Assessment of different reference evapotranspiration models to estimate the actual evapotranspiration of corn

In this study, an experiment was performed to assess and rank different evapotranspiration models. This was done to estimate the daily actual evapotranspiration of corn using a single (K.sub.c-single) and dual (K.sub.c-dual) crop coefficients in the semiarid climate of Karaj, Iran, in 2014. Daily evapotranspiration calculations using one combination-based model, one pan evaporation-based model, nine temperature-based models, ten radiation-based models, and seven mass transfer-based models were compared to the lysimeter measurements. Considering the single-crop coefficient, the Hargreaves-M3 model (RMSE = 1.89 mm/day) in the temperature-based models, the Caprio (1974 (See CR12)) model (RMSE = 1.99 mm/day) in the radiation-based models, and the Albrecht (1950 (See CR2)) model (RMSE = 4.33 mm/day) in the mass transfer-based models were ranked first place. Moreover, the Hargreaves-M2 model (RMSE = 0.88 mm/day) in the temperature-based models, the Caprio (1974 (See CR12)) model (RMSE = 1.17 mm/day) in the radiation-based models, as well as the Albrecht (1950 (See CR2)) model (RMSE = 3.76 mm/day) in the mass transfer-based models using the dual-crop coefficient, provided the most accurate estimation of daily corn evapotranspiration as compared to the lysimeter measurements.