Comparison of Measured and Estimated Evapotranspiration of Pomegranate Grown Under Mediterranean Conditions

Due to the climatic changes and the decreasing water resources, it is very important to determine the correct crop water requirement and schedule an appropriate irrigation. FAO methodology based on reference evapotranspiration (ETo) and crop coefficients (kc) is widely used all over the world to determine crop water requirement. For many of the economically important plants, the kc coefficients have been determined. In contrast, many equations have been developed at different levels of detail to determine ETo. For this reason, it is essential to choose the most suitable ETo equation for a region and a plant. The aim of this study is to determine the crop water requirement (ETc) of the pomegranate using eleven different ETo equations (ASCE-StPM, FAO-56PM, 1972-KPen, 1948-Pen, FAO-24Pn, Prs-Tylr, 1957-Makk, 1961-Turc, FAO-24Rd, FAO-24BC and 1985-Harg) based on climatic data and to compare them with the measured crop evapotranspiration (ETc) value. To determine the best estimation equation of ETo, some performance criteria were used including coefficient of determination (R2), root mean square error (RMSE), relative error (RE), mean bias error (MBE), the Willmott index of agreement (d). According to the obtained results of the study, it was determined that the combination based and temperature based methods overestimated the crop water use. The best results were obtained using radiation-based equations. Makkink model (1957-Makk) was the best ETo equation for pomegranate grown in the Antalya region