Effects of partial root-zone drying and deficit irrigation on yield, quality and water productivity of Washington Naval orange

Internet of Things (IoT) based precision irrigation system has proven to be promising tool for optimizing water use and crop production.In this study, two irrigation water-saving techniques, double-line drip irrigation (DI) and partial-root zone drying (PRD) were assessed on 27-year-old Washington Naval orange trees.Four strategies of irrigation based on crop water requirements (100, 75, 50, and 25% of ETc) were applied in the maturity stage of growth development (phase III).Soil water contents were monitored in real-time using 10HS sensors and the Zentra cloud IoT system.Results showed that the water availability in the soil approaches the TAW threshold for DI-50%, DI-25%, PRD-50%, and PRD-25% treatments, while it remains relatively higher than RAW for the other treatments.Deficit irrigation regimes did not significantly affect the final tree yield and the irrigation water productivity (WPirrig).Nevertheless, PRD mean values were slightly higher than those under DI treatments.Regarding fruit quality parameters, results revealed that the treatments PRD-75%, PRD-50% and PRD-25% yielded significantly higher fruit flesh firmness compared to fully irrigated and DI treatments.Despite the clear decline in titratable acid (TA) trait with increasing stress level, no significant difference among treatments was registered for maturity index (MI).Our results mirror a better adaptation of orange trees to water-saving irrigation under PRD than DI.However, further and deeper research in this direction is required for more efficient irrigation water use, enhancing citrus yield and organoleptic properties.