Estimation of Plant Nitrogen Concentration in paddy rice from field canopy spectra

Remote sensing techniques can provide quantitative information on vegetation conditions Such as Leaf Area Index and Nitrogen concentration. In this work we evaluate the potentiality of radiometric measurements for the prediction of rice Plant Nitrogen Concentration (PNC): we tested all possible wavelength combinations in the visible/Shortwave infrared region of the spectrum to derive a Normalized Difference Index (NDI) correlated to PNC. The NDI (lambda(1)=503 nm, lambda(2)=483 nm) was compared to traditional indices and found to perform better and to be least affected by structural parameters (LAI and biomass). An empirical NDI-PNC model was calibrated and validated with independent data (R(2)=0.53).