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 standard (SI) 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 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, otherwise the two treatments were under the same good water conditions. Following these small water differences between treatments, results showed that seasonal transpiration (E_p) was not significantly different in the two treatments in all seasons (249 and 267 mm, 249 and 262 mm, 231 and 202 mm for SI 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, high atmospheric demand conditions lead to a decrease in tree transpiration.

田间蒸腾测量是作物用水研究中的一个具有挑战性的课题，特别是对于果园。超高密度橄榄园系统正在世界各地大规模扩张，因此有必要进行这些调查来评估不同灌溉技术下树木的用水情况。这里，在地中海气候下进行标准（SI）和调节赤字灌溉（RDI）并在暂停灌溉期间的橄榄园（cv.“ Arbosana ”）中，使用液流热耗散法测量了植物和林分尺度的蒸腾作用（意大利南部）。该测量方法是在针对伤口效应、方位角和梯度误差进行具体校准和校正后使用的。水分利用效率（WUE）和水生产率是在三个完整的生长季节（2019-2022）确定的。季节变化呈现出强烈反差的天气。茎水势和气孔导度的测量表明，RDI树仅在停灌期间处于轻-中度水分胁迫下，其他处理均处于相同的良好水分条件。根据处理之间这些微小的水分差异，结果表明，两个处理在所有季节中的季节性蒸腾量（E p ）没有显着差异（三个处理中 SI 和 RDI 分别为 249 和 267 毫米、249 和 262 毫米、231 和 202毫米_）季节，分别），并且 RDI 处理的 WUE 更高，但对产量没有任何影响。主要结论是，当土壤中的可用水有限时，橄榄树在任何大气条件下都会减少蒸腾量，但当土壤中的水充足时，高大气需求条件会导致树木蒸腾量减少。