Comparison of spectral indices to detect nitrogen uptake in winter wheat

Abstract

The present work deals with the use of spectral sensors with spectral indices for the targeted detection of nitrogen uptake in winter wheat (Triticum aestivum). The aim was to quantify and compare the quality and accuracy of known vegetation indices. In addition, for the wavelength range 400 to 900 nm in 2.8 nm steps, all possible two-band indices were calculated and their quality was evaluated as an indicator for the nitrogen supply by means of correlation matrices. The spectral measurements were carried out at defined measurement data for EC 32, EC 39 and EC 65 and then evaluated. In order to assess the quality of the indices, destructive data collections on plant populations in winter wheat were carried out parallel to the spectral measurements. Between the N-record and the indices PLSR, YARA_ALS and REIP_700, coefficients of determination (R²) of up to 0.9 were calculated.

In addition to the R² values, the saturation, i.e. the change in the measured values in comparison to the divergent nitrogen uptake of the plants, was also determined. Particularly high saturating vegetation indices were the NDVI and the SAVI.