Calibration and Evaluation of AquaCrop Model Under Different Irrigation Methods for Maize (Zea mays L.) in Central Region of Iraq

Abstract

AquaCrop simulation model is one of the most important models in the evaluation of irrigation management and the improvement of water use efficiency. This study aimed to test and simulate Aquacrop for maize with the Cropwat to calculate the evaporation under different irrigation methods. Experiments consisted in the use of furrow irrigation and drip irrigation surface (DI) and, sub-surface (SDI) for the depths (10, 20, and 30 cm). Three NPK treatments were used as subplots: 50N, 15P, 30 K kg ha−1, 100N, 30P, 60 K kg ha−1, 200N, 60P, 120 K kg ha−1. Field observations were carried out in 2016 and 2017 seasons to evaluate AquaCrop performance in simulating dry yield, harvest index, biomass, canopy cover, and water productivity. Statistics for root mean square error (RMSE), coefficient of determination (R2), index of agreement (d), coefficient of efficiency (E), mean bias error (MBE) suggest that the model prediction is good. The values of the (RMSE) statistics were (20.6%, 2.5%, 2.1%, 15.9%, and 18.4%) for biomass and (0.8%, 2.2%, 3.4%, 22.9%, and 1.6%) for dry yield and the harvest index (12.5%, 9.9%, 3.1%, 6.2%, and 9.2%) and for water productivity. The 2016 season results were higher than those of the 2017 season. The values were (29.4%, 5.6%, 34.5, 20%, and 68%). The canopy cover results ranged between (23. to 96.7) and (23.2 to 97.7) for 2016 and 2017, respectively. The crop coefficient Kc was calculated, and the results ranged between (0.25 to 1.42) for the 2016 season and (0.27 to 1.67) for the 2017 season, for the irrigation treatments and according to the plants growth stages. In central Iraq, AquaCrop can be used reliably to test the efficacy of the proposed irrigation management strategies for maize.