Abstract: The optimum temporal for rice estimation using remote sensing data included the optimum temporal for rice planting area estimation and the optimum temporal for rice yield estimation. Based on GIS,the rice potential planting area was extracted. Therefore, the study area became smaller and the plant species considered decreased. So the optimum temporal for rice planting area estimation were determined through comparing the crop phonological calendars. In order to select the optimum temporal for rice yield estimation using remote sensing data,the relationships between the rice yield and agronomic parameters,the agronomic parameters and spectral variables,the rice yield and spectral variables for different development stages using field experiment data in1989 and 1990 were studied. The result showed that the key period of rice production was from boot stage to heading stage. At last,the optimum temporal for rice yield estimation using remote sensing data was selected using the rice phenological calendars of 1998.

Key words: Rice, Remote sensing, Optimum temporal, NBPT, urease inhibition rate, NPPT, urea, soil texture, urease inhibitors