Integrated strategies for management of glyphosate-resistant (GR) horseweed are needed to reduce reliance on herbicides. Planting a cover crop after corn or soybean harvest in the Upper Midwest may reduce horseweed establishment and growth. Experiments were conducted in Michigan to determine if cereal rye and winter wheat, seeded at 67 or 135 kg ha−1, and terminated with glyphosate at 1.27 kg ae ha−1 1 wk before planting (early termination) or 1 wk after soybean planting (planting green) would suppress establishment and growth of GR horseweed. Cover-crop biomass was 212% to 272% higher when termination was delayed by planting green compared with early termination. At the time of termination, cover crops reduced GR horseweed biomass 41% to 89% compared with no cover. Planting green increased the C:N ratio of cover-crop residue, which improved residue persistence and GR horseweed suppression at the time of POST herbicide application, approximately 5 wk after planting. Planting green reduced GR horseweed biomass 46% to 93% compared with no cover at the time of POST herbicide application; early termination provided less consistent suppression. Cover crops alone did not suppress GR horseweed through soybean harvest. Soybean yield was 30% to 108% greater when planting green compared with early termination at 2 site-years. Cereal rye and winter wheat, seeded at 67 or 135 kg ha−1, provided early-season GR horseweed suppression. Results from this research indicate that the practice of planting green may improve GR horseweed suppression through the time of POST herbicide application.

中文翻译：

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秋季种植谷物覆盖作物终止时间对抗草甘膦马草（Conyza canadensis）抑制的影响

需要综合战略管理抗草甘膦 (GR) 马草，以减少对除草剂的依赖。在中西部上部玉米或大豆收获后种植覆盖作物可能会减少马草的生长和生长。在密歇根州进行了实验，以确定谷物黑麦和冬小麦是否播种为 67 或 135 公斤公顷-1，并以 1.27 kg ae ha 的草甘膦终止-1种植前 1 周（提前终止）或大豆种植后 1 周（种植绿色）会抑制 GR 马草的建立和生长。与提前终止相比，通过种植绿色延迟终止时，覆盖作物的生物量高出 212% 至 272%。在终止时，覆盖作物与无覆盖相比，将 GR 马草生物量减少了 41% 至 89%。种植绿色增加了覆盖作物残茬的 C:N 比，从而提高了 POST 除草剂施用时的残茬持久性和 GR 马草抑制，大约在种植后 5 周。与 POST 除草剂施用时不覆盖相比，种植绿色减少了 GR 马草生物量 46% 至 93%；提前终止提供了不太一致的抑制。仅覆盖作物并没有通过大豆收获抑制 GR 马草。与 2 个地点年的提前终止相比，种植绿色时大豆产量高出 30% 至 108%。谷物黑麦和冬小麦，播种量为 67 或 135 公斤公顷-1，提供早季 GR 杂草抑制。这项研究的结果表明，在施用除草剂后，种植绿色植物可能会改善对 GR 马草的抑制作用。