Monitoring the ratio of leaf carbon to nitrogen in winter wheat with hyperspectral measurements

摘要

In crop leaves the ratio of carbon to nitrogen (C/N), defined as ratio of LCC (leaf carbon concentration) to LNC (leaf nitrogen concentration), is a good indicator that can synthetically evaluate the balance of carbon and nitrogen, nutrient status in crop plants. Hence it is very important how to monitor changes of leaf C/N effectively and in real time for nutrient diagnosis and growing management of crops in fields. In consideration of the close relationships between chlorophyll, nitrogen (N) and C/N, some typical indices aimed at N estimation were tested to estimate leaf C/N in winter wheat as well as several indices aimed chlorophyll evaluation. The multi-temporal hyperspectral data from the flag-leaf, anthesis, filling, and milk-ripe stages were obtained to calculate these selected spectral indices for evaluating C/N in winter wheat. The results showed that some tested indices such as MCARI/OSAVI2, MTCI and Rep-Le had the better performance of estimating C/N. In addition, GRA (gray relational analysis) and Branch-and-Bound method were also used along with spectral indices sensitive to C/N for improving the accuracy of monitoring C/N in winter wheat, and obtained the better results with R~2 of 0.74, RMSE of 0.991. It indicates that monitoring of leaf C/N in winter wheat with hyperspectral reflectance measurements appears very potential.