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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #141921
Title: IN-ROW AND BETWEEN-ROW INTERFERENCE BY CORN (ZEA MAYS) MODIFIES ANNUAL WEED CONTROL BY PREEMERGENCE RESIDUAL HERBICIDE

Author
item Donald, William
item JOHNSON, WILLIAM - UNIV OF MISSOURI
item NELSON, KELLY - UNIV OF MISSOURI

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2004
Publication Date: 9/1/2004
Citation: Donald, W.W., Johnson, W.G., Nelson, K. 2004. In-row and between-row interference by corn (zea mays) modifies annual weed control by preemergence residual herbicide. Weed Technology 18:497-504.

Interpretive Summary: The presence of row crops, such as field corn, improves herbicidal control of weeds, but the impact of weed position relative to crop rows on herbicide efficacy is unknown. This research demonstrated for the first time that corn interference enhanced soil residue herbicide control of annual weeds emerging in corn rows more than it enhanced control of weeds emerging between rows. As a consequence of corn interference with annual grass and broadleaf weeds, less herbicide was required to control weeds in corn rows than was required to provide the same extent of control between rows. This research suggests that it may be possible to reduce total herbicide use without reductions in yield or economic returns if a lower but effective herbicide rate is applied in-row than is used between rows, taking advantage of corn interference with weed growth. This fundamental research is of interest to weed scientists who design alternative methods of managing weeds in corn. It is also of interest to extension agents, farmers, herbicide manufacturers, and environmentalists who are concerned with reducing residual herbicide use in order to minimize the chance of herbicide contamination of surface water.

Technical Abstract: The presence of row crops, such as field corn, improves herbicidal control of weeds, but the impact of weed position relative to crop rows on herbicide efficacy is unknown. One research goal was to determine whether weeds emerging in corn rows responded differently to preemergence soil residual herbicides than those emerging between corn rows. A second goal was to determine whether corn yield was best modeled as a function of (a) in-row or (b) between-row or (c) both in-row and between-row total weed cover emerging after herbicide treatment at mid-season. Preemergence atrazine + s-metolachlor + clopyralid + flumesulam were broadcast at different rates (0X, 0.25 X, 0.5 X, 0.75 X and 1 X) in field corn at two sites in Missouri, with the 1X rate equal to 2.24 + 1.75 + 0.211 + 0.067 kg ai/ha, respectively. Treatment effectiveness was measured as between-row and in-row grass weed cover (primarily giant foxtail), broadleaf weed cover (primarily common waterhemp, common ragweed, common cocklebur, smartweed species and velvetleaf), total weed cover, and corn grain yield. Total weed cover was reduced by increasing herbicide rate in a dose dependent response and was as much as 20% lower in-row than between-row at both sites. As a consequence of corn interference with grass and broadleaf weeds, less herbicide was required to reduce total weed cover to the same extent in corn rows than between rows. For example, the relative herbicide rates required for 40% total weed cover at mid-season were 34 and 69% of the 1X rate in-row and between-row, respectively, at one site and 10 and 29% of the 1X rate in-row and between-row, respectively, at a second site. At both sites, corn yield loss was best modeled versus between-row total weed cover emerging after herbicide treatment, rather than both in-row and between-row total weed cover.