Intensified cover-cropping practices are increasingly viewed as a herbicide-resistance management tool but clear distinction between reactive and proactive resistance management performance targets is needed. We evaluated two proactive performance targets for integrating cover-cropping tactics, including (1) facilitation of reduced herbicide inputs and (2) reduced herbicide selection pressure. We conducted corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] field experiments in Pennsylvania and Delaware using synthetic weed seedbanks of horseweed [Conyza canadensis (L.) Cronquist] and smooth pigweed (Amaranthus hybridus L.) to assess winter and summer annual population dynamics, respectively. The effect of alternative cover crops was evaluated across a range of herbicide inputs. Cover crop biomass production ranged from 2,000 to 8,500 kg ha−1 in corn and 3,000 to 5,500 kg ha−1 in soybean. Experimental results demonstrated that herbicide-based tactics were the primary drivers of total weed biomass production, with cover-cropping tactics providing an additive weed-suppression benefit. Substitution of cover crops for PRE or POST herbicide programs did not reduce total weed control levels or cash crop yields but did result in lower net returns due to higher input costs. Cover-cropping tactics significantly reduced C. canadensis populations in three of four cover crop treatments and decreased the number of large rosettes (>7.6-cm diameter) at the time of preplant herbicide exposure. Substitution of cover crops for PRE herbicides resulted in increased selection pressure on POST herbicides, but reduced the number of large individuals (>10 cm) at POST applications. Collectively, our findings suggest that cover crops can reduce the intensity of selection pressure on POST herbicides, but the magnitude of the effect varies based on weed life-history traits. Additional work is needed to describe proactive resistance management concepts and performance targets for integrating cover crops so producers can apply these concepts in site-specific, within-field management practices.

中文翻译：

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将覆盖作物整合为主动抗除草剂管理工具的替代绩效目标

强化覆盖种植实践越来越多地被视为一种除草剂抗性管理工具，但需要明确区分反应性和主动性抗性管理绩效目标。我们评估了两个整合覆盖种植策略的主动绩效目标，包括（1）促进减少除草剂投入和（2）减少除草剂选择压力。我们进行了玉米（玉米L.) 和大豆 [最大甘氨酸(L.) Merr.] 在宾夕法尼亚州和特拉华州使用马草的合成杂草种子库进行田间试验 [加拿大白粉虱(L.) Cronquist] 和光滑的藜 (苋菜L.) 分别评估冬季和夏季的年度人口动态。在一系列除草剂投入中评估了替代覆盖作物的效果。覆盖作物生物量产量为 2,000 至 8,500 公斤公顷-1在玉米和 3,000 至 5,500 公斤公顷-1在大豆中。实验结果表明，基于除草剂的策略是总杂草生物量生产的主要驱动力，而覆盖种植策略提供了附加的杂草抑制效益。用 PRE 或 POST 除草剂计划替代覆盖作物并没有降低总杂草控制水平或经济作物产量，但由于投入成本较高，确实导致净回报降低。显着减少覆盖种植策略C.canadensis在种植前除草剂暴露时，四种覆盖作物处理中的三种的种群减少了大莲座丛（直径> 7.6厘米）的数量。用覆盖作物替代 PRE 除草剂导致对 POST 除草剂的选择压力增加，但在 POST 施用时减少了大型个体（>10 cm）的数量。总的来说，我们的研究结果表明覆盖作物可以降低 POST 除草剂的选择压力强度，但影响的大小因杂草生活史特征而异。需要做更多的工作来描述主动抗性管理概念和整合覆盖作物的性能目标，以便生产者可以将这些概念应用于特定地点的田间管理实践。