Sorghum and sunflower evapotranspiration and yield from simulated leaf area index

Accurate prediction of evapotranspiration and crop yield is essential for good water management. This paper describes the structure and testing of PILOTE 1.3, an operative water balance model which predicts actual evapotranspiration (AET) and yield of crops. The model simulates the LAI, leaf area index, using a water stress index and thermal time which is calculated from air temperature. A previous model PILOTE 1.2 described by [Mailhol, J.C., Ruelle, P., Revol, P., 1996a. PILOTE: Un modele operationnel pour deceler 1'apparition du stress hydrique. 16th International Congress on Irrigation and Drainage (ICID-CIID). 47th International Executive Council Meeting. Workshop on Crop-Water-Environment Models. Cairo International Conference Centre Cairo-Egypt, September 17, 1996. 15–22 Sept. 1996. pp. 209–222; Mailhol, J.C., Ruelle, P., Revol, P., Delage, L., Lescot, J.M., 1996b. Operative Modelling for Actual Evapotranspiration Assessment: Calibration Methodology. ASAE Proceeding of ASAE. San Antonio, TX, 3–7 Nov., 1996. pp. 474–479] is used as a sub-model and calculates the water stress index. The simulated LAI values generate crop coefficients corresponding to actual local conditions. Data obtained from field experiments carried out at Montpellier (FRANCE) on sorghum ( Sorghum bicolor (L.) Moench) in 1990 and 1992, and on sunflower ( Helianthus annuus L.) in 1994 and 1995 were used for the model calibration. When tested against independent data the model generates reliable predictions of actual evapotranspiration and yields of sorghum and sunflower ( r 2 > 0.93).