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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #271839
Title: Herbicide and cover crop residue integration for amaranth control in conservation agriculture cotton and implications for resistance management

Author
item Price, Andrew
item Balkcom, Kipling
item Duzy, Leah
item KELTON, JESSICA - Auburn University

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2012
Publication Date: 7/1/2012
Citation: Price, A.J., Balkcom, K.S., Duzy, L.M., Kelton, J.A. 2012. Herbicide and cover crop residue integration for Amaranthus control in conservation agriculture cotton and implications for resistance management. Weed Technology. 26(3):490-498.

Interpretive Summary: Conservation agriculture practices are threatened by glyphosate-resistant Palmer amaranth. Integrated practices including PRE herbicides and high-residue conservation agriculture systems may decrease pigweed emergence. Early-season pigweed density was reduced in high-residue conservation tillage when compared to the winter fallow systems in two of three years. Conservation tillage utilizing high-residue cover crops increased net returns over conventional tillage by $100 ha-1 or more two out of three years at both locations. High-residue cover crop integration into a conservation tillage system provided reduced pigweed density and increased yield over winter fallow systems; the inclusion of a broadcast preemergence application provided increased early-season pigweed control and may provide additional control when glyphosate-resistant pigweed populations are present.

Technical Abstract: Conservation agriculture practices are threatened by glyphosate-resistant Palmer amaranth. Integrated practices including PRE herbicides and high-residue conservation agriculture systems may decrease Amaranth emergence. Field experiments were conducted from autumn 2006 through cash crop harvest in 2009 at two sites in Alabama to evaluate the effect of integrated weed management practices on amaranth population density, biomass and cotton yield in glyphosate-resistant cotton. Horizontal strips included four conservation agriculture systems with three cereal rye cover crop seeding dates and a winter fallow conservation system compared to a conventional tillage (CT) system. Additionally, vertical strips of four herbicide regimes consisted of: broadcast, banded or no PRE applications of S-metolachlor at 1.12 kg ai ha-1 followed by (fb) glyphosate at 1.12 kg ae ha-1 applied POST fb a LAYBY application of diuron at 1.12 kg ai ha-1 plus MSMA at 2.24 kg ai ha-1 or the LAYBY application alone. Early-season Amaranth density was reduced in high-residue CT in comparison to winter fallow systems in two of three years. Amaranth density in herbicide treatments that included a broadcast PRE application were lower at three of five sampling dates compared to banding early season PRE applications in the early-season; however, the differences were not significant during the late season and cotton yields were not affected by PRE placement. High-residue conservation tillage yields were 577 to 899 kg ha-1 more than CT except at one site in one year when CT treatment yields were higher. Conservation tillage utilizing high-residue cover crops increased net returns over conventional tillage by $100 ha-1 or more two out of three years at both locations. High-residue cover crop integration into a conservation tillage system provided reduced Amaranth density and increased yield over winter fallow systems; the inclusion of a broadcast PRE application provided increased early-season pigweed control and may provide additional control when glyphosate-resistant Amaranth populations are present.