SOYBEAN (GLYCINE-MAX) AND ROTATIONAL CROP RESPONSE TO PPI CHLORIMURON, CLOMAZONE, IMAZAQUIN, AND IMAZETHAPYR

Field studies were conducted from 1989 to 1992 to evaluate soybean and rotational crop tolerance to PPI applications of chlorimuron (23 to 140 g ai/ha), clomazone (560 to 3360 g/ha), imazaquin (70 to 420 g/ha), and imazethapyr (53 to 310 g/ha). Soybean injury was evident only in 1989. Soybean height reduction 45 d after application increased linearly with increasing rates of chlorimuron, imazaquin, and imazethapyr. Chlorimuron at 140 g/ha and imazaquin at 420 g/ha reduced soybean height 120 d after planting. None of the herbicides influenced soybean density. Chlorimuron and imazaquin reduced soybean seed yield linearly as rates increased. None of the herbicides reduced subsequent wheat yield. Com height reduction increased as the rate of imazaquin and imazethapyr increased. Imazethapyr and imazaquin caused 2 to 40% and 1 to 12% height reduction at 30 d after planting, respectively. Imazethapyr at 310 g/ha applied the previous year reduced com height at 120 d after planting. There were no differences in com density. Imazaquin and imazethapyr at 420 and 310 g/ha, respectively, applied the previous year reduced corn yield.