Evaluation Of ORYZA2000 Model For Aerobic Rice And Studies On Optimization Of Irrigation

Evaluations of ORYZA2000 model for aerobic rice HD297 were studied by parameters' calibrations and validations based on 3 years field experiments from 2002 to 2004 conducted in Changping Experiment Station (40°02'N, 116°10'E, elevation 43m) of China Agriculture University in Beijing. And after that, ORYZA2000 rice model was used to analyze the relations between yield and water use of aerobic rice HD297, and to study on optimum irrigations of aerobic rice in Beijing area.Firstly, the experiment results of 2003 were used to do the calibrations to obtain the crop parameters of aerobic rice HD297, then the ORYZA2000 model were validated on simulating biomass, leaf area index and final yield of HD297 and soil water tension by using the experiment data of 2002 and 2004. In the validation, the following indices were selected: the slope (a), intercept (β), and adjusted coefficient of correlation (R~2) of the linear regression between simulated and measured values, the student's /-test of means assuming unequal variance P(t*), as well as the root mean square error (RMSE) and the normalized root mean square error (NRMSE). The average of NRMSE of the simulations of total biomass above ground, green leaf biomass, stem biomass, panicle biomass, LAI and final yield for the two years is respectively 29.5%, 33.5%, 35%, 30%, 46% and 14%. Simulated soil water tensions fit well with measured soil water tensions. So, the evaluation results has showed that the ORYZA20000 model is sufficiently good to simulate the growth and development and final yield of HD297 as well as soil water tension, only with a little higher simulation errors of LAI.Analysis of yield and water use of HD297 in Beijing were done based on the daily meteorology data from 1971 to 2000 by the ORYZA2000 model which has been evaluated, and the results show that the average potential yield of 30 years is 8573 kg/hm2, and the average rainfed yield of 30 years is 4083.6kg/hm~2. Average maximum water requirement for the whole growth season is 712.7mm, but the rainfall of growth season in different years varies largely and there is 50% years in which water shortage reaches as much as 30%. Irrigation water requirement in the growth season varies form 150 to 400mm in different years. Meanwhile, the analysis proves that water use efficiency can be kept at the higher levels if irrigation water was given when relative soil wtater content was at the level of 60~70%.Also, the optimum irrigation schemes for different years from 1971 to 2000 were analyzed aimed at three yield level, 70%, 80% and 90% of potential yield. For the 70% of potential yield level, there are 23.3% of all years in which the rainfed yield can reach this level without irrigations, the maximum irrigalion water requirement in other years is 300mm, but in 53.3% years it is below 200mm. The irrigation water use efficiencies for the 70% potential yield level are between 1.44 g/kg and 15.21 g/kg. For the 80% of potential yield level, in all years there must be irrigations to reach this yield level, the maximum irrigation water requirement is 350mm, and the irrigation water use efficiencies is between 1.5 g/kg and 16.19g/kg. And for the 90% of potential yield level, the maximum irrigation water requirement is 600mm, and the irrigation water use efficiencies are between 1.04 g/kg and 7.30g/kg.