Field studies were conducted in central Missouri and central Kansas to evaluate the crop tolerance and efficacy of various combinations of atrazine, flufenacet isoxaflutole, flumetsulam clopyralid, isoxaflutole, and S-metolachlor applied PPI or PRE in conventional-till corn. Application technique did not influence crop injury in Kansas. In Missouri, greater crop injury was observed with treatments containing isoxaflutole when applied PPI vs. PRE. Application technique influenced giant foxtail, ivyleaf morningglory, large crabgrass, Palmer amaranth, and common waterhemp control. In dry years, control of these weeds was usually either same or greater with PPI than it was with PRE treatments. In years with average to above average precipitation, isoxaflutole provided greater control as a PRE application than as a PPI application. Palmer amaranth and common waterhemp control was usually greater with atrazine, isoxaflutole, and S-metolachlor applied PRE than it was applied PPI. Differences in control of all weeds between PPI and PRE applications were less obvious with two or three herbicides compared with treatments with a single herbicide. In general, the corn yield was greater with most of the treatments having two, three, or four herbicides than it was with treatments having a single herbicide, which was due to better weed control with the tank-mixtreatments.

Nomenclature: Atrazine; clopyralid; flufenacet; flumetsulam; isoxaflutole; S-metolachlor; common waterhemp, Amaranthus rudis Sauer AMATA; giant foxtail, Setaria faberi Herrm. SETFA; ivyleaf morningglory, Ipomoea hederacea Jacq. IPOHE; large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA; Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA; corn, Zea mays L.