Deficit Irrigation Strategies: Preliminary Assessment on a sicilian young orange orchard

In Mediterranean regions the economical sustainability of fruit tree crops strictly depends on the limited availability of water resources. Deficit irrigation (DI) strategies are particularly suitable to optimize water resource, improve water use efficiency by reducing crop water requirements. In the study, DI strategies were adopted on a young orange orchard in Sicily (Southern Italy) and crop physiological features were monitored and analysed for possible negative effects. The orchard includes 300, 4-years old, trees, irrigated with drip and sub-drip irrigation systems. Four irrigation strategies (replicated 3 times), based on DI concepts, were adopted, each supplying different percentages (50, 75, 100%) of the irrigation requirement (IR). IR values were calculated via the Penman-Monteith model, by assuming a crop coefficient (Kc ) of 0.45 typical for immature orchard, and correction coefficients accounting for the localized irrigation. Several physiological indices were measured during the trial, including Leaf Area Index, stem water potential, canopy temperature, and trunk diameter, among others. Preliminary observations, obtained during the two irrigation periods (2011-2012), evidenced slight variations of xylematic potential and stomata conductance among the monitored treatments. LAI, canopy volume and trunk circumference increases were quite similar among treatments. Accordingly, trees growth seems to sustain the imposed water restrictions, without significant stress symptoms on the analyzed physiological features.