USE OF SAP FLOW SENSORS TO DETERMINE TRANSPIRATION OF A YOUNG DRIP-IRRIGATED OLIVE ORCHARD ('ARBEQUINA') UNDER SEMI-ARID CONDITIONS

In drip-irrigated olive orchards, tree transpiration (T) is the most important component of the actual evapotranspiration (ET_a) under semi-arid conditions. For this reason, the determination of T is a very important issue to apply a correct irrigation scheduling. Thus, the objectives of this study were to determine T, and to evaluate the relations of: i) T and ET_a, ii) T and solar radiation (SR), and iii) T and vapor pressure deficit (VPD). A field study was carried out to measure T and ET_a of a commercial super intensive hedgerow (5 m between rows and 1.3 m between plants) 3-year-old drip-irrigated olive orchard (Olea europaea L. ‘Arbequina’) located in Pencahue valley, Maule Region, Chile (35°23’LS; 71°44’LW; 96 m a.s.l.). Measurements of T and ET_a were done using sap flow (SF) sensors and an eddy correlation system (EC), respectively. The heat pulse velocity method (HPV) was used to obtain T every 30 min. The results show that the diurnal trend of T was similar to those of ET_a, VPD and SR for most of the study days. Also, on a daily basis, mean values of T under sunny days were around 2.6 L plant^-1 day^-1, which represent about 67% of total olive orchard water requirements.