Aquacrop Model Evaluation in Maize Under Different Water Availabilities in the Western of Uruguay

Author(s): Luis Gimenez

FAO’s Aquacrop (AQ) crop growth and productivity model was evaluated using four water management experiments in maize during 2009, 2010, 2011 and 2012 seasons. Model was calibrated in a hydrological crop comfort situation, based on observations of Canopy Cover (CC), Biomass (B) and Yield (Y). Firstly, proposed default parameters were used and then Canopy Growth Coefficient (CGC), Canopy Decline Coefficient (CDC) and normalized Water Productivity (WP*) were adjusted. Calibration results allowed adjusted B and Y simulations. Values for B and Yobtained from statistical indicators used were, respectively: root mean square error (RMSE) = 2085 and 841 kg ha-1, Normalized Root Mean Square Error (NRMSE) = 8.7 and 6.9%, Willmott’s “d” = 0.96 and 0.93 and Mean Absolute Error (MAE) = 1568 and 762 kg ha-1. Results permitted to conclude that AQ simulated well both variables. Afterwards, with calibrated parameters, model was validated in crop water deficiencies and rainfed situations. Results showed greater differences between observed and simulated values. In case of water deficiencies caused around flowering, during grain filling, and accumulated in the vegetative stage plus around flowering, the model simulated both variables with errors. In rainfed crops and hydrologically different seasons, AQ estimated well B and Y when rains were abundant, and crop presented no water deficiencies. In contrast, in seasons with severe water stress in certain crop cycle stages, alternating with water comfort periods, model estimated with errors B and Y. Results suggest that in water deficiencies situations, AQ stress coefficients require adjustments in corn crops.