tracy, but no more tolerant than Centennial when metribuzin was applied preplant soil incorporated or surface preemergence alone or in combination with several dinitroaniline herbicides.