Abstract Irrigation contributes to enhance and sustain agricultural production in the U.S. across all aridity regimes, via mitigation against interannual environmental variability. Currently, a quantitative understanding of the role of irrigation in stabilizing agricultural yields is lacking, limiting the realization of irrigation-adoption impacts. Here we use >220,000 historical (1950–2015) county-year irrigated and rainfed yield records for the top-nine U.S. crops [maize (Zea mays L.), soybean (Glycine max (L.) Merr.), spring wheat (Triticum aestivum L.), winter wheat (Triticum aestivum L.), alfalfa (Medicago sativa L.), sorghum (Sorghum bicolor (L.) Moench), cotton (Gossypium hirsutum), barley (Hordeum vulgare L.) and oats (Avena sativa)]. To comprehensively quantify the “Irrigation-Induced Reduction in Crop Yield Variability” (IIRYV, defined as the percent reduction in crop yield variability when irrigated with respect to rainfed yield variability). Averaged across all crops, national-level IIRYV was 41 %, which varied from 0 to 90 % across various regions and crops. IIRYV was highly crop-specific, and maize and cotton crops demonstrated the highest and least magnitudes. IIRYV substantially varied spatially within the constituent growing regions for each crop, and thus national scale assessments masked significant spatial differences. IIRYV was subject to interannual (temporal) variability; however, in general, IIRYV increased over time (1950–2015) for most crops. These findings will help in the evaluation of the contribution of historical irrigation development policy and adoption in the U.S in mitigating external shocks (variability) in U.S. agricultural productivity. The demonstration of spatial and temporal dynamics in IIRYV will aid in irrigation-water allocations and adoption by prioritizing irrigation development for vulnerable crops and regions.

中文翻译：

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灌溉对美国农业生产力年际变化的影响

摘要 通过缓解年际环境变化，灌溉有助于提高和维持美国在所有干旱状况下的农业生产。目前，缺乏对灌溉在稳定农业产量中的作用的定量理解，限制了灌溉采用影响的实现。在这里，我们使用了超过 220,000 个历史（1950-2015）县年灌溉和雨育产量记录的前九名美国作物 [玉米 (Zea mays L.)、大豆 (Glycine max (L.) Merr.)、春小麦 ( Triticum aestivum L.)、冬小麦 (Triticum aestivum L.)、苜蓿 (Medicago sativa L.)、高粱 (Sorghum bicolor (L.) Moench)、棉花 (Gossypium hirsutum)、大麦 (Hordeum vulgare L.) 和燕麦 (燕麦）]。全面量化“灌溉引起的作物产量变异性降低”（IIRYV，定义为灌溉时作物产量变异性相对于雨育产量变异性的减少百分比）。在所有作物中，国家级 IIRYV 的平均值为 41%，在不同地区和作物中从 0% 到 90% 不等。IIRYV 具有高度的作物特异性，玉米和棉花作物表现出最高和最低的幅度。IIRYV 在每种作物的组成生长区域内在空间上有很大差异，因此国家尺度评估掩盖了显着的空间差异。IIRYV 受年际（时间）变化的影响；然而，总体而言，大多数作物的 IIRYV 随时间（1950-2015 年）增加。这些发现将有助于评估美国历史灌溉发展政策和采用在减轻美国农业生产力的外部冲击（可变性）方面的贡献。