Maize production in Thailand is increasingly suffering from drought periods along the cropping season. This creates the need for rapid and accurate methods to detect crop water stress to prevent yield loss. The study was, therefore, conducted to improve the efficacy of thermal imaging for assessing maize water stress and yield prediction. The experiment was carried out under controlled and field conditions in Phitsanulok, Thailand. Five treatments were applied, including (T1) fully irrigated treatment with 100% of crop water requirement (CWR) as control; (T2) early stress with 50% of CWR from 20 days after sowing (DAS) until anthesis and subsequent rewatering; (T3) sustained deficit at 50% of CWR from 20 DAS until harvest; (T4) late stress with 100% of CWR until anthesis and 50% of CWR after anthesis until harvest; (T5) late stress with 100% of CWR until anthesis and no irrigation after anthesis. Canopy temperature (FLIR), crop growth and soil moisture were measured at 5-day-intervals. Under controlled conditions, early water stress significantly reduced maize growth and yield. Water deficit after anthesis had no significant effect. A new combination of wet/dry sponge type reference surfaces was used for the determination of the Crop Water Stress Index (CWSI). There was a strong relationship between CWSI and stomatal conductance (R² = 0.90), with a CWSI of 0.35 being correlated to a 64%-yield loss. Assessing CWSI at 55 DAS, that is, at tasseling, under greenhouse conditions corresponded best to the final maize yield. This linear regression model validated well in both maize lowland (R² = 0.94) and maize upland fields (R² = 0.97) under the prevailing variety, soil and climate conditions. The results demonstrate that, using improved standardized references and data acquisition protocols, thermal imaging CWSI monitoring according to critical phenological stages enables yield prediction under drought stress.

中文翻译：

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热成像评估干旱条件下的玉米水分胁迫和产量预测

泰国的玉米生产越来越多地受到作物季节干旱期的影响。这就需要快速准确的方法来检测作物水分胁迫，以防止产量损失。因此，进行这项研究是为了提高热成像评估玉米水分胁迫和产量预测的功效。该实验是在泰国彭世洛的受控和现场条件下进行的。施以5个处理，包括(T1)充分灌溉处理，以100%作物需水量(CWR)作为对照；(T2) 从播种后 20 天 (DAS) 到开花和随后的再浇水，采用 50% CWR 的早期胁迫；(T3) 从 20 DAS 到收获持续赤字为 CWR 的 50%；(T4) 后期胁迫，100% CWR 直至开花，开花后 50% CWR 直至收获；(T5) 100% CWR 的后期胁迫直至开花，开花后不灌溉。每隔 5 天测量一次冠层温度 (FLIR)、作物生长和土壤水分。在受控条件下，早期水分胁迫显着降低了玉米生长和产量。开花后水分亏缺无明显影响。湿/干海绵型参考表面的新组合用于确定作物水分胁迫指数 (CWSI)。CWSI 和气孔导度之间有很强的关系（湿/干海绵型参考表面的新组合用于确定作物水分胁迫指数 (CWSI)。CWSI 和气孔导度之间有很强的关系（湿/干海绵型参考表面的新组合用于确定作物水分胁迫指数 (CWSI)。CWSI 和气孔导度之间有很强的关系（R ² = 0.90)，0.35 的 CWSI 与 64% 的产量损失相关。在 55 DAS 评估 CWSI，即在温室条件下抽穗时，最符合最终玉米产量。在普遍的品种、土壤和气候条件下，该线性回归模型在玉米低地 ( R ² = 0.94) 和玉米旱地 ( R ² = 0.97) 均得到了很好的验证。结果表明，使用改进的标准化参考和数据采集协议，根据关键物候阶段的热成像 CWSI 监测可以预测干旱胁迫下的产量。