Evaluating Semi-Quantitative Approach of the AquaCrop Model for Simulating Maize Response to Nitrogen Fertilizer

AquaCrop model determines the response of plant to degree of soil fertility stress by a simple and semiquantitative approach. The objective of this study was to evaluate this approach to simulate maize growth parameters under different nitrogen application in semi-arid environment of Iran. The experiment was conducted at the research farm of the College of Aburaihan, during two years (2015 and 2016) and without water stress. Five nitrogen (N) treatments were investigated including no nitrogen (N0), 50(N1), 10 (N2), 150(N3) and 200 kg N. ha-1 (N4) by Randomized Complete Block design with three replications for each year. Calibration was carried out using the data of N0 and N4 for 2015 and validation was performed with data of remaining treatments in 2015 and whole data of 2016. The accuracy of the model in calibration stage was tested using relative root-mean-square error (RRMSE), coefficient of determination (R2) and mean bias error (MBE), which were about 11.8%, 0.995 and 0.51 ton.ha-1 and 11.8%, 0.988, -1.02 ton.ha-1 for estimating biomass development in the N0 and N4 treatments, respectively. The RRMSE, R2 and MBE values for validation treatments were obtained as 19.06 %, 0.920, 0.92 ton.ha-1 for grain yield and 5.32%, 0.975, 0.41 ton.ha-1 for final biomass yield, respectively. The results show that calibrated model estimates soil water content and water productivity in different treatment accurately. Nevertheless, It is demonstrated that AquaCrop was not able to simulate development of biomass and CC precisely during growing season, but it is more accurate in estimating final biomass and grain yield.