Palmer amaranth is the most common and troublesome weed in North Carolina sweetpotato. Field studies were conducted in Clinton, NC, in 2016 and 2017 to determine the critical timing of Palmer amaranth removal in ‘Covington’ sweetpotato. Palmer amaranth was grown with sweetpotato from transplanting to 2, 3, 4, 5, 6, 7, 8, and 9 wk after transplanting (WAP) and maintained weed-free for the remainder of the season. Palmer amaranth height and shoot dry biomass increased as Palmer amaranth removal was delayed. Season-long competition by Palmer amaranth interference reduced marketable yields by 85% and 95% in 2016 and 2017, respectively. Sweetpotato yield loss displayed a strong inverse linear relationship with Palmer amaranth height. A 0.6% and 0.4% decrease in yield was observed for every centimeter of Palmer amaranth growth in 2016 and 2017, respectively. The critical timing for Palmer amaranth removal, based on 5% loss of marketable yield, was determined by fitting a log-logistic model to the relative yield data and was determined to be 2 WAP. These results show that Palmer amaranth is highly competitive with sweetpotato and should be managed as early as possible in the season. The requirement of an early critical timing of weed removal to prevent yield loss emphasizes the importance of early-season scouting and Palmer amaranth removal in sweetpotato fields. Any delay in removal can result in substantial yield reductions and fewer premium quality roots.

中文翻译：

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甘薯中棕榈苋（Amaranthus palmeri）去除的关键时机

帕尔默苋菜是北卡罗来纳州甘薯中最常见和最麻烦的杂草。2016 年和 2017 年在北卡罗来纳州克林顿市进行了实地研究，以确定在“科文顿”甘薯中去除帕尔默苋菜的关键时机。从移栽到移栽后 2、3、4、5、6、7、8 和 9 周（WAP），棕榈苋与甘薯一起种植，并在本季的剩余时间内保持无杂草。随着帕尔默苋菜的去除延迟，帕尔默苋菜的高度和枝条干生物量增加。帕尔默苋菜干扰的长期竞争在 2016 年和 2017 年分别降低了 85% 和 95% 的可销售产量。甘薯产量损失与帕尔默苋菜高度呈强烈的反线性关系。观察到 2016 年和 2017 年每厘米帕尔默苋菜的产量下降 0.6% 和 0.4%，分别。去除 Palmer 苋菜的关键时间，基于 5% 的可销售产量损失，是通过将对数逻辑模型拟合到相对产量数据来确定的，并确定为 2 WAP。这些结果表明，帕尔默苋菜与甘薯具有很强的竞争力，应在本季尽早进行管理。为防止产量损失而要求及早清除杂草的关键时间强调了在甘薯田中早季侦察和除草苋菜的重要性。任何延迟移除都可能导致产量大幅下降和优质根系减少。这些结果表明，帕尔默苋菜与甘薯具有很强的竞争力，应在本季尽早进行管理。为防止产量损失而要求及早清除杂草的关键时间强调了在甘薯田中早季侦察和除草苋菜的重要性。任何延迟移除都可能导致产量大幅下降和优质根系减少。这些结果表明，帕尔默苋菜与甘薯具有很强的竞争力，应在本季尽早进行管理。为防止产量损失而要求及早清除杂草的关键时间强调了在甘薯田中早季侦察和除草苋菜的重要性。任何延迟移除都可能导致产量大幅下降和优质根系减少。