Field studies were conducted in 2019 and 2020 to compare the effects of shade cloth light interception and Palmer amaranth (Amaranthus palmeri S. Watson) competition on ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Treatments consisted of a seven by two factorial arrangement, in which the first factor included shade cloth with an average measured light interception of 41%, 59%, 76%, and 94% and A. palmeri thinned to 0.6 or 3.1 plants m−2 or a nontreated weed-free check; and the second factor included shade cloth or A. palmeri removal timing at 6 or 10 wk after planting (WAP). Amaranthus palmeri light interception peaked around 710 to 840 growing degree days (base 10 C) (6 to 7 WAP) with a maximum light interception of 67% and 84% for the 0.6 and 3.1 plants m−2 densities, respectively. Increasing shade cloth light interception by 1% linearly increased yield loss by 1% for No. 1, jumbo, and total yield. Yield loss increased by 36%, 23%, and 35% as shade cloth removal was delayed from 6 to 10 WAP for No. 1, jumbo, and total yield, respectively. F-tests comparing reduced versus full models of yield loss provided no evidence that the presence of yield loss from A. palmeri light interception caused yield loss different than that explained by the shade cloth at similar light-interception levels. Results indicate that shade cloth structures could be used to simulate Covington sweetpotato yield loss from A. palmeri competition, and light interception could be used as a predictor for expected yield loss from A. palmeri competition.

中文翻译：

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评估遮光布模拟甘薯苋菜（Amaranthus palmeri）比赛

2019年和2020年进行了实地研究，比较了遮光布遮光效果和帕尔默苋菜（苋菜S.Watson)'Covington'红薯比赛[番薯(L.) 林]。处理由七乘二的因子排列组成，其中第一个因子包括遮光布，平均测得的光截获率为 41%、59%、76% 和 94%，以及A. 帕尔梅里细化至 0.6 或 3.1 株 m-2或未经处理的无杂草检查；第二个因素包括遮光布或A. 帕尔梅里种植后 6 或 10 周的清除时间（WAP）。苋菜光拦截在 710 至 840 生长期日（以 10 C）（6 至 7 WAP）左右达到峰值，0.6 和 3.1 株的最大光拦截为 67% 和 84% m-2密度，分别。将遮光布光拦截增加 1% 会使 1 号、大块和总产量的产量损失线性增加 1%。产量损失分别增加了 36%、23% 和 35%，因为 1 号、大型和总产量的遮光布去除时间从 6 WAP 延迟到 10 WAP。F- 比较减少和完整的产量损失模型的测试没有提供证据表明存在产量损失A. 帕尔梅里遮光造成的产量损失与类似遮光水平下的遮光布所解释的不同。结果表明，遮光布结构可用于模拟 Covington 甘薯产量损失A. 帕尔梅里竞争和光拦截可用作预期产量损失的预测因子A. 帕尔梅里竞赛。