SUMMARY
The search for decision-making tools is essential in order to control agricultural practices and plan for sustainable agriculture that respects the environment. To this end, FAO has developed an evaluation model called AquaCrop, which covers most technical routes, including fertilization. In this perspective, this study focuses on the AquaCrop model (v6.1) to calibrate it for the simulation of lettuce crop yields (Lactuca sativa L), under different fertilization levels for the trial periods (2015/2016) and (2016/2017). Four levels of fertilization were examined under rain conditions, namely T1 (0 kg N/ha), T2 (60 kg N/ha), T3 (120 kg N/ha) and T4 (180 kg N/ha). The model performance was evaluated using the coefficient of determination (R2), the square root of the standard mean square error (nRMSE) and the Willmott agreement index (d). The model calibration gave 0.64 < R2 > 0.98; 18 < nRMSE > 46.3; 0.78 < d > 0.96 by simulating canopy coverage and dry biomass. While, the validation gave 0.81 < R2 > 0.98; 5.6 < nRMSE > 25.7; 0.93 < d > 1 by simulating canopy and dry biomass coverage. During calibration and validation, the prediction error for the yield ranged from 11.55 to 11.78% and from 9.54 to 12.72%, respectively, indicating good model performance. Based on yield and dry biomass, the T3 treatment (120 kg N/ha) gave a better yield compared to other treatments, which was demonstrated by both experimental results and model simulations. These results show that the AquaCrop model could be recommended as a practical tool to better manage fertilization where its performance is poor.