[Estimation of nitrogen concentration in cotton leaf based on canopy reflectance spectra]

Through analyzing the relationships of nitrogen concentration in cotton leaf under different nitrogen supply levels with canopy multi-spectral reflectance and its derived ratio vegetation index (RVI, rholambda1/rholambda2), normalized difference vegetation index (NDVI, (rho(lambda1) - rho(lambda2))/(rho(lambda1)) + rho(lambda2)) and differential vegetation index (DVI, rho(lambda1) - rho(lambda2)), the sensitive wave bands and prediction functions of cotton leaf nitrogen concentration were worked out. The vegetation index composed of visible region (610, 660, 680 and 710 nm) and near infrared region (760, 810, 870, 950, 1 100 and 1 220 nm) had a higher correlation with the nitrogen concentration in cotton leaf, and the RVI composed of 950 nm and 710 nm could best predict the leaf nitrogen concentration. The validation with independent field experimental data indicated that RVI (950 nm and 710 nm) -based model was suitable for estimation of leaf nitrogen concentration of different cotton cultivars at their different growth stages.