Evaluation of yield and water productivity in rice under irrigation management and plant density with use ORYZA2000 model

In order to investigation of irrigation management and plant density effects on water productivity of rice, a field experiment was conducted in the Rice Research Institute of Iran (Rasht) during 2001 and 2002. The study was carried out in a split plot design with four different irrigation regimes as main plots and three plant densities as subplots. In this experiment, ORYZA2000 model was used to quantify water productivity, and water balance components of alternate for irrigation and plant density interactions in rice. Evaluation simulated and measured yield by adjusted coefficient of correlation; T test of means; and by absolute and normalized root mean square errors (RMSE). Results showed that the yield was simulated with an RMSE of 150–182 kg ha^-1 and a normalized RMSE of 6%. In order to model the various water productivity components, ORYZA2000 model was used. Using the actual yield and simulated water balance (ORYZA2000), the calculated average WPET was lower than the average WPT: 35%. The results showed that the irrigation by 75% evaporation from pan evaporation and 20cm×20cm plant density is the optimum irrigation method and crop density management.