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Rice crop growth and yield in the north Iran are affected by crop duration and phenology.The purpose of this study was to calibrate and validate the ORYZA2000 model under potential production based on experimental data for simulating and quantifying the phenological development,crop duration and yield prediction of rice crop influenced by different seedling ages.In order to calibrate and validate the crop parameters of ORYZA2000 model,a two-year field experiment was conducted under potential growth condition for transplanted lowland rice during the 2008-2009 rice growing seasons,using three rice varieties with three seedling ages (17,24 and 33 days old).The results showed that the seedling age changed crop duration from 7 to 10 d.The ORYZA2000 model could predict well,but consistently underestimated the length of growing period.The range in normalized root mean square error (RMSEn) values for each phenological stage was between 4％ and 6％.From our evaluation,we concluded that ORYZA2000 was sufficiently accurate in simulation of yield,leaf area index (LAI) and biomass of crop organs over time.On average,RMSEn values were 13％-15％ for total biomass,18％ 21％ for green leaf biomass,17％-20％ for stem biomass,16％-23％ for panicle biomass and 24％-26％ for LAI.The RMSEn values for final yield and biomass were 12％-16％ and 6％-9％,respectively.Generally,the model simulated LAI,an exceeded measured value for younger seedlings,and best-fit was observed for older seedlings of short-duration varieties.The results revealed that the ORYZA2000 model can be applied as a supportive research tool for selecting the most appropriate strategies for rice yield improvement across the north Iran.