Seed Production as Influenced by Glyphosate Applications Across a Weed Community

Authors: Walker, Eric; OLIVER, LAWRENCE - UNIVERSITY OF ARKANSAS

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2008
Publication Date: 4/1/2008
Citation: Walker, E.R., Oliver, L.R. 2008. Seed Production as Influenced by Glyphosate Applications Across a Weed Community. Weed Technology. 22:318-325

Interpretive Summary: Weeds reduce crop yields by competing with the crop for water, nutrients, and light. Successful weed management strategies target the entire weed community rather than a single weed species. However, even effective weed management strategies rarely provide complete, season-long weed control, and late-season weeds mature to produce seed that cause problems in future years. The herbicide glyphosate controls many different weed species and, when applied at flowering, reduces seed production of many weed species. Since flowering varies by individual weed species, field studies were conducted to determine the most effective glyphosate application timing to minimize seed production of a troublesome weed community. The most effective and practical treatment was a single 0.84 kg/ha glyphosate application at pitted morningglory flowering, resulting in seed reductions of greater than 90% for barnyardgrass, pitted morningglory, prickly sida, and sicklepod and 83% for Palmer amaranth. This research demonstrates that a single late-season glyphosate application can significantly and practically reduce the number of weed seed available to cause problems in crops in the future.

Technical Abstract: Late-season weed infestations often do not affect yields and are allowed to mature and contribute seed to the soil seedbank, ensuring the future establishment of competitive weed communities. Effective long-term weed management strategies must incorporate practices to reduce the soil seedbank by reducing late-season seed production by weed communities. Field studies were conducted to determine the effects of late-season glyphosate applications on seed production of barnyardgrass, Palmer amaranth, pitted morningglory, prickly sida, and sicklepod as members of a weed community. Although sequential 0.42 kg ae/ha glyphosate applications initiated by the first weed species in the community to flower and repeated every 10 d was the most effective treatment and reduced seed production of all species by more than 95%, the most practical treatment was a single 0.84 kg/ha glyphosate application at pitted morningglory flowering, resulting in seed reductions of 90, 83, 96, 96, and 99% for barnyardgrass, Palmer amaranth, pitted morningglory, prickly sida, and sicklepod, respectively. This research demonstrates that annual contributions by a weed community to the soil seedbank can be significantly and practically reduced by a single late-season glyphosate application.