Evapotranspiration predictions of CERES-Sorghum model in southern Italy

The purpose of this study was to modify and calibrate the CERES-Sorghum water balance model for the dry, high radiation and windy conditions in an area in Southern Italy. The equation for estimating potential evapotranspiration (E-0) was substituted by another one, calibrated in the study site and expressed as a function of equilibrium evaporation and maximum vapour pressure deficit (defined as the difference between the saturation vapour pressure at maximum and at minimum temperatures). To calibrate the E-0 equation included in CERES-Sorghum, two drainage lysimeters, located at the Istituto Sperimentale Agronomico experimental farm, Foggia (Italy), were used to measure weekly evapotranspiration of well-watered, irrigated fescue grass, from 1976 to 1986. A further drainage lysimeter, located in the same farm and cropped with well-watered grain sorghum (cv. NK 121) was used to calibrate the genetic coefficients input to the modified CERES-Sorghum model during the cropping seasons 1979 and 1980. Simulated phenological dates (anthesis and maturity), grain yield, LAI, biomass and crop evapotranspiration were then compared with the measured ones in a fourth drainage lysimeter cropped with sorghum. The modified model simulated grain yield accurately, but simulated daily evapotranspiration did not always match well the observed value, especially early in the crop cycle. Improvements are needed to the model in its simulation of soil evaporation and in the crop response function to temperature. (C) 1997 Elsevier Science B.V.