Abstract: Based on the three principles related to the optimum growth season, i. e. , (1) matching with crops for rotation, (2) maximizing the yield and, (3) minimizing the endangerments, the authors computed the optimum growth seasons and their corresponding photosynthetic yields for 4 rico varietal types in the Yangtze River Valley, by using the established model, i. e. , the "rice clock" model for rice development, the models for estimating optimum leaf area index and the photosynthetic production.

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