EVALUATION OF WEED CONTROL PROVIDED BY THREE WINTER CEREALS IN CONSERVATION-TILLAGE SOYBEAN

Authors: Price, Andrew; Reeves, Donald; PATTERSON, MICHAEL - AUBURN UNIVERSITY

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2005
Publication Date: 9/17/2006
Citation: Price, A.J., Reeves, D.W., Patterson, M.G. 2006. Evaluation of weed control provided by three winter cereals in conservation-tillage soybean. Renewable Agriculture and Food System. 21(3):159-164.

Interpretive Summary: The increased use of conservation tillage in soybean production requires information be developed on the role of cover crops in weed control. ARS scientists at the Soil Dynamics Research Unit in Auburn, AL and the J. Phil Campbell Sr. Natural Resource Conservation Center, in cooperation with scientists from Auburn University's Cooperative Extension System conducted a field study in Alabama to evaluate the impact of three winter cereal cover crops on weed control and soybean yield in a high-residue conservation tillage production system. A new cover crop from Brazil, black oat, along with rye and wheat were evaluated for their weed-suppressive characteristics compared to a winter fallow system. The cover crops were layed flat on the soil surface with a mechanical roller to form a dense mulch prior to soybean planting. No cover crop was effective in controlling weeds without a herbicide program. However, when black oat or rye was used and a herbicide was applied immediately after soybean planting, weed control was similar to a system that included a second herbicide application. Rye and black oat provided more effective weed control than wheat. This information can be used by State Cooperative Extension Systems, USDA-NRCS, crop consultants, and producers to promote the use of environmentally and economically sustainable conservation practices that reduce herbicide inputs on the 4.2 million acres of soybean grown in the Southeast.

Technical Abstract: Information is needed on the role of cover crops as a weed control alternative due to the high adoption of conservation-tillage in soybean [Glycine max (L.) Merr.] production. Field experiments were conducted from fall, 1994 through fall, 1997 in Alabama to evaluate three winter cereal cover crops in a high-residue conservation-tillage, soybean production system. Black oat (Avena strigosa Schreb.), rye (Secale cereale L.), and wheat (Triticum aestivum L.) were evaluated for their weed-suppressive characteristics compared to a winter fallow system. Three herbicide systems were utilized: no herbicide, a mixture of two preemergence (PRE) herbicides, or PRE plus postemergence (POST) herbicides. The PRE system contained pendimethalin at 0.84 kg ha-1 a.i. plus metribuzin at 0.43 kg ha-1 a.i. The PRE plus POST system contained pendimethalin at 0.84 kg ha-1 a.i. plus a prepackage of metribuzin at 0.39 kg ha-1 a.i. and chlorimuron ethyl at 0.06 kg ha-1 a.i. applied PRE, followed by an additional chlorimuron ethyl POST application at 8.75 g ha-1 a.i. No cover crop was effective in controlling weeds without a herbicide. However, when black oat or rye was utilized with only PRE herbicides, weed control was similar to the PRE plus POST input system. Rye and black oat provided more effective weed control in PRE only herbicide input system than wheat in conservation-tillage soybean. The winter fallow, PRE plus POST herbicide input system yielded significantly less soybean one out of three years compared to systems that included a winter cover crop.