Comparing aquaCrop and cropSyst models in simulating barley growth and yield under different water and nitrogen regimes: Does calibration year influence the performance of crop growth models?

tThis work investigated the performance of AquaCrop and CropSyst in simulating barley growth underthree water treatments (full irrigation, 50% irrigation and rainfed) and two nitrogen levels (high andlow) with a particular attention to the influence of calibration year on the modelling results. Three years(2006-2008) of data from the experimental work carried out in Southern Italy were used. The modelswere calibrated for each of three years and then validated for two other years. The overall results pointedout that both models could be calibrated with data of one of any the three years and validated withall other data. Nevertheless, errors of estimate slightly changed in respect to the year of calibration andwere sensitive, from one year to another, to weather conditions and different water and nitrogen regimes.The results indicated AquaCrop superior than CropSyst when the calibration was done on the basis of2006 and 2008 data, whereas the models performed in a similar way when the calibration was done for2007. In the case of final biomass, the relative RMSE was lower for AquaCrop (from 0.09 to 0.15) than forCropSyst (from 0.15 to 0.17). Similarly, in the case of final yield, the relative RMSE of AquaCrop was lower(from 0.11 to 0.17) than that of CropSyst (from 0.16 to 0.23). AquaCrop overestimated final biomass by0.18 and 0.27 t ha-1for 2006 and 2008 calibration year, respectively, and underestimated biomass by1.02 t ha-1when calibration was done on 2007 data. CropSyst underestimated biomass independentlyon the calibration year, from 0.83 to 1.26 t ha-1.