Effects of different irrigation regimes on vegetative growth, yield and fruit quality of young pomegranate (Punica granatum ‘Wonderful’) trees

In this study, a field experiment was conducted during two successive seasons (2017 and 2018) and corresponded to the first two years of 'Wonderful' pomegranate plant growth, when water irrigation management is a critical aspect for the successful cultivation for commercial production. In semiarid regions of Italy, water is a scarce resource and its efficient use has to be prioritize. The trial was designed with the objective to search for an optimum irrigation scheduling by analyzing the effects of four different irrigation regimes (100, 75, 50, and 25% of crop evapotranspiration (ETc) on young trees to optimize vegetative growth, yield and fruit quality. The pomegranate commercial orchard (5.5x3 m apart), drip irrigated, was located in the countryside of Foggia (Apulia region, Southern Italy). Weekly values of ETo and kc, estimated by climatological data with the shaded area approaches, were used. Results showed that after two consecutive seasons the largest increase of the trunk girth (73.8 mm) was obtained in the 100% ETc treatment that resulted significantly higher than in the 75, 50 and 25% ETc ones (62.6, 60.5 and 57.7 mm, respectively). Annual shoot growth, total yield per tree, number of fruits per tree and size of fruits, recorded only on the second season, decreased significantly with the restriction of ETc water volumes applied to the crop. While, total polyphenols and antioxidant activity in pomegranate juices were higher in the water deficit treatments (average 4359 mg GAE L-1 and 37.99 mol TE L-1, respectively) than the full irrigated one (3466 mg GAE L-1 and 29.39 mol TE L-1, respectively). Finally, minor differences among irrigation treatments in the soluble solids, pH and color of fruit skins, arils and juices were observed.