Sustainability of pistachio production (Pistacia vera L.) under supplemental irrigation in a Mediterranean climate

The objective of this study was to examine the effects of supplemental micro-irrigation, in a commercial rainfed orchard, on tree water status, gas exchange and productivity of Pistacia vera L. (cv Bianca) grafted on P. ter-ebirahus. Irrigating with 10-15% of estimated full evaporative demand significantly increased average annual productivity by increasing yield in the on-crop year of this alternate bearing species. Irrigation increased yield by 30%, resulting in 1600 kg of in-shell product per ha. Irrigation delayed leaf senescence while flower bud abscission was not reduced until the third year of experiment. Irrigation did not improve gas exchange during Stage I (pericarp growth). Both stomata] conductance (g(s)) and maximum photosynthesis (A(max)) increased with irrigation during Stage III (intense embryo growth). Stem water potential appeared less sensitive than gas exchanges in detecting differences in water stress between treatments. The results suggest that the efficiency of irrigation can be improved taking into consideration crop load and tree phenology. The results also demonstrate pistachio production is environmentally and economically sustainable in Mediterranean areas having 500 mm rainfall, with as little as 100 mm of irrigation water.