First
Author: LIU Hongjie
Corresponding Author: SONG Wenlong
Journal: Remote Sensing
Abstract
Accurate monitoring of drought threshold value at different growth stages of crop is of great importance for drought monitoring. In this study, using a UAV system equipped with high-resolution thermal infrared and multispectral sensors, canopy temperature (Tc) was extracted for the winter wheat cultivar Weilong 169 at three key growth stages. Based on Tc, the canopy temperature difference (ΔT) was calculated, and the crop water stress index (CWSIsi) was developed.
Using field experimental data, Tc and CWSIsi were applied to monitor drought threshold value at different growth stages. Results show that canopy temperature (Tc) derived from the normalized difference vegetation index-Otsu method (NDVI-OTSU) had strong correlation with ground temperature measured (R2 = 0.94). For drought stress classification of winter wheat, CWSIsi proved to be more stable than ΔT. The ranges of CWSIsi thresholds under different drought stress at different growth stages were as follows:
Jointing–booting stage: threshold values under no stress, mild stress, moderate stress, and severe stress conditions are <0.30, 0.30–0.42, 0.42–0.48, and >0.48, respectively. Heading–flowering stage: <0.33, 0.33–0.47, 0.44–0.53, and >0.53. Filling–maturity stage: <0.41, 0.41–0.54, 0.54–0.59, and >0.59.These results demonstrate that the UAV-derived canopy temperature method can significantly improve the accuracy of drought monitoring and hold great potential for early identification of crop drought disasters.
Keywords: Drought classification; UAV thermal infrared; Threshold value; CWSIsi; Yield; Winter wheat
