Monitoring of Water Requirement Using Thermal Unmanned Aerial Vehicle (UAV) on Intensive Hazelnut Orchard

Monitoring the soil water dynamic on highly intensive orchard is very important to improve the sustainability of hazelnut production. Traditionally this dynamic was monitored using only soil water content sensors. In this study, twelve soil water content sensors (SM100) and a thermal UAV (DJI Mavic 3T) were used to assess the water requirements and abiotic stress status of two cultivars (Tonda Francescana® and Tonda Giffoni) and of three plant densities (2500, 1250 and 625 tree ha-1) in a 7 years old and grafted hazelnut orchard. The analysis was conducted on Central Italy, where the hottest temperature is generally registered in July, when the water requirements are maximum. The thermal UAV data were used to define a thermal map and a Crop Water Stress Index (CWSI). The thermic data underlined that the orchard was not under stress conditions, even if an increasing trend was observed with higher plant densities. A different behavior between the two cultivars was evident. In fact, the CWSI values measured on Tonda Francescana ® plant were significantly higher than those obtained for Tonda Giffoni ones, still below the stress threshold, meaning a different water use. The monitoring of the hazelnut canopy temperatures and CWSI allows to manage the irrigation based on the plant densities as well as on the cultivar, avoiding stress condition, that might determine yielding losses.