Water use and root zone water dynamics of drip-irrigated olive (Olea europaea L.) under different soil water regimes

A field experiment was conducted over 2 years in a semiarid region of Australia to determine the root water uptake-soil water regime relationship and water use of drip-irrigated olive (Olea europaea L.) (cv. Corregiolo). A soil water balance approach was used to estimate the olive trees' water use. Olive evapotranspiration during the first ('on') year was 620, 685 and 723 mm for rainfed (during pit-hardening period), deficit (during pit-hardening period) and irrigated treatments, respectively. These values were 555, 610 and 673 mm during the second ('off') year. Soil water monitoring in three dimensions was used to infer vertical and lateral root distribution and root activity. The soil water depletion pattern indicated that most of the roots were in the top 60 cm soil depth and aligned along the tree rows. This information is important for fertilizer application and for the placement of drip laterals and soil water measurement equipment used for irrigation scheduling. It also underscores the importance of using three-dimensional models to understand root zone hydrology of drip-irrigated trees.