Water use of a super high density olive orchard submitted to regulated deficit irrigation in Mediterranean environment over three contrasted years

Abstract

The measurement of transpiration at the field level is a challenging topic in crop water use research, particularly for orchards. The super high density olive orchard system is in great expansion all over the world, so these investigations are necessary to assess the trees water use under different irrigation techniques. Here, transpiration at plant and stand scales was measured using the sap flow thermal dissipation method, in an olive orchard (cv. “Arbosana”) subjected to full and regulated deficit irrigation (RDI) with a withholding irrigation period under Mediterranean climate (southern Italy). The measurement method was used after specific calibration and correction for wound effect, azimuthal and gradient errors. Water use efficiency (WUE) and water productivity (WP) were determined over three complete growth seasons (2019–2022). The seasons were submitted to highly contrasted weathers. Measurements of stem water potential and stomatal conductance showed that the RDI trees were under mild-moderate water stress only during the withholding irrigation period. Results showed that seasonal Tr was not significantly different in the two treatments in all seasons (249 and 267 kgm− 2, 249 and 262 kgm− 2, 231 and 202 kgm-2 for FI and RDI in the three seasons, respectively) and that WUE was greater in RDI treatment without any impact on yield. The main conclusion is that, when the available water in the soil is limited, olive trees decrease transpiration under any atmospheric conditions, but when the water in the soil is amply available, drought conditions lead to a decrease in tree transpiration.