Herbicide and Cover Crop Residue Integration forAmaranthusControl in Conservation Agriculture Cotton and Implications for Resistance Management

Abstract

Conservation agriculture (CA) practices are threatened by glyphosate-resistant Palmer amaranth. Integrated control practices including PRE herbicides and high-residue CA systems can decreaseAmaranthusemergence. Field experiments were conducted from autumn 2006 through crop harvest in 2009 at two sites in Alabama to evaluate the effect of integrated weed management practices onAmaranthuspopulation density and biomass, cotton yield, and economics in glyphosate-resistant cotton. Horizontal strips included four CA systems with three cereal rye cover crop seeding dates and a winter fallow (WF) CA system compared to a conventional tillage (CT) system. Additionally, vertical strips of four herbicide regimes consisted of: broadcast, banded, or no PRE applications ofS-metolachlor (1.12 kg ai ha−1) followed by (fb) glyphosate (1.12 kg ae ha−1) applied POST fb layby applications of diuron (1.12 kg ai ha−1) plus MSMA (2.24 kg ai ha−1) or the LAYBY application alone. Early-seasonAmaranthusdensity was reduced in high-residue CA in comparison to the CA WF systems in 2 of 3 yr.Amaranthusdensities in herbicide treatments that included a broadcast PRE application were lower at three of five sampling dates compared to banding early-season PRE applications; 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−1more than CT, except at one site in 1 yr when CT treatment yields were higher. CA utilizing high-residue cover crops increased net returns over CT by $100 ha−1or more 2 out of 3 yr at both locations. High-residue cover crop integration into a CA system reducedAmaranthusdensity and increased yield over WF systems; the inclusion of a broadcast PRE application can increase early-seasonAmaranthuscontrol and might provide additional control when glyphosate-resistantAmaranthuspopulations are present.

Integrated Palmer Amaranth Management in Glufosinate-Resistant Cotton: I. Soil-Inversion, High-Residue Cover Crops and Herbicide Regimes

“…Different cereal rye varieties were planted due to seed availability; Wrens Abruzzi has been shown to be more allelopathic [62]. In 2009 and 2010, frequent rain delayed both the harvesting of cotton and subsequent planting of cover crops [36]. Cereal rye cover was fertilized using 34 kg·ha −1 of a 33-0-0 fertilizer.…”

“…However, the return to conventional tillage to control glyphosate-resistant Palmer amaranth threatens to reduce conservation tillage practices. Some researchers [35,36] advocate the integration of traditional and alternative weed control strategies, such as the utilization of crop and herbicide rotation and integration of high residue cereal cover crops in order to sustain conservation tillage practices.…”

Integrating Cover Crops and POST Herbicides for Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Control in Corn

“…However, recent interest in cover crops is primarily attributed to the potential for early season weed control (Norsworthy et al 2011;Price et al 2012). Cover crops have provided some suppression of early season weeds in several crops, including cotton (Gossypium hirsutum L.), corn, and soybean [Glycine max (L.) Merr.]…”

Weed management in cotton (Gossypium hirsutum L.) through weed-crop competition: A review

“…The interaction of other weed management options and herbicides should be evaluated. Rotating cotton with crops of high residue cover would reduce early emergence of weeds and integrating this with narrow row spacing would yield desired results as late emerging weeds may have to face intense competition from cotton (Price et al, 2012(Price et al, , 2016.…”