Action of derivative spectra and vegetation indices for rice

The hyperspectral reflectances of the canopy of two varieties of rice were measured by an ASD FieldSpec Pro VNIR^TM and an ASD FieldSpec Pro FR^TM in field under different nitrogen levels at different stages in two years. The concentrations of chlorophyll and carotenoid of canopies corresponding to the spectra were determined by biochemical method. The action of derivative spectra on eliminating background influence on rice canopy spectra and that of vegetation indices on determining agricultural parameters were analyzed. The result shows that the position and slope of red edge of canopy spectral reflectance of rice are certainly correlative to fractional vegetation cover and nitrogen supply level. The leaf area indices, above ground fresh biomass, above ground dry biomass, the concentrations of chlorophyll-a, chlorophyll-b, total chlorophyll and carotenoid of canopies are significantly correlative to the position of red edge and slope of red edge of the canopy spectra. The multiple spectral vegetation indices RVI and NDVI of rice canopy are very significantly correlative to LAI and above ground matter, but the hyperspectral vegetation index and its variable are certainly correlative to rice fractional cover, nitrogen supply level, leaf area indices, above ground fresh biomass, above ground dry biomass, the concentrations of chlorophyll and carotenoid of canopies. This proves that it is feasible to use the technology of derivative spectrum and the method of vegetation index to monitor the pigment concentration and growth of rice.