Parameterization and evaluation of APSIM-Wheat model for winter wheat : Application of model under climate change

The present research has been conducted to parameterize and evaluate the APSIM-Wheat model for winter wheat and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar winter wheat in Karaj and Khomein regions between 2014 and 2015, under four irrigation regimes and three levels of nitrogen fertilizers. The experiments have been conducted in both regions as split-plot in a randomized complete block design. Irrigation is considered as main plot and nitrogen as a sub-plot. Model parameterization is based on observational data from full irrigation and 200 kg/ha nitrogen treatment in both regions. Results from the model evaluation show that the simulated values closely predict the observed values so that the RMSE in both regions is less than 670 and 450 kg/ha for biomass and yield, respectively, being below 0.56 for leaf area index as well. Normalized RMSE in all treatments has been below 17.8%, with Wilmot's index being above 0.82. The evaluation of model shows high performance and its possible use in other studies. Results from climate change analysis show that increasing the temperature from 0 to 5 °C leads to a maximum reduction of 75% in grain yield and an increase in carbon dioxide concentration, resulting in a maximum increase of 24% and, if the temperature increase exceeds three degrees Celsius, the grain yield will decrease in all possible concentrations of carbon dioxide.