The effect of regulated deficit irrigation on tree water use and growth of peach

Abstract

Tree water use (TWU) of peach (Prunus persica L. Batsch) was studied over two years in drainage lysimeters. Trees were three years old and 3.5 m high at the outset of the experiment. Single trees were grown in individual lysimeters and sited and guarded to resemble a 4 x 1 m, high-density orchard. The effect of different irrigation strategies on TWU and growth were measured relative to a Control (non-limiting irrigation) treatment. Regulated Deficit Irrigation (RDI) is a strategy which controls vegetative vigour in high- density orchards by reducing irrigation early in the season. TWU under RDI was less than the Control over the entire season, this decline being 50% during slow fruit growth (i.e. during RDI treatment) and 30% when all treatments were irrigated to maintain drainage (post-RDI). While vegetative vigour was reduced under RDI, yield of RDI trees irrigated daily was similar to Control trees. Differences in TWU during RDI was partially explained by water availability, plant water status and stomatal conductance and post- RDI by differences in tree size, total leaf area and micro-advection. RDI trees irrigated twice daily used water more efficiently than trees irrigated weekly. RDI with saline water (25,50 and 100 mS m“1) reduced both TWU and tree performance in Year 2. The coefficients for E pan replacement (Kc), for the Control trees were 1.47 (Year 1) and 1.56 (Year 2). In both years TWU followed a similar pattern to harvest, reaching a plateau at 3-4 weeks before harvest.