Abstract Sunflower (Helianthus annuus L.) has been used as an alternative summer crop in the traditional wheat (Triticum aestivum L.)-fallow rotation in the Great Plains of the USA. However, few studies have been conducted to quantify sunflower productivity and water productivity (WP) under semi-arid conditions and projected climate change. Experiments were conducted in 2008, 2010, and 2011 on sunflowers under deficit irrigation to meet a fraction of crop evapotranspiration (ETc) as estimated by FAO-56 in eastern Colorado. The field data was used to calibrate and validate the CSM-CROPGRO-Sunflower model that is incorporated in the Root Zone Water Qualify Model (RZWQM2). The calibrated model was then used to simulate sunflower production under projected climate conditions with four Representative Concentration Pathways (RCP) scenarios (2.6, 4.5, 6.0, and 8.5) and four irrigation levels (100%, 60%, 40% ETc and rainfed) in the late 21st century. The results showed that the model was able to adequately simulate sunflower biomass, yield, and soil water storage under the different irrigation treatments in all three years. The corresponding relative root mean square deviation (RRMSD) values were between 0.05 and 0.15 for the simulations of soil water storage, yield, and biomass. Under future climate change conditions, the model simulated greater impact of irrigation treatments than RCP scenarios on sunflower production. For example, yield was 3251.3, 2638.85 and 1937.17 kg ha−1 with 100%, 60% and 40% ETc irrigation under baseline (1992–2013) and was 2932.47, 2360.53 and 1810.65 kg ha−1 with these irrigation treatments under RCP8.5 (2070–2091). Simulation results also showed that scheduling irrigations based on 60% of ETc was the best choice for sunflower WP in eastern Colorado. Climate change did not affect sunflower biomass, yield, and WP. There was an increasing trend of irrigation amount was simulated from the baseline to RCP8.5 scenario to maintain a certain percent of ETc due to high temperature projected. For instance, the irrigation amount for 100%, 60% and 40% of ETc irrigation treatment was 16.4%, 17.3%, and 20.0% higher under RCP8.5 than those under baseline conditions with CO2 fertilization. Finally, our results demonstrated that RZWQM2 can be used to effectively schedule sunflower irrigations based on crop evapotranspiration requirement.

中文翻译：

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在 RZWQM2 中使用 CSM-CROPGRO-Sunflower 模拟亏缺灌溉和气候变化对科罗拉多州东部向日葵生产的影响

摘要 向日葵 (Helianthus annuus L.) 已被用作美国大平原传统小麦 (Triticum aestivum L.) 休耕轮作的替代夏季作物。然而，很少有研究在半干旱条件和预计的气候变化下量化向日葵生产力和水生产力 (WP)。2008 年、2010 年和 2011 年在欠缺灌溉条件下对向日葵进行了试验，以满足粮农组织-56 估计的科罗拉多东部作物蒸散量 (ETc) 的一小部分。田间数据用于校准和验证 CSM-CROPGRO-Sunflower 模型，该模型包含在根区水质鉴定模型 (RZWQM2) 中。然后使用校准模型模拟预测气候条件下的向日葵生产，具有四种代表性浓度途径 (RCP) 情景（2.6、4.5、6。0 和 8.5）和 21 世纪后期四种灌溉水平（100%、60%、40% ETc 和雨养）。结果表明，该模型能够充分模拟所有三年不同灌溉处理下的向日葵生物量、产量和土壤蓄水量。对应的相对均方根偏差 (RRMSD) 值介于 0.05 和 0.15 之间，用于模拟土壤储水量、产量和生物量。在未来的气候变化条件下，该模型模拟了灌溉处理对向日葵生产的影响比 RCP 情景更大。例如，产量为 3251.3、2638.85 和 1937.17 kg ha-1，在基线（1992-2013）下使用 100%、60% 和 40% ETc 灌溉，在这些 RCP 下为 2932.47、2360.53 和 1810.65 kg ha-1。 5 (2070-2091)。模拟结果还表明，基于 60% ETc 的调度灌溉是科罗拉多州东部向日葵 WP 的最佳选择。气候变化不影响向日葵生物量、产量和可湿性粉剂。由于预测的高温，模拟灌溉量从基线到RCP8.5情景有增加的趋势，以保持一定百分比的ETc。例如，100%、60%和40% ETc灌溉处理的灌溉量在RCP8.5下比在CO2施肥的基线条件下高16.4%、17.3%和20.0%。最后，我们的结果表明，RZWQM2 可用于根据作物蒸发蒸腾需求有效地安排向日葵灌溉。和WP。由于预测的高温，模拟灌溉量从基线到RCP8.5情景有增加的趋势，以保持一定百分比的ETc。例如，100%、60%和40% ETc灌溉处理的灌溉量在RCP8.5下比在CO2施肥的基线条件下高16.4%、17.3%和20.0%。最后，我们的结果表明，RZWQM2 可用于根据作物蒸发蒸腾需求有效地安排向日葵灌溉。和WP。由于预测的高温，模拟灌溉量从基线到RCP8.5情景有增加的趋势，以保持一定百分比的ETc。例如，100%、60%和40% ETc灌溉处理的灌溉量在RCP8.5下比在CO2施肥的基线条件下高16.4%、17.3%和20.0%。最后，我们的结果表明，RZWQM2 可用于根据作物蒸发蒸腾需求有效地安排向日葵灌溉。5 比使用 CO2 施肥的基线条件下的那些。最后，我们的结果表明，RZWQM2 可用于根据作物蒸发蒸腾需求有效地安排向日葵灌溉。5 比使用 CO2 施肥的基线条件下的那些。最后，我们的结果表明，RZWQM2 可用于根据作物蒸发蒸腾需求有效地安排向日葵灌溉。