The hyperspectral reflectances of the canopy, the sword leaf, the third unfolding leaf from the top and ear of the main stem of two varieties of rice are measured by a ASD FieldSpec Pro FR in field and indoor under 3 nitrogen support levels in mature process. The concentrations of chlorophyll and carotenoid of leaves and ears corresponding to the spectra were determined by biochemical method. The spectral differences are significant for the canopy and leaves of rice under differet nitrogen support level, and the concentrations of chlorophyll and carotenoid of leaves increase with the increasing of nitrogen applying. There exist significant differences for the pigment concentrations of the leaves of rice under different nitrogen levels. The spectral reflectances of the canopy are gradually getting bigger in the visible region and smaller in the near infrared region as the growth stage goes on. 'Blue shift' phenomena for the spectra red edge position of the canopy, leaves and ears were proved. The concentrations of chlorophyll and carotenoid of leaves and ears are very significantly correlative to the spectral vegetation indices VI1(= R990/R553), VI2(=R1200/R553), VI3(=R750/R553), VI4(=R670/R440), VI5(= R553/R670), PRVI(=R800/R553), PSSRa, PSNDa and λred (the red edge position). The results show that these VIs can be used to estimate the concentrations of chlorophyll and carotenoid of leaves and ears of rice.
The Relationships between Narrow Band Normalized Vegetation Index and Rice Agronomics Variables are reported in this paper. The data for this study comes from ground-level hyperspectral reflectance measurements of rice at different stage of 2002 growing period. Reflectance was measured in discrete narrow bands between 350 and 2500 nm. Observed rice agronomics variables included wet biomass, leaf area index. Narrow band normalized difference vegetation index (NBNDVI) involving all possible two-band combinations of discrete channels was tested. Special narrow band lambda (λ1) versus lambda (λ2) plots of R2 values illustrates the most effective wavelength combinations (λ1 and λ2) and band-width (Δλ1 and Δλ2) for predicting rice agronomics variables at different development stage. The best of the NBNDVI models explained 53% to 83% variability rice agronomics variables at different development stage. A strong relationship with rice agronomics variables is located in red-edge, 700 nm to 750 nm, the longer portion of red, 650 nm to 700 nm, moisture-sensitive NIR, 950 nm to 1000 nm, longer portion of the blue band, 450 nm to 500 nm, longer portion of the green, 550 nm to 600 nm, the intermediate portion of SWIR, 1600 nm to 1700 nm, and the longer portion of SWIR, 2150 nm to 2250 nm.
The hyperspectral reflectance of the canopy in field, the first and the third unfold leaves from the top of corn are measured indoor in different stages by a ASD FieldSpec Pro FR. The concentrations of chlorophyll and carotenoid of leaves corresponding to the spectra are determined by biochemical method. The correlation between the pigment concentrations, leaf area indices, above ground biomass and fresh leaf mass and the red edge parameters of corn are analyzed. The hyperspectral reflectance are gradually getting smaller in the visible region and bigger in the near infrared region along with growth. The difference of reflectance between in the near infrared region and in the visible region is the biggest in flowering stage. There are “two peak” phenomena for the red edge of canopy spectra of corn. These phenomena are first the clearer with growth, then the clearest in flowering stage and after that are gradually weaken. The position of red edge (λred) of canopy spectra are between 710nm and 740nm. There are "red shift’ phenomena for λred before flowering stage, the slope of red edge (Dλred) and the area of red edge (Sred) before the elongation stage, but are gradually smaller and "blue shift’ after flowering stage for the slope of red edge (Dλred) and the area of red edge (Sred) of the canopy spectra. The leaf area indices (LAI), above ground fresh biomass, above ground dry biomass and fresh leaf mass are very significantly correlative to the red edge parameters λred, Dλred and Sred of the canopy spectra, and the concentrations of chlorophyll-a, chlorophyll-b, total chlorophyll and carotenoid of leaves also significantly correlative to their red edge parameters λred and Dλred. These prove that the red edge parameters (λred, Dλred and Sred) can be used to estimate LAI, above ground biomass and fresh leaf mass. The parameters λred and Dλred can be used to estimate the concentrations chlorophyll and carotenoid of leaves for corn.