Efficacy, Phytotoxicity, and Persistence of Imazaquin, Imazethapyr, and Clomazone in No-Till Double-Crop Soybeans (Glycine max)

Abstract

Experiments were conducted in 1985 and 1986 to determine and compare the efficacy, phytotoxicity, and soil persistence of imazquin, imazethapyr, and clomazone in no-till double-crop soybeans. All herbicides controlled 93% or greater jimsonweed, velvetleaf, and giant foxtail. Imazaquin and imazethapyr controlled more common cocklebur and ivyleaf morningglory than clomazone. Soybeans were injured from imazaquin and imazethapyr applications in 1986 but yields were not reduced. First-order kinetics described the dissipation of each herbicide. Imazaquin and imazethapyr were more persistent in the soil than clomazone. Averaged over both years, half-lives of 10, 43, and 60 days were calculated for clomazone, imazaquin, and imazethapyr, respectively. Clomazone was not detected 10 to 20 cm in the soil profile. More imazethapyr was detected 10 to 20 cm in the soil profile than imazaquin in 1985. Slight corn injury (≤10%) was observed in 1987 following previous year applications of imazaquin to no-till double-crop soybeans but corn yields were not reduced.