Sustainable management of limited water resources in a young orange orchard

In the study, deficit irrigation (DI) strategies were imposed on a young orange orchard in Sicily (Southern Italy) with the aim to monitor and analyze crop physiological features, first yield and fruit quality data for possible negative effects. The orchard includes trees irrigated with drip and sub-drip irrigation systems. Irrigation strategies, based on DI concepts, including regulated deficit irrigation (RDI) and partial root-zone drying (PRD), were adopted during the irrigation seasons 2011 and 2012, each supplying different percentages of the crop evapotranspiration (ETc). Several physiological indices indicative of plant water status were analyzed during the trial, including, stem water potential, stomatal conductance, canopy temperature, trunk diameter variations, leaf area index (LAI). The imposed DI strategies allowed maximum water saving of 41% (PRD treatment), without conditioning the first yield data. Fruit composition resulted positively affected by water restrictions. The impact of the imposed deficit on trees depends mainly on its degree of severity (i.e. lowering of stem water potential above the threshold of −1.3 MPa for citrus orchards). A certain growth reduction was observed in DI treatments causing WUE (plant water use efficiency) increase, in terms of reducing competition between vegetative and reproductive growth. Subsurface drip irrigation system, designed for supplying 75% of ETc allowed plant water status, yield and quality data quite comparable with those obtained in the control treatment, supplying 100% of ETc by surface drip irrigation systems. Overall, the obtained results show that the studied DI strategies were successfully applied in a young orange orchard allowing water saving without significant detrimental effect on trees.