A tool for detecting crop water status using airborne high-resolution thermal imagery

Abstract

Knowledge on crop water status at the orchard scale is necessary for the efficient management of irrigation water. Canopy temperature has long been recognized as a plant water status indicator, and crop water stress index (CWSI), which is obtained from canopy temperature could be used as a tool for remotely detecting plant water status from airborne high-resolution thermal imagery. In 2012, CWSI baselines for olive and peach trees were derived from infrared thermometer data. An aircraft equipped with a thermal sensor flew over two orchards acquiring highresolution thermal images. At the same time, leaf water potential (ΨL) was measured in eighteen trees per specie. Relationship between the difference of canopy and air temperature (Tc-Ta) and ΨL had a R2 of 0.74 and 0.82, for peach and olive, respectively. CWSI ranged from zero to one and showed a significant correlation with ΨL. Maps of estimated ΨL (derived from CWSI - ΨL relationships) were able to detect the spatial variability of plant water status within the orchards, and may be a feasible tool for irrigation purposes.