Characteristics of Canopy Hyperspectral Reflectance and Changes of Red Edge Parameters under Different Nitrogen Levels

Using four wheat cultivars as materials, canopy spectral information under different nitrogen levels was studied. The agronomy components associated with red edge parameters were analyzed for quickly, acurately monitoring growth and nutritional status of wheat. The results showed that the canopy reflectance were different for different cultivars and growth stages in the same amount of nitrogen. The change was more great at near infrared bands than that of the visible lights. Reflectance at near infrared band increased clearly with the increase of nitrogen supply, whereas reflectance at visible band decreased and appeared a curve with one peak. When increasing nitrogen supply, red edge and green peak position of canopy reflectance spectra moved to direction of long wavelength(red light) and short wavelength(blue light), respectively. The correlations between REP amplitude and agronomic components were better than those between the other red edge parameters and agronomic components. The correlations between Lo, Lwidth and agronomic components were significantly negative. The correlations between other red edge parameters and agronomic components were significantly positive. The regression equations between red amplitude and agronomic components were established. Red edge parameters can provide an important basis for agricultural production by remote sensing means.