Abstract:In order to evaluate the reliability and applicability of dual crop coefficient approach on calculating actual evapotranspiration and crop coefficient of fruit tree in the North China Plain, the evapotranspiration and crop coefficient of peach tree were measured by sap flow and water balance methods in an orchard of Beijing, China in 2012 and 2013, and the corresponding values were also calculated by dual crop coefficient approach. Experimental results showed that daily evapotranspiration rates calculated by dual crop coefficient approach and measured by sap flow and water balance methods were increased firstly and then decreased with time during peach tree growth period, and the calculated values had significantly positive correlation with those obtained by the twp measurement methods (R2>0.77** and R2>0.76**). The relative error of total actual evapotranspiration in the whole growth period calculated by dual crop coefficient approach was less than 4.5% compared with the measured values by sap flow and water balance methods, but the calculated soil evaporation was 59.5%~64.8% smaller than that measured by micro-lysimeter, and the calculated transpiration was 25.6%~26.0% greater than that measured by sap flow method. The crop coefficients obtained by dual crop coefficient approach, sap flow and water balance methods also showed a increasing trend firstly and then they were decreased with time during the growth period of peach tree, and the average values during the whole growth period were 0.90, 0.89, and 0.95, respectively, for dual crop coefficient approach, sap flow and water balance methods. By calculation and analyses on the ratio of root mean square error to the standard deviation of measured data (RSR) and the Nash—Sutcliffe efficiency (NSE), it can be concluded that dual crop coefficient approach is an effective method to calculate actual evapotranspiration and crop coefficient of peach tree under full irrigation in arid and semi-arid areas.
