To quantify water stress on coffee trees, leaf water potential (LWP) measurements are commonly performed in a Scholander chamber; however, this methodology is restricted to research activities, due to the difficulty of measurement in the field: sampling hours at predawn and intensive work. A crop water stress index (CWSI) based on leaf temperature has been used as indicative of LWP in several crops, and thermal images can be a precious tool for mapping LWP under intensive drip‐irrigated coffee areas, in order to adjust irrigation requirements according to soil moisture spatial variability. This study aims to define the relationships between the water potential of coffee leaf based on CWSI, calculated by means of a portable infrared sensor and a thermal camera, analysing correlation, precision and accuracy indexes. The study was conducted in Piracicaba, SP, Brazil, using Coffea arabica species of the Catuaí Red variety IAC 144 that was drip irrigated using tensiometers as matric potential sensors. The observed CWSI and LWP presented good correlations in the linear and cubic models. It was concluded that the CWSI is a good indicator of the water potential of a coffee canopy and can be an alternative to measurements of LWP from the Scholander chamber. © 2020 John Wiley & Sons, Ltd.

中文翻译：

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滴灌条件下冠层对咖啡植物水分亏缺的热响应

为了量化咖啡树上的水分胁迫，通常在Scholander箱中进行叶水势（LWP）测量。但是，由于该方法难以进行实地测量，因此该方法仅限于研究活动：黎明前的采样时间和密集的工作。基于叶片温度的作物水分胁迫指数（CWSI）已被用作几种作物中LWP的指标，并且热图像可以作为在密集滴灌咖啡区域下绘制LWP的宝贵工具，以便根据以下要求调整灌溉需求土壤水分空间变异性。这项研究旨在定义基于CWSI的咖啡叶水势之间的关系，该关系通过便携式红外传感器和热像仪进行计算，并分析相关性，精度和准确性指标。CatuaíRed品种IAC 144的阿拉伯咖啡种，使用张力计作为基质电势传感器进行滴灌。线性模型和三次模型中观察到的CWSI和LWP呈现出良好的相关性。得出的结论是，CWSI是咖啡冠层水势的良好指标，并且可以代替Scholander箱中LWP的测量。分级为4 +©2020 John Wiley＆Sons，Ltd.