Assessing Crop Water Status and Stress Response in Precision Agriculture: The Role of CCATD and CTD

Abstract

Crop temperature regulation is a fundamental aspect of plant physiology, especially under fluctuating environmental conditions. Temperature-based indices such as Crop Canopy Air Temperature Difference (CCATD) and Canopy Temperature Depression (CTD) are vital indicators of plant water status, transpiration efficiency, and drought response. CCATD, defined as the difference between canopy temperature (Tc) and air temperature (Ta), provides insights into water stress, with higher values indicating limited transpiration and increased canopy heat accumulation. In contrast, CTD—calculated as the difference between Ta and Tc—reflects the plant’s evaporative cooling capacity, where higher values denote active transpiration and efficient water use. The inverse relationship between CCATD and CTD enhances their utility in crop stress monitoring, precision irrigation, and the selection of stress-resilient genotypes in breeding programs. Advanced technologies such as infrared thermometry, UAV-mounted thermal imaging, and satellite-based remote sensing support accurate assessment of these indices at multiple scales. Environmental variables—including solar radiation, vapor pressure deficit (VPD), wind speed, and soil moisture—significantly influence CCATD and CTD, highlighting the need for their integration with multispectral and physiological data for more effective stress detection. This review emphasizes the critical role of CCATD and CTD in optimizing water management, guiding climate-resilient crop selection, and advancing precision agriculture. Future research should focus on integrating these indices with AI-driven analytics and high-throughput phenotyping to enhance their predictive value and support sustainable crop production under increasing climate variability.