Efficacy of reduced-rate herbicide combinations in dry-seeded rice (Oryza sativa) on alluvial clay soil

Research was conducted from 1993 through 1995 to evaluate barnyardgrass control, rice yield, and estimated economic return with POST applications of propanil or propanil + molinate applied alone or with quinclorac. Herbicides were applied under a variety of water management practices and environmental conditions at rates ranging from 1.1 to 3.4, 1.7 to 5.6, and 0.17 to 0.40 kg ai ha(-1) for propanil, propanil + molinate, and quinclorac, respectively. Reduced-rate combinations of propanil or propanil + molinate with reduced rates of quinclorac controlled small, actively growing barnyardgrass and provided yields and estimated economic returns similar to combinations of these herbicides at higher rates when irrigated. When herbicides were applied to larger barnyardgrass, propanil + molinate at 5.6 kg ha(-1) was more effective than propanil at 3.4 kg ha(-1) or quinclorac at 0.40 kg ha(-1) applied alone. Propanil + molinate applied with quinclorac at 0.28 or 0.40 kg ha(-1) controlled barnyardgrass more effectively and provided higher yields and greater estimated economic returns than propanil at 3.4 kg ha(-1), propanil + molinate at 5.6 kg ha(-1), quinclorac at 0.17, 0.28, or 0.40 kg ha(-1), or combinations of propanil and quinclorac.