Nitrogen is the most important nutrient in the production of cotton (Gossypium hirsutum L.). Field studies on N use efficiency usually focus on recovery efficiency of added N fertilizer or agronomic N use efficiency. The internal N use efficiency of N (iNUE; lint yield divided by plant N uptake) is less studied but is a key component of N fertilizer recommendations. The objective of this study was to identify the optimum iNUE for irrigated cotton in West Texas and Arizona. Eighteen site-years of data from N fertilizer management studies from Lubbock, TX, and Maricopa, AZ, from 2000 to 2018 were used. Lint yields with N-fertilized plots averaged 1,535 and 1,790 kg ha^–1 for West Texas and Arizona, respectively. Corresponding N uptake averaged 128 and 177 kg N ha^–1 for West Texas and Arizona, reflecting average N fertilizer rates of 91 and 133 kg N ha^–1. An optimum iNUE of 12.3 ± 0.5 kg lint kg plant N^–1 was estimated by a linear-plateau model of lint yields vs. total N uptake. Optimum iNUE corresponded to 1,800 kg lint ha^–1 yield and 146 ± 5 kg N ha^–1 plant uptake. Nitrogen uptake by cotton plants greater than this was theoretically luxury uptake. Updated data on optimum iNUE can feed directly into improving current N fertilizer recommendations based on pre-plant soil NO₃ tests. In turn, this can translate to greater profits for cotton producers in the southwestern United States and the reduction in export of N from irrigated cotton fields.

中文翻译：

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美国西南部灌溉棉花的最佳内部氮利用效率

氮是棉花（Gossypium hirsutum L.）生产中最重要的营养元素。氮素利用效率的田间研究通常侧重于添加氮肥的回收效率或农艺氮素利用效率。N 的内部氮利用效率（iNUE；皮棉产量除以植物 N 吸收量）的研究较少，但它是氮肥建议的关键组成部分。本研究的目的是确定西德克萨斯和亚利桑那州灌溉棉花的最佳 iNUE。使用了来自德克萨斯州拉伯克和亚利桑那州马里科帕 2000 年至 2018 年氮肥管理研究的十八个地点年的数据。在西德克萨斯和亚利桑那州，施氮肥的地块的皮棉产量平均分别为 1,535 和 1,790 kg ha ^–1。相应的 N 吸收量平均为 128 和 177 kg N ha ^–1西德克萨斯州和亚利桑那州，反映了 91 和 133 kg N ha ^{–1 的}平均氮肥施用量。12.3 ± 0.5 kg lint kg 植物 N ^–1的最佳 iNUE是通过皮棉产量与总氮吸收的线性平台模型估算的。最佳 iNUE 对应于 1,800 kg 皮棉 ha ^–1产量和 146 ± 5 kg N ha ^–1植物吸收量。棉花植物比这更大的氮吸收理论上是奢侈的吸收。最佳 iNUE 的更新数据可以直接用于改进基于种植前土壤 NO ₃测试的当前氮肥建议。反过来，这可以转化为美国西南部棉花生产商的更大利润以及灌溉棉田氮出口的减少。