Effect of deficit irrigation on early-maturing peach tree performance

The effects of different deficit-irrigation strategies on plant-water status and yield were studied for 5 years in early-maturing peach trees (cv. Flordastar) growing under Mediterranean climatic conditions. The deficit-irrigation (DI) treatments were continuous, regulated (RDI), partial root-zone drying and a soil water content-based treatment. Peach fruit yield was more affected by post-harvest irrigation than by pre-harvest irrigation. Deficit irrigation for this cultivar produced significant water savings but caused a yield penalty, with the RDI treatment showing the clearest manifestation of this. Deficit irrigation in general affected the number of fruits per tree more than fruit size. Average stem water potential threshold values for summer (July-August-September) should be maintained above -0.9 MPa if yields are not to decrease by more than 10 %. The marginal water use efficiency value of 0.07 for the irrigation range studied indicates that the maximum benefit, derived from a linear production function, will always occur at the limit of the water constraint prior to maximum yield values. Decision-makers should apply the minimal amount of irrigation water that allows maximum yields. Since DI treatments decrease yield due to smaller tree sizes, it is advisable that thinning practices be adapted when deficit irrigation is imposed.