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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #313188
Title: Factors affecting potential for Palmer amaranth (Amaranthus palmeri) suppression by winter rye in Georgia, USA

Author
item Webster, Theodore
item SIMMONS, DANIELLE - University Of Georgia
item CULPEPPER, A - University Of Georgia
item GREY, TIMOTHY - University Of Georgia
item BRIDGES, DAVID - Abraham Baldwin Agricultural College
item Scully, Brian

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2016
Publication Date: 5/4/2016
Citation: Webster, T.M., Simmons, D.B., Culpepper, A.S., Grey, T.L., Bridges, D.C., Scully, B.T. 2016. Factors affecting potential for Palmer amaranth (Amaranthus palmeri) suppression by winter rye in Georgia, USA. Field Crops Research. 192(2016)103-109.

Interpretive Summary: Herbicide resistant Palmer amaranth (Amaranthus palmeri) has rapidly become a dominant weed management issue in agronomic crops of the Southeast US. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-residue, rolled cover crop mulches, in conjunction with herbicide tools. A high-residue rolled rye cover crop appears to have merit for suppression of small-seeded broadleaf weeds, especially herbicide resistant Palmer amaranth. The use of integrated weed management systems that employ multiple control tactics have been advocated, but often adoption appears to occur only after herbicide-dominated solutions begin to fail. Success of rolled rye mulch in suppressing small-seeded broadleaf weeds will be a function of the mulch thickness, persistence, and uniformity; each of which can be affected by rye planting date. Mmaximum rye biomass in April occurred when rye was planted prior to middle-November. However, a 50% reduction in rye biomass occurred in April when rye was planted in middle-December, providing growers with a short planting interval for high-biomass rye production. Additionally, rye seeding rate did not increase rye biomass production, indicating that delays in autumn sowing cannot be overcome with plant density. Finally, nitrogen fertilizer applied at planting consistently increased rye biomass production 23 to 33% relative to non-fertilized controls, averaged over all planting dates. Additional research is needed to evaluate how high-residue cover crop systems affect weed management systems and soil moisture status in the sandy soils of the southeast Coastal Plain. Additional information on the synergistic interactions on various pests of cotton (weeds, nematodes, insects, and plant pathogens) and their control mechanisms over multiple seasons is needed to evaluate the utility, sustainability, and profitability of high-reside rye systems.

Technical Abstract: Herbicide resistant Palmer amaranth (Amaranthus palmeri) has rapidly become a dominant weed management issue in agronomic crops of the Southeast US. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-residue, rolled cover crop mulches, in conjunction with herbicide tools. Previous research demonstrated that the biomass of rolled cover crop, typically rye, is positively correlated to its ability to suppress Palmer amaranth establishment. In an effort to maximize rye biomass, three field studies were conducted in Ty Ty, GA and near Chula, GA to evaluate various factors, including planting date, seeding rate, and nitrogen application, which are known to influence rye biomass production. This research revealed that maximum rye biomass in April occurred when rye was planted prior to middle-November. However, a 50% reduction in rye biomass occurred in April when rye was planted in middle-December, providing growers with a short planting interval for high-biomass rye production. Additionally, rye seeding rate did not increase rye biomass production, indicating that delays in autumn sowing cannot be overcome with plant density. Finally, nitrogen fertilizer applied at planting consistently increased rye biomass production 23 to 33% relative to non-fertilized controls, averaged over all planting dates. Additional research is needed to evaluate how high-residue cover crop systems affect weed management systems and soil moisture status in the sandy soils of the southeast Coastal Plain.