The CERES-Rice model

The CERES-Rice model is one of the crop models in the Decision Support System for Agrotechnology Transfer (DSSAT) family (Version 4.6) (Jones et al., 2003). The model simulates rice phenology development based on the GDDs calculated with the daily average temperature. Photosynthetic production accumulation and allocation to each organ are associated with the growth stage and the stress factors, such as temperature, CO₂, nitrogen, and water. In this study, no nitrogen or water stress existed during the rice growth period, and temperature and CO₂ were the main factors affecting photosynthesis. In the CERES-Rice model, the optimal DT for rice photosynthesis is set at 26 ° C (Singh & Padilla, 1995). A quadratic equation is used to calculate the temperature reduction factor (PRFT) that affects photosynthesis (Ritchie et al., 1998):

PRFT is applied to the calculation of photosynthetic production in the CERES-Rice model. When PRFT is equal to 1.0, this indicates no temperature stress on photosynthesis, and when it is equal to 0.0, there is the maximum temperature stress. The effects of CO₂ concentration on rice photosynthesis are also taken into account in the CERES-Rice model (Peart et al., 1988). A factor (PCO2) representing these effects was applied to the calculation of photosynthetic production based on Table 3. In this lookup table, the PCO2 value and corresponding CO₂ concentration are prescribed in the model based on Peart et al. (1988). The PCO2 value of any given CO₂ concentration was calculated with a linear interpolation between the two nearest factors whose weights were computed according to the given and two corresponding CO₂ concentrations.