The present study aimed at investigating the effect of deficit irrigation and mulching on morpho-physiological and biochemical characteristics of 15-year-old Konservolia olive trees in Dallaho Olive Research Station in Kermanshah province, Iran, in 2014 and 2015. The experiments were conducted in factorial randomized complete block design with three replications. The first factor included irrigation treatments (100% irrigation [control], 75% deficit irrigation, and 50% deficit irrigation) and the second one included mulches (polyethylene, organic [straw], and no mulch). The results clarified that there is a significant difference between deficit irrigation and mulch treatments due to their effects on the characteristics measured in this study. The highest current season shoot growth and diameter was observed in presence of 100% irrigation and straw and polyethylene mulches. Increasing water stress decreased relative water content and chlorophyll content, while using straw and polyethylene mulches increased them, compared with the mulch-free condition. Increasing water stress enhanced ionic leakage, proline content, soluble sugars, phenol content, and malondialdehyde, while using mulches reduced these characteristics. As a result, deficit irrigation can be performed without any damages to the trees if it is accompanied with straw and polyethylene mulches and this can save irrigation water in olive orchards.
