Palmer amaranth (Amaranthus palmeri S. Watson) is a major biotic constraint in agronomic cropping systems in the United States. While crop–weed competition models offer a beneficial tool for understanding and predicting crop yield losses, within these models, certain weed biological characteristics and their responses to the environment are unknown. This limits understanding of weed growth in competition with crops under different irrigation methods and how competition for soil moisture affects crop growth parameters. This research measured the effect of center-pivot irrigation (CPI) and subsurface drip irrigation (SDI) on the actual evapotranspiration (ETa) of A. palmeri grown in maize (Zea mays L.), soybean [Glycine max (L.) Merr.], and fallow subplots. Twelve A. palmeri plants were alternately transplanted 1 m apart in the middle two rows of maize, soybean, and fallow subplots under CPI and SDI in 2019 and 2020 in south-central Nebraska. Maize, soybean, and fallow subplots without A. palmeri were included for comparison. Soil-moisture sensors were installed at 0-0.30, 0.30-0.60, and 0.60-0.90-m soil depths next to or between three A. palmeri and crop plants in each subplot. Soil-moisture data were recorded hourly from the time of A. palmeri transplanting to crop harvest. The results indicate differences in A. palmeri ETa between time of season (early, mid-, and late season) and crop type across 2019 and 2020. Although irrigation type did not affect subplot data, the presence of A. palmeri had an impact on subplot ETa across both years, which can be attributed to the variable relationship between volumetric soil water content (VWC) and ETa throughout the growing season due to advancing phenological stages and management practices. This study provides important and first-established baseline data and information about A. palmeri evapotranspiration and its relation to morphological features for future use in mechanistic crop–weed competition models.

长芒苋（Amaranthus palmeri S. Watson）是美国农业种植系统中的主要生物限制因素。虽然作物与杂草竞争模型为理解和预测作物产量损失提供了有益的工具，但在这些模型中，某些杂草的生物学特征及其对环境的响应是未知的。这限制了对不同灌溉方法下杂草与作物竞争生长以及土壤水分竞争如何影响作物生长参数的理解。本研究测量了中心枢轴灌溉 (CPI) 和地下滴灌 (SDI) 对玉米 ( Zea mays L.)、大豆 ( Glycine max (L.))中生长的帕尔梅里实际蒸散量 (ET a )的影响。 Merr.]，以及休闲的次要情节。2019年和2020年在内布拉斯加州中南部，在CPI和SDI条件下，将12株棕榈树每隔1 m交替移植到中间两行玉米、大豆和休耕小小区中。包括玉米、大豆和没有帕尔梅氏菌的休耕子小区进行比较。土壤湿度传感器安装在每个小区中三个棕榈树和农作物旁边或之间的 0-0.30、0.30-0.60 和 0.60-0.90 米土壤深度处。从棕榈树移植到作物收获期间，每小时记录一次土壤湿度数据。结果表明，2019 年和 2020 年季节时间（早季、中季和晚季）和作物类型之间A. palmeri ET a存在差异。虽然灌溉类型不会影响子区数据，但A. palmeri的存在会产生影响子图 ET a跨越这两年，这可以归因于由于物候阶段和管理实践的推进，整个生长季节土壤体积含水量 (VWC) 和 ET a之间的可变关系。这项研究提供了有关棕榈树蒸散量及其与形态特征的关系的重要且首次建立的基线数据和信息，以供将来在机械作物杂草竞争模型中使用。