Glyphosate-resistant horseweed is difficult to manage in no-tillage crop production fields and new strategies are needed. Cover crops may provide an additional management tool but narrow establishment windows and colder growing conditions in northern climates may limit the cover crop biomass required to suppress horseweed. Field experiments were conducted in 3 site-years in Michigan to investigate the effects of two fall-planted cover crops, cereal rye and winter wheat, seeded at 67 or 135 kg ha−1, to suppress horseweed when integrated with three preplant herbicide strategies in no-tillage soybean. The preplant strategies were control (glyphosate only), preplant herbicide without residuals (glyphosate + 2,4-D), and preplant herbicide with residuals (glyphosate + 2,4-D + flumioxazin + metribuzin). Cereal rye produced 79% more biomass and provided 12% more ground cover than winter wheat in 2 site-years. Increasing seeding rate provided 41% more cover biomass in 1 site-year. Cover crops reduced horseweed density 47% to 96% and horseweed biomass by 59% to 70% compared with no cover at the time of cover crop termination. Cover crops provided no additional horseweed suppression 5 wk after soybean planting if a preplant herbicide with or without residuals was applied, but reduced horseweed biomass greater than 33% in the absence of preplant herbicides. Cover crops did not affect horseweed suppression at the time of soybean harvest or influence soybean yield. Preplant herbicide with residuals and without residuals provided at least 52% and 20% greater soybean yield compared with the control at 2 site-years, respectively. Cereal rye and winter wheat provided early-season horseweed suppression at biomass levels below 1,500 kg ha−1, lower than previously reported. This could give growers in northern climates an effective strategy for suppressing horseweed through the time of POST herbicide application while reducing selection pressure for horseweed that is resistant to more herbicide sites of action.

中文翻译：

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整合秋季种植的谷物覆盖作物和种植前除草剂，用于大豆中的抗草甘膦马草（Conyza canadensis）管理

在免耕作物生产领域难以管理草甘膦抗性马草，需要新的策略。覆盖作物可以提供额外的管理工具，但北方气候条件下狭窄的种植窗口和较冷的生长条件可能会限制抑制马草所需的覆盖作物生物量。在密歇根州进行了 3 个地点年的田间试验，以研究两种秋季种植的覆盖作物谷物黑麦和冬小麦的效果，播种面积为 67 或 135 公斤公顷-1，在免耕大豆中与三种种植前除草剂策略相结合时抑制杂草。种植前策略是控制（仅草甘膦）、种植前无残留除草剂（草甘膦 + 2,4-D）和种植前有残留除草剂（草甘膦 + 2,4-D + 氟噻嗪 + 灭草灵）。与冬小麦相比，谷物黑麦在 2 个地点年的生物量增加了 79%，地面覆盖增加了 12%。增加播种率在 1 个地点年提供了 41% 的覆盖生物量。与覆盖作物终止时没有覆盖相比，覆盖作物降低了 47% 至 96% 的马草密度和 59% 至 70% 的马草生物量。种植大豆后 5 周，如果施用有或没有残留的种植前除草剂，覆盖作物没有提供额外的马草抑制，但在没有种植前除草剂的情况下，马草生物量减少了 33% 以上。覆盖作物不影响大豆收获时的马草抑制或影响大豆产量。在 2 个地点年，与对照相比，有残留和无残留的种植前除草剂分别提供至少 52% 和 20% 的大豆产量。谷物黑麦和冬小麦在生物量水平低于 1,500 公斤公顷时提供了早季马草抑制作用-1，低于先前报道的。这可以为北方气候的种植者提供一种有效的策略，在 POST 除草剂应用期间抑制马草，同时降低对更多除草剂作用位点具有抗性的马草的选择压力。