Influence of irrigation regime on gas exchange, growth, and oil quality of field grown, Texas (USA) olive trees

Olive (Olea europaea L.) oil production is an emerging industry in Texas (USA). However, limited research has been conducted to determine best irrigation practices for Texas growers. In this study, established "Arbequina"olive trees from three south Texas orchard locations were used to investigate effects of irrigation volume on olive tree gas exchange, growth, and oil quality. Twelve-year-old trees were exposed to three irrigation regimes. Over the course of two growing seasons, leaf gas exchange, shoot growth, and oil quality were measured. Data from a single orchard and growing season are presented. Differences in monthly and overall leaf gas exchange data were not found. Based on soil surface area under each tree's dripline, depth of total water applied to each tree (irrigation plus precipitation) ranged from 1,451 (three-emitter irrigation treatment) to 759 mm (one-emitter irrigation treatment). Trees exposed to the three-emitter irrigation treatment produced the greatest shoot growth. Fruit mass and fruit volume were greatest for trees which had the fewest emitters (lowest irrigation volumes). Oil pressed from each experimental tree rendered extra virgin olive oil. Oil chemical analysis indicates total phenols tended to be greatest from trees receiving the least volume of irrigation. For Texas olive growers, research suggests there are opportunities to reduce irrigation, yet maintain olive oil quality.