S12 - Session O2 - Remote and proximal sensing techniques to support precision irrigation in the olive orchard

Authors: Giovanni Caruso *, Giacomo Palai, Letizia Tozzini, Simone Priori, Riccardo Gucci

Water availability is the main limiting factor for orchards in the Mediterranean region. Although olive ( Olea europaea L.) trees are drought tolerant, many studies showed the beneficial effects of irrigation on vegetative growth, yield components, and oil quality. The aim of this study was to evaluate the potential use of remote and proximal sensing techniques in supporting the precision irrigation of olive orchards. Experiments were carried out in two high density olive orchards in Tuscany where three irrigation regimes (full irrigation, deficit irrigation and rainfed conditions) were applied. An unmanned aerial vehicle equipped with a multispectral and a thermal camera was used to measure the canopy normalized difference vegetation index (NDVI) and the crop water stress index (CWSI), whereas two different proximal soil sensors were used to map the soil spatial variability. In experiment 1 UAV imagery allowed to properly monitor the tree growth (canopy volume) and water status (CWSI). A significant relationship (R 2 = 0.70) between stem water potential (SWP) and CWSI was measured. In experiment 2 we identified two clusters of trees, based on NDVI and ECa measurements, showing differences in fruit yield and annual trunk cross sectional area (TCSA) increment. The higher tree productivity measured in Cluster 1 also resulted in a higher water use efficiency for fruit (WUE f of 0.90) and oil (WUE o of 0.32) compared to Cluster 2 (0.67 and 0.27 for WUE f and WUE o , respectively). In conclusion, our results showed that: i) UAV multispectral and thermal images can be efficiently used to monitor the canopy growth and tree water status in the olive orchard; ii) tree vigour plays a major role in determining the final fruit yield under optimal soil water availability, whereas soil features become the most important factors under rainfed conditions.