ESTIMATION OF WATER PRODUCTIVITY AND CALIBRATION AND VALIDATION OF THE CROPSYST MODEL FOR RICE UNDER NITROGEN AND IRRIGATION MANAGEMENT

Simulation of yield response to water and fertilizer plays a key role in improving the efficiency of agricultural water. In this regard, the purpose of this study is the calibrating and validating of the CropSyst model to evaluate the effect of nitrogen fertilization and irrigation on the growth of rice in the crop field at the Rasht Rice Research Institute between 2013 and 2014. Three irrigation treatments (continuous, around five and eight days) were considered as the main factors and the amount of nitrogen in four concentration (0, 90, 120, and 150 kg N ha(-1)) as a sub-factor. Based on the evaluation results it can be concluded that the CropSyst model, with the normalized root mean squared error (RMSEn) 7 and 15% with explanation factor, R-2 of 0.73-0.84 for simulating the rice grain yield, and also RMSEn 9 and 10%, R-2 of 0.77-0.82 for simulating the biological yield, had the appropriate accuracy of the simulations. According to RMSEn 1 and 0.8%, R-2 of 0.58-0.73 for simulating the leaf area index, suggested a moderate simulation. These results showed that a reasonable estimate of the model as the efficiency of a model for the grain yield, biological yield, and LAI were 0.87, 0.98, and 0.80, respectively. The results of the simulation based on the amount of transpiration water productivity for both years showed that treatment I3N2 and I3N3 had the highest amount. The amount of evaporation in irrigation water management two-year period only 39% of evapotranspiration is evaporated, While the amount of intermittent irrigation management 5 and 8 days, respectively, 35% and 32% respectively. These subjects simulations suggest that, given the good models and maximum data consistency, if management is aimed at maximizing the efficiency of water use can solve these models as a means to support the planning application.