Partitioning of net radiation and evapotranspiration over a superintensive drip-irrigated olive orchard

Abstract

To evaluate the partitioning of net radiation (Rn) and actual evapotranspiration (ETa), measurements of Rn, sensible heat flux (H), soil heat flux (G), latent heat flux (LE), reference evapotranspiration (ETo), transpiration (Tp) and soil evaporation (Es) were taken during the 2009/2010 and 2010/2011 growing seasons on a flat and uniform olive (cv. Arbequina) orchard, located in the Pencahue Valley, Region del Maule, Chile (35°23′ LS; 71°44′ LW; 96 m above sea level). Olive trees were trained on a triangular hedgerow system with a plant density of 1333 trees ha−1 (superintensive). An eddy covariance system, sapflow sensors and microlysimeter were used to measure ETa, Tp and Es, respectively. Results indicated that the eddy covariance measurements showed a lack of the energy balance closure of 12.8 %. Values of LE, H and G were between 28–47, 34–68 and 2–6 % of Rn, respectively, while ratios of Tp and Es to ETa ranged between 0.64–0.74 and 0.26–0.36, respectively. During two growing seasons, the single crop coefficient (Kc = ETa/ETo) was between 0.27 and 0.66, while the dual crop coefficient (Tp/ETo + Es/ETo) ranged between 0.26 and 0.56. According to these results, H and Tp were the main component of Rn and ETa, respectively, for the particular conditions of the drip-irrigated olive orchard with a fractional cover of 30 % and wetted area of 4.5 %.