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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #423850
Research Project: Agronomic and Engineering Solutions for Conventional and Organic Conservation Agricultural Systems in the Southeastern U.S.

Location: Soil Dynamics Research

Title: Impact of cover crops on the critical period for weed control in row crops

Author
item Price, Andrew
item CHAHAL, GOURAV - Auburn University
item Bonnell, James

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2025
Publication Date: 2/24/2025
Citation: Price, A.J., Chahal, G., Bonnell, J.C. 2025. Impact of cover crops on the critical period for weed control in row crops [abstract]. Weed Science Society of America, Vancouver, BC February 24-27 2025.

Interpretive Summary:

Technical Abstract: The rise of herbicide-resistant and troublesome weeds challenges sustainable crop production, causing the need for integrated weed management, including cover crops, to optimize weed management under conservation tillage systems. This abstract synthesizes findings from three field studies conducted at E.V. Smith Research Station, Shorter, Alabama, evaluating how high-biomass cover crops, compared to winter fallow systems (both managed with conservation tillage), influence the critical period of weed control (CPWC)—the timeframe during which crops are most vulnerable to weed competition—in corn, soybean, and cotton. The split-plot design employed having cover crop treatment as main plots and subplots assessed weed-free and weedy intervals to determine CPWC components: critical timing of weed removal (CTWR, when control must begin) and critical weed-free period (CWFP, when control can end) while preventing =5% relative yield losses. In corn, crimson clover cover crop systems shortened CPWC to 2.8 weeks in 2019 compared to 3.5 weeks in winter fallow systems. Cover crop residues delayed CTWR by suppressing early weed emergence and shortened CWFP, reducing weed biomass by 30–50% during both growing seasons. For soybean, cereal rye cover crop systems reduced CPWC to near-zero (0 weeks in 2018 and 2019) and 3.5 weeks (2020), whereas winter fallow systems required >7 weeks of control in 2018 and >6.2 weeks in 2020. Cover crop residues suppressed weeds, delayed CTWR, and enabled earlier ending of intensive weed management. In cotton, cereal rye systems delayed CTWR by 8 days compared to winter fallow, reducing weed biomass by 40–60% across years. The CPWC for cotton under cover crops began 3 weeks after planting, while winter fallow systems risked yield losses without early intervention. Cover crops consistently reduced CPWC duration across crops by altering weed emergence dynamics: residues delayed early-season weed pressure (prolonging CTWR) and suppressed biomass accumulation, allowing a theoretical earlier ending of weed control (shortening CWFP). By integrating cover crops into conservation systems, farmers can minimize herbicide reliance, mitigate resistance risks, and enhance agroecosystem resilience. This approach offers a scalable strategy to balance productivity and sustainability in row-crop agriculture.