Using midday stem water potential for scheduling deficit irrigation in mid-late maturing peach trees under Mediterranean conditions

Irrigation techniques that reduce water applications are increasingly applied in areas with scarce water resources. In this study, the effect of two regulated deficit irrigation (RDI) strategies on peach [Prunus persica (L.) Batsch cv. "Catherine"] performance was studied over three growing seasons. The experimental site was located in Murcia (SE Spain), a Mediterranean region. Two RDI strategies (restricting water applications at stage II of fruit development and postharvest) based on stem water potential (I-s) thresholds (-1.5 and -1.8 MPa during fruit growth and -1.5 and -2.0 MPa during postharvest) were compared to a fully irrigated control. Soil water content (theta(v)), I-s, gas exchange parameters, vegetative growth, crop load, yield and fruit quality were determined. RDI treatments showed significantly lower values of theta(v) and I-s than control trees when irrigation water was restricted, causing reductions in stomatal conductance and photosynthesis rates. Vegetative growth was reduced by RDI, as lower shoot lengths and pruning weights were observed under those treatments when compared to control. However, fruit size and yield were unaffected, and fruit quality was slightly improved by RDI. Water savings from 43 to 65 % were achieved depending on the year and the RDI strategy, and no negative carryover effect was detected during the study period. In conclusion, RDI strategies using I-s thresholds for scheduling irrigation in mid-late maturing peach trees under Mediterranean conditions are viable options to save water without compromising yield and even improving fruit quality.