Determination of Water Stress in Wheat Crops by Thermal Images Under Mediterranean Conditions

Canopy temperature is used as an indicator of plant water stress. In recent years, technological advances have allowed improved applications in agriculture from temperature sensors clamped on leaves to short-range remote-sensing, such as infrared thermometry and thermal imaging. There are many scientific studies on the use of thermal imaging to determine crop water stress; however, no study on wheat crops has been found in the literature. Therefore, this study aimed to determine the detectability of water stress in wheat by using thermal images. In the experiment, drainage-type, weighable lysimeters were used to make precise irrigations and obtain components of the water budget for calculating the plant water consumption. Wheat crops were grown under four different irrigation levels including no water stress as control (I-100), mild water stress (I-75), moderate water stress (I-50), and severe water stress (I-25). When the thermal images were examined, it can be seen that pre-irrigation images reflect water stress conditions better than post-irrigation. The warm color distribution was more evident under severe water stress, whereas cold colors were dominant under no water stress. During the experimental period, the plant leaf temperatures varied from 17.5 to 34.2 degrees C, while the spike temperatures ranged from 26.6 degrees C to 36.3 degrees C. The lowest plant leaf and spike temperature values were observed under control, whereas the highest values were obtained under severe water stress. It can be said that thermal cameras that provide fast and contactless data acquisition have the potential to be used in detecting water stress in wheat crops.