Abstract

Accurate estimation of crop evapotranspiration (ETc) considering global warming is a key aspect to optimize water applica-tion, yield and fruit quality for sustainable blueberry production. This study quantifies daily crop ETC , diurnal dynamics of the surface energy balance (SEB) and the crop factor (CF) of a drip-irrigated blueberry (Vaccinium corymbosum) orchard field. CF is defined as the ratio of ETc and reference ET. ET(c )and the SEB were measured using an Eddy Covariance (EC) system every 30 min during four growing seasons. Results show maximum values of available energy, Net Radiation (Rn) minus soil heat flux (G), reached 18 MJ m(-2) d(-1), while that the sum of turbulent fluxes extended to 17 MJ m(-2) d(-1). Maximum values of latent heat ( .1,E ) normally occur on November-December from 10 to 11 MJ m(-2) d(-1). The correlation between Rn between crop rows and Rn above the crop canopy-soil surface was 0.73 during all growing seasons. G below the canopy represents 5% of Rn above the crop canopy-soil surface. During this study, ETc reached up to 5.0 mm d(-1) when ETA was 7 mm d(-1). Maximum ETc values occur during December. Weekly specific CF varied from 0.5 to 0.8 from October to March. CF showed no significant variation year to year suggesting that they could be used by farmers to better predict water demand and improve water use efficiency. To our knowledge, there are no previous studies at a field's scale documenting all components of the daily SEB and its diurnal dynamics over blueberry orchards.