[Quantitative relationships between leaf total nitrogen concentration and canopy reflectance spectra of rice]

By the method of statistics, this paper approached the quantitative relationships between leaf total nitrogen concentration (LNC) and canopy reflectance spectra of rice, based on the data from 5-year field experiments involving different varieties and nitrogen fertilization rates. The results showed that the LNC had higher correlations with the key spectral parameters of two bands than of single band. The relative, differential, and normalized difference vegetation indices (RVI, DVI, NDVI) of the bands in near infrared (760-1,220 nm) and visible light 510 nm, 560 nm, 680 nm and 710 nm all showed significantly positive correlations to LNC, and NDVI showed the best. All the parameters having significant correlations with LNC were selected to compare the R2 and SE in the regression equations with LNC, which confirmed that the NDVI of R1220 and R710 was the best parameter for predicting the LNC. The quantitative equation LNC = 3.2708 x NDVI (1220, 710) + 0.8654 was tested by the data from other three field experiments with different rice cultivars, water conditions and nitrogen fertilization rates, and the estimated R2, slope, and RMSE were ranged in 0.674-0.862, 0.908-1.010 and 11.315%-19.491%, respectively, indicating a good fit between the predicted and observed values of LNCs, which suggested that this model was feasible for predicting the LNC of rice under different cultivation conditions.