Irrigation practices and fruit yields of olives in southern Australia

Availability of irrigation water is a main impediment to olive production in Australia, where there is a dearth of well-defined recommendations on water management for a viable industry. To develop irrigation guidelines, a good understanding of existing water management practices and associated yield outcomes are needed. This study evaluated water management and water-use in a range of four groves, including a rainfed grove, over two seasons in South Australia. Seasonal water input ranged from 206 to 617 mm (2.1 - 6.2 ML/ha), with irrigation accounting for about 70% in high yielding groves. Irrigation increased the proportion of seasonal evapotranspiration (ET), which averaged between 267 and 617 mm, partitioned through transpiration by up to 3-fold when compared to the rainfed grove. All groves experienced some degree of water deficit during the critical mid-season (December - February) when the crop factors (Kc) observed were up to 30% lower than estimated optimum level, which could be up to 0.70. A change to drip irrigation technology from full-cover sprinkler system would save up to 200 mm of water in an average season. The quantity of fresh fruits produced per unit of ET ranged from 3.2 to 32.1 kg ha⁻¹ mm⁻¹, and was between 7.2 and 49 kg ha⁻¹ mm⁻¹ when based on transpiration. Reasons for the differences in yield outcomes are discussed in relation to water management.