Monitoring Nitrogen Status And Grain Quality With Canopy Reflectance Spectra In Wheat

Remote sensing technology could be easily used to monitor and forecast growth characters, nitrogen status, yield and quality formation of crop plants, thus it was very important to the development of information agriculture. Based on the technology of canopy reflectance spectral and the test of agronomy parameters and physico-chemical index, the characteristics of canopy multispectral and hyperspectral reflectance under different conditions and their correlation to growth characters, nitrogen status and grain quality traits in wheat were analyzed in this paper. The sensitive spectrum parameters and quantitative regression models of leaf area index, biomass, nitrogen status and grain quality traits were confirmed. Based on the spectral monitoring of plant nitrogen status and the quantitative relationships between nitrogen status, nitrogen transportation and grain protein index, the indirect approach predicting mature grain protein status with reflectance spectra was forwarded, which provided technical basis for crop growth and precise diagnosis.In this study, the combination of multispectral and hyperspectral spectrum device was first used to compare the variation patter of canopy reflectance under different nitrogen supply, growing stage and cultivar in wheat. Results showed hyperspectal remote sensing was more feasible for monitoring water condition in crop plants than multispectral remote sensing. Reflectance at near infrared reflected flat (750-1300nm) increased with increasing nitrogen supply, whereas reflectance at visible band decreased. Reflectance at visible light initially decreased and then increased with growth progress after jointing, with the lowest value appeared at booting. However, reflectance in near infrared had opposite trend, which initially increased and then decreased to the lowest from anthesis to maturity. The canopy reflectance also was different for different cultivars under same nitrogen rate, with significant change at near infrared bands. These results provide background information for monitoring of growth characters, nitrogen status and grain qualities with canopy reflectance spectra in wheat.Based on the change patterns of leaf area index and dry weight under different nitrogen supply with growth stages, correlations of LAI and dry weight of leaf and stem to canopy multispectral and hyperspectral reflectance and spectral parameters were investigated, and put forward sensitive spectral parameters and quantitative equation forecasting LAI and dry weight of leaf and stem in wheat. Multispectral vegetation index, such as RVI (810, 510) and...