Submitted to: Weed Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/7/2004
Publication Date: 9/1/2004
Citation: Donald, W.W., Archer, D.W., Johnson, W.G., Nelson, K. 2004. Zone herbicide application controls weeds and reduces residual herbicide use in corn. Weed Science. 52:821-833. Interpretive Summary: Throughout the Corn Belt, the herbicides atrazine and metolachlor persist in the soil and can contaminate surface and ground water. To minimize the chance of water contamination by herbicides, Corn Belt farmers need alternative ways to manage weeds in field crops, such as corn and sorghum (milo), that reduce herbicide use. One way to reduce total herbicide use is by zone herbicide application. Zone herbicide application does this by (1) banding low herbicide rates between corn rows (less than normal rate), (2) managing crops to improve crop competitiveness with weeds, and (3) banding very low herbicide rates over crop rows (much less than normal registered broadcast herbicide rate). Zone herbicide and conventional broadcast application of atrazine and metolachlor were compared for controlling giant foxtail and common waterhemp, major weeds, in field corn in Missouri. Some zone herbicide application treatments controlled weeds well. Corn yielded the same with these zone herbicide application treatments at reduced rates as with broadcast-applied herbicide at the normal rate in two of three site-years. But, net returns are more important than yield to farmers. Net returns for the highest-yielding zone herbicide application at reduced rates equaled the broadcast treatment at the normal rate in all three site-years in partial budget analysis. In terms of net return, the best zone herbicide application (i.e., in-row herbicide rate at 30% of the normal rate + between-row herbicide rate at 75% of the normal rate) controlled annual weeds very well and outperformed all reduced-rate broadcast herbicide treatments (25, 50, and 75% of normal rates). The best zone herbicide application reduced total herbicide use to 53% of the broadcast normal rate averaged over three years. Zone herbicide application gives farmers a new way to reduce herbicide use and input costs while maintaining net returns. These applied results should interest farmers, extension agents, herbicide manufacturers, weed scientists, and environmentalists who wish to minimize herbicide contamination of surface water.
Technical Abstract: Zone herbicide application (ZHA) reduces total soil residual herbicide use per unit area by (1) banding herbicide over crop rows at reduced rates (<< 1X registered rates) and (2) banding the same herbicide at higher rates between rows (< 1X registered rates) than over crop rows in combination with (3) crop management to enhance crop competitiveness with weeds. Thus, total herbicide applied per area is reduced by ZHA compared to broadcast application. The goal of this research was to determine the impact of reduced rate-ZHA on in-row and between-row summer annual weed cover (chiefly giant foxtail and waterhemp species), grain yield, and net return to herbicide applications in field corn. PRE ZHA of atrazine + metolachlor + clopyralid + flumesulam were made in zones (= even width bands) at different rates between and in crop rows at three site-years in Missouri. The 1X rate of atrazine +s-metolachlor + clopyralid + flumetsulam was 2.24 + 1.75 + 0.211 + 0.067 kg ai ha**-1, respectively. Best ZHA treatments [0.29 to 0.30X in-row (IR) herbicide rates + 0.74 to 0.80X between-row (BR) herbicide rates)] outperformed all reduced rate broadcast herbicide treatments (0.25, 0.5 and 0.75X) based on net returns in partial budget analysis. Mid-season IR and BR total weed cover for the best ZHA were similar to reduced rate broadcast treatments, and were greater than the 1X broadcast treatments. Yields for highest yielding ZHA could not be distinguished from the 1X broadcast treatments in two of three site-years. Net returns to herbicide application for the highest yielding ZHA were comparable to the 1X broadcast treatment in all three site-years. For the best ZHA, total herbicide applied per unit averaged 53% of the 1X broadcast rate averaged over three years (43, 58, and 64% of the 1X broadcast rate for separate site-years). Zone herbicide application may provide row crop farmers with a new option for reducing herbicide rates and input costs while maintaining net returns and lessening the chance of surface water contamination by herbicides.