Searching for a deficit irrigation strategy to save water and improve fruit quality without compromising pomegranate production

Deficit irrigation (DI) strategies have frequently studied in drought resistant crops to optimise water-use efficiency and save water. Four different DI strategies were studied in fifteen-year-old pomegranate trees (Punica granatum (L.) cv. Mollar de Elche) during the season of 2021: irrigation at 120 % of ETc during the whole season (control, C); irrigation at 50 % of ETc during the whole season (SDI); irrigation at 50 % of ETc during the linear fruit growth phase (RDIfg) and irrigation at 25 % of ETc during the ripening phase (RDIr). The effects of DI treatments on water relations, gas exchange, canopy temperature, yield and fruit quality were analysed. Water status of pomegranate responded closely to changes in soil water content. The reduction of leaf osmotic potential and leaf osmotic potential at full turgor to SDI, RDIfg and RDIr treatments indicated an osmotic adjustment. The stem water potential and the crop water stress index were more sensitive to water stress than gas exchange. SDI treatment increased non-marketable fruit weight and number. Nevertheless, RDIfg treatment could be considered a non-critical period because of the low sensitivity to water stress of trees, yield maintenance and the increase of nutritional organic compounds in fruits, saving 27 % of irrigation water. The application of RDIr produced the highest content of bioactive compounds, saving 8 % of water saving with a slight increase of non-marketable fruit number and weight. This suggests that the intensity and duration in which the deficit irrigation was applied could set the threshold irrigation conditions above which pomegranate production could be negatively affected.