Dose–Response Curves of KIH-485 for Preemergence Weed Control in Corn

Field experiments were conducted in Nebraska with the experimental herbicide KIH-485 on soils with three different levels of organic matter (OM) to ascertain a dose response for weed control and corn tolerance. Dose–response curves based on the log-logistic model were used to determine the effective dose that provides 90% weed control (ED 90 values) for three grasses (green foxtail, field sandbur, large crabgrass) and two broadleaf weeds (velvetleaf, tall waterhemp). The ED 90 values for green foxtail control were 143, 165, and 202 g ai/ha for soils with 1, 2, and 3% OM, respectively at 28 d after treatment (DAT). The highest dose of 371 g ai/ha was needed for field sandbur control at 28 DAT, compared with 141 g ai/ha for large crabgrass, 152 g ai/ha for tall waterhemp, and 199 g ai/ha for velvetleaf. There was no significant corn injury observed. Grain yield increased with increasing doses of KIH-485; optimum yield was achieved at about 195 g ai/ha. From the dose–response curves it is clear that the proposed label rate of KIH-485 of 200 to 300 g ai/ha will provide excellent control of most grasses and certain broadleaf weeds in corn for at least the first 4 wk of the growing season on soils up to 3% OM in the state of Nebraska.