Rice yield was estimated at all the third mesh points in Japan for the condition of elevated CO2 concentration and increased temperature with a growth model. Growth parameters of the model for 36 principal Japanese japonica type varieties were employed for the calculation. In cases of the temperature change in -2, +2 and 4°C, decrease of the total yield of Japan was estimated to be about -14, -5 and -12%, respectively. Under the conditions with temperature increment of 2°C, only rice yield in Hokkaido rose. In central and southern part of Japan, rice yield decreased as the temperature rose, however, the reduction could be avoided by advancing the planting date.
Effect of CO2 concentration on rice yield was incorporated into the radiation use efficiency which was calculated from light-photosynthetic curves of canopies in growth chambers. Rice yields increased from 10 to 15% depending on the radiation intensity when CO2 concentration was elecated from 350ppm to 1200ppm. Under the lower the radiation intensity, the increase of rice yield caused by elevated CO2 concentration was higher.
