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THE IMPORTANCE OF SAP FLOW MEASUREMENTS TO ESTIMATE ACTUAL WATER USE OF MESKI OLIVE TREES UNDER DIFFERENT IRRIGATION REGIMES IN TUNISIA
Author(s) -
Vandegehuchte Maurits W.,
Braham Mohamed,
Lemeur Raoul,
Steppe Kathy
Publication year - 2012
Publication title -
irrigation and drainage
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.421
H-Index - 38
eISSN - 1531-0361
pISSN - 1531-0353
DOI - 10.1002/ird.1670
Subject(s) - irrigation , evapotranspiration , olive trees , irrigation scheduling , olea , crop coefficient , deficit irrigation , water consumption , mathematics , hydrology (agriculture) , irrigation management , environmental science , agronomy , horticulture , environmental engineering , ecology , geotechnical engineering , biology , engineering
ABSTRACT Improvement in irrigation techniques has led to an expansion of the irrigated olive area in Tunisia and consequently a rise in agricultural water consumption. Here, the actual water use of Olea europaea L. ‘Meski’ as estimated by thermal dissipation probe measurements was compared for different irrigation regimes: three plots with irrigation doses based on Penman–Monteith crop evapotranspiration (ETc), 0.33 × ETc and the local grower's experience (about 0.6 × ETc), respectively. The scaling up of sap flux densities proved to be difficult given the azimuthal and radial sap flux density variability and the conductive surface area asymmetry. Moreover, natural thermal gradients may lead to inaccurate use of standard sap flow formulas. Depending on the manner of upscaling, differences in water use of more than 50 l day ‐1 per tree were obtained (up to 0.7 × ETc irrigation dose). Despite these difficulties, sap flow calculations seem crucial to accurately determine the water needs of the orchard under investigation, as they corresponded closely to the lowest irrigation dose which was considered sufficiently high as no significant differences in drought stress variables were detected between the plots. Therefore, irrigation based solely on ETc leads to wasting of water; hence, careful application of both meteorological and sap flow methods is desirable in irrigation scheduling. Copyright © 2012 John Wiley & Sons, Ltd.