A New Method to Determine Central Wavelength and Optimal Bandwidth for Predicting Plant Nitrogen Uptake in Wheat.

Abstract: Plant N uptake is a good indicator of crop nitrogen status. In this study, a new method was designed to determine the central wavelength, optimal bandwidth and vegetation indices for predicting plant N uptake (g N m-2) in wheat (Triticum aestivum L.). The data were collected from the ground-based hyperspectral reflectance measurements in eight field experiments on wheat of different years, eco-sites, varieties, N rates, sowing dates and densities. The plant N uptake index (PNUI) based on NDVI of 807 nm combined with 736 nm was selected as the optimal vegetation index, and a linear model was developed with R2 of 0.878 and RMSE of 1.501 g N m-2 for calibration, and R2 of 0.834, RMSE of 1.316 g N m-2, Slope of 0.934 and Intercept of 0.001 for validation. Then, the effect of the optimal bandwidth of central wavebands on model performance was determined based on the interaction between central wavelength and bandwidth expansion. The results indicated that the optimal bandwidth varies with the central wavelength and with the interaction between the two bands in one vegetation index. These findings are beneficial for prediction and diagnosis of plant N uptake in crop management. Key words: Central Wavelength; Optimal Bandwidth; Plant Nitrogen Uptake; Wheat