Abstract 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.
Godar et al. (Thu,) studied this question.