Detecting crop irrigation status in orchard canopies with airborne and ASTER thermal imagery

This work provides a description of the research conducted to assess if ASTER satellite data enable the detection of the water status in orchard tree crops. Summer and winter TERRA-ASTER images were acquired over a study area of Seville in southern Spain over a 6-year period. 1076 olive orchards were monitored in this area, obtaining field location, area, tree density, and irrigation status information. Surface temperature images were obtained using the TES method and 0.5 m resolution panchromatic ortho-rectified imagery collected over the entire area to obtain vegetation cover. A comparison study of the temperature difference between orchards under different irrigation schemes is presented. Results in summer ASTER images showed differences between irrigated and rainfed orchard fields of 2 K, decreasing the differences to 0.5 K in ASTER winter images due to the lack of water stress condition. This methodology could be useful to detect the crop irrigation stratus operationally from ASTER satellite thermal imagery, with potential implications for evapotranspiration studies in non- homogeneous canopies.