Combination of proximal and remote sensing methods for mapping water stress conditions of grapevine

In recent years, optical sensing techniques have been widely spread since they allow the non-invasive evaluation of water deficit stress in a timely fashion. In this study, innovative services and support systems to farmers for optimising irrigation, scheduling and practices were tested in two vineyards located in Usini and Arzachena (Sardinia, Italy). Four different irrigation treatments were applied to three grapevine cultivars and physiological observations were integrated and combined with remote sensing measurements carried out with a modified Mikrokopter UAV equipped with a multispectral camera to obtain vegetation indices (e.g., NDVI) and thermal cameras to measure water deficit stress indices. In addition, an automated digital imaging system collected high-resolution vegetation images at daily intervals and the changes in plant colour coordinates (RGB) due to changes in vine phenological stage and water status were detected. The indices obtained from remote sensing observations were then related with stem water potential, photosynthesis and chlorophyll fluorescence measurements. In general, calculated CWSI increased in stressed treatments (dry and T2), while the wet treatment yielded the lowest CWSI and SWP, as expected. Preliminary results indicated that net photosynthesis declined under high stress conditions (T2 and dry) and when CWSI values increased. ExG values showed high differences between the two irrigation treatments of up to 60% in 'Vermentino, while this behaviour was less stable for 'Cagnulari'. The tested techniques were able to detect the physiological status of plants, indicating the usefulness of remote and proximal sensing techniques to monitor vine water deficit stress.