In a context of severe water scarcity and high uncertainty of available irrigation water, the sustainable management of both irrigation and nutrient inputs to the crop become necessary. The main objective of the present study was to determine the mid-term effect of water and nutrient restrictions using different plant water status indicators of yield and quality of flat peaches. Three treatments were tested: (i) control (CTL), irrigated at ~100% of crop evapotranspiration (ETc) during the entire season; (ii) a first regulated deficit irrigation treatment (RDI1), irrigated as the CTL, except during the second fruit growth stage (~70% ETc) and late post-harvest (~50% ETc), with the same fertilization as CTL; (iii) and a second RDI treatment (RDI2), irrigated as RDI1, but with a reduction in N-P-K fertilizer units proportional to the reduction of post-harvest irrigation. During the first and second water deficit periods, an average weekly reduction of 43 and 109 m3 ha-1, respectively, allowed water savings of 33.6% in the two RDI treatments with respect to well-watered trees. Irrigation water use efficiency increased by 45%, reaching values of around 4.16 kg m–3, and nutrient use efficiency also increased by 46% for N and P, and 34% for K. Therefore, the optimization of irrigation water and nutrient inputs in semi-arid conditions was achieved, by considering that the post-harvest period in this crop is a non-critical phenological period, with a stem water potential threshold value of around –1.4 MPa, and by monitoring the reduction of nutrients provided by reducing irrigation, as this could affect the crop water status and yield. Dynamic deficit irrigation protocols according to the water availability were developed.