Characterizing Canopy Hyperspectral and Multispectral Reflectance under Different N-application Conditions in Wheat

The change of canopy spectral reflectance under different cultivars,different growth stages and varied nitrogen rates were investigated by characterizing canopy multispectral and hyperspectral reflectance in wheat.The results showed that the canopy reflectance differed with cultivars,with significant change at near infrared bands.Reflectance at visible light initially decreased and then increased with growth progress after jointing,with the lowest value appeared at booting.Reflectance increased and reflectance peak also disappeared gradually in course of leaf yellowing.However,reflectance in near infrared had opposite trend,which initially increased and then decreased to the lowest from anthesis to maturity.Reflectance at near infrared reflected flat(750~1300 nm)increased with increasing nitrogen supply,whereas reflectance at visible band decreased,and green peak and red edge position of canopy reflectance spectra also moved to direction of blue light(short wavelength) and red light(long wavelength),respectively.These results provide background information for monitoring of growth characters and nitrogen status with canopy reflectance spectra in wheat.