Spectral reflectance of rice canopies with different nitrogen treatment was measured over an entire growing season and eight spectral indices such as RVI

NDVI

PVI etc were calculated. Based on the biological mechanism of yield formation

relationships of these vegetation indices to yield and its components were analyzed. The results showed that it was limited to predict yield with vegetation index from single or multiple developing stages. However

the dynamic curve of Leaf Area Nitrogen Index （product of LAI by leaf nitrogen content on dry weight basis） can well track the process of yield formation. Due to the close relationship with the vegetation index

Cumulative Leaf Area Nitrogen Index （CLANI

the area below the curve） was used to derive a model named VI-CLANI-Yield model for rice yield estimation. The comparison of the present model with the LAD-Yield model and complex VI-Yield model indicated that the yield estimation accuracy was best for VI-CLANI-Yield model with average relative error of 0.075. This suggests that VI-CLANI-Yield model would be a practical and effective approach for rice yield forecasting.