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Accepted manuscript

Relay intercropping of wheat and soybean improves weed control, subsequent seed rain, and economic stability in Arkansas soybean systems

Published online by Cambridge University Press:  23 April 2026

Amar S. Godar*
Affiliation:
Post Doctoral Fellow, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville site, AR, USA
Jason K. Norsworthy
Affiliation:
Distinguished Professor and Elms Farming Chair of Weed Science, Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville site, AR, USA
Tom L. Barber
Affiliation:
Professor and Extension Weed Scientist, Cooperative Extension Service, Lonoke, AR, USA
*
Author for correspondence: Amar S. Godar; E-mail: agodar@uark.edu
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Abstract

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Herbicide-resistant weeds remain a persistent challenge in soybean production across the southern United States, increasing interest in cultural practices that complement chemical control. Wheat–soybean relay intercropping (RIC) was evaluated relative to full-season soybean (FS) across three herbicide-use intensities (0-, 1-, or 2-pass POST programs) at two Arkansas sites (Fayetteville and near Colt) during the 2023 and 2024 soybean growing seasons. Weed control was assessed for Palmer amaranth and broadleaf signalgrass; weed biomass was quantified by grass and broadleaf groups, and seed production was measured for Palmer amaranth. Ground cover, cropping system yield, and economic outcomes were also evaluated. Compared with FS, RIC improved weed control most under reduced-input regimes (no herbicide or one-pass), maintaining a 6–16 % advantage even under the two-pass program. These gains corresponded to a 99% reduction in weed biomass and Palmer amaranth seed production relative to FS. RIC sustained nearly 90% ground cover during early and midseason intervals, limiting opportunities for weed seedbank recruitment and establishment. Across herbicide regimes, soybean-equivalent yield under RIC were comparable to or exceeded those of FS. Under low-input scenarios, profitability was greater under RIC because weed interference reduced FS performance; under the two-pass program, returns were similar between systems, indicating that RIC buffers economic performance when herbicide efficacy is uncertain. Break-even modeling across a wide range of crop prices further supported an economic advantage of RIC, with the largest gains under reduced-input herbicide programs. Collectively, these results indicate that RIC is operationally feasible and strengthens integrated weed management where herbicide performance is uncertain and resistance risk is elevated.

Information

Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BYCreative Common License - NCCreative Common License - ND
This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is unaltered and is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use or in order to create a derivative work.
Copyright
© The Author(s), 2026. Published by Cambridge University Press on behalf of Weed Science Society of America