Transpiration by Sap Flow Thermal Dissipation Method: Applicability to a Hedgerow Olive Orchard

The climate change requires thrifty use of water resources in agriculture since irrigation is became common also for those crops like olive orchard that were traditionally grown in rainfed conditions. The water requirement is imperative in semi-arid conditions of the Mediterranean basin especially if the olive orchards are cultivated in super high density. For a correct irrigation scheduling, methods to measure transpiration (Tr) at plant level are used. Among the most spread methods to determine Tr, the thermal dissipation method (TDM) has been applied on a hedgerow olive orchard considering: (i) species-specific local calibration, (ii) wound effects, (iii) azimuth correction, and (iv) radial gradient corrections. The performances of the corrected TDM method have been evaluated with respect an independent method, the water balance at weekly scale. If any correction nor specific calibration is carried out, the underestimation of the actual transpiration calculated by TDM was of about -18% with respect to the water balance method.