Irregular rainfall, rising temperatures and changing frequency and intensity of extreme weather events are projected to reduce crop yields and threaten food security across the tropical monsoon sub-region. However, the anticipated extent of impact on crop yields and crop water productivity (CWP) is not yet thoroughly understood. The impacts of climate change on rice yields and CWP are assessed over the Northern Tonle Sap Basin in Cambodia by applying the AquaCrop model into the mid- (2041–2070) to long-future (2071–2099) under two Representative Concentration Pathways (RCPs) (4.5 and 8.5). Short (95 days), medium (125 days) and long (155 days) cycle varieties are tested during the wet and dry seasons. An assessment of different sowing dates and irrigation strategies (fixed and net irrigation during the dry season) elucidated the variation in response to changing environmental conditions. Higher yields (+15% by 2041–2070 and +30% by 2071–2099) and CWP values (+42% by 2071–2099) are expected if using short-cycle varieties, in particular when sown in July. Dry season rice yields are also projected to increase (+28% by 2071–2099), especially under a higher greenhouse gas emission scenario (RCP 8.5) compared to a medium emission scenario (RCP 4.5) as a result of the CO₂ fertilization effect. Depending on the climatic scenario, rice variety, irrigation scheme, and sowing date, increasing heat and drought-stress conditions are likely to have different impacts on rice yields and CWP over time. Overall, this study highlights the benefits of adjusting crop calendars to identify the most suitable irrigation schedules and rice varieties to effectively adapt to projected future climate.

中文翻译：

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模拟气候变化对柬埔寨雨季和旱季稻米的影响

预计降雨不规律、气温升高以及极端天气事件的频率和强度不断变化将降低作物产量并威胁整个热带季风次区域的粮食安全。然而，对作物产量和作物水分生产力 (CWP) 的预期影响程度尚未完全了解。通过将 AquaCrop 模型应用到中期（2041-2070 年）到长期（2071-2099 年）的两条代表性集中路径（RCP），评估了气候变化对柬埔寨北部洞里萨盆地的水稻产量和 CWP 的影响) (4.5 和 8.5)。短（95 天）、中（125 天）和长（155 天）周期品种在雨季和旱季进行测试。对不同播种日期和灌溉策略（旱季固定灌溉和净灌溉）的评估阐明了对环境条件变化的响应变化。如果使用短周期品种，特别是在 7 月播种，预计单产会更高（到 2041-2070 年增加 15%，到 2071-2099 年增加 30%）和 CWP 值（到 2071-2099 年增加 42%）。旱季稻米产量预计也将增加（到 2071-2099 年增加 28%），特别是在温室气体排放量较高的情景（RCP 8.5）下，与中等排放情景（RCP 4.5）相比，由于 CO2₂施肥效果。根据气候情景、水稻品种、灌溉方案和播种日期，随着时间的推移，高温和干旱胁迫条件的增加可能对水稻产量和 CWP 产生不同的影响。总体而言，这项研究强调了调整作物日历以确定最合适的灌溉计划和水稻品种以有效适应预计的未来气候的好处。