To minimize the chance of surface water contamination by herbicides, farmers need alternative ways to manage weeds in field crops, such as field corn, that reduce herbicide use. Zone herbicide application (ZHA) reduces herbicide use compared with conventional broadcast herbicide application by (1) banding low herbicide rates between corn rows (≤ 1× normal broadcast registered rate), (2) managing crops to favor crop competition, and (3) banding very low herbicide rates over crop rows (≪ 1× normal rate). The research goal was to compare the relative effectiveness of reduced-rate ZHA with broadcast herbicide application on in-row (IR) and between-row (BR) summer annual weed cover (chiefly giant foxtail and waterhemp species), grain yields, and net returns resulting from herbicide application in field corn. Preemergence ZHA of atrazine metolachlor clopyralid flumesulam was made in zones (i.e., even width bands) at different rates between and over crop rows for three site-years in Missouri, and the 1× rate was 2.24 1.75 0.211 0.067 kg ai ha−1, respectively. Best ZHA treatments (0.29× to 0.30× IR herbicide rates 0.74× to 0.80× BR herbicide rates) outperformed all reduced-rate broadcast herbicide treatments (0.25×, 0.5×, and 0.75×) based on net returns in partial budget analysis. Yields for highest yielding ZHA could not be distinguished from the 1× broadcast treatments in two of three site-years. Net returns due to herbicide application for the highest yielding ZHA were comparable with the 1× broadcast treatment in all three site-years. For the best ZHA, the 3-yr average for total herbicide applied per unit was 53% of the 1× broadcast rate. ZHA may provide row crop farmers with a new generic option for reducing herbicide rates and input costs while maintaining net returns and reducing the chance of surface water contamination by herbicides.
Nomenclature: Atrazine; clopyralid; flumetsulam; glufosinate; metolachlor; giant foxtail, Setaria faberii (L.) Beauv. SETFA; common waterhemp, Amaranthus rudis Sauer AMATA; corn, Zea mays L., ‘Pioneer 33G28’.