Hyperspectral Estimation Technique of Plant Nitrogen Content of Alfalfa Spectral reflectance characteristics of summer maize under long-term fertilization Plant nitrogen content of annual ryegrass and spectral reflectance response to nitrogen application level Response of Canopy Spectral on Chlorophyll Content of Winter Wheat under Different Sowing Date Estimation of tobacco leaf area index and aboveground biomass using canopy spectra Red edge parameters of winter wheat canopy under different nitrogen levels Red-edge characteristics of winter wheat canopy spectra Monitoring Grain Protein Accumulation Dynamics with Canopy Reflectance Spectra in Wheat