Winter wheat (
Triticum aestivum L.) is an important rotation crop in southern Gifu prefecture, but rotational use of dried paddy fields often reduces grain quality. Consequently, grain quality varies greatly throughout a single area. This study is intended to evaluate
in situ canopy reflectance to predict the total dry matter (DM), leaf area index (LAI), and leaf nitrogen concentration (N
conc). In a field experiment including four levels of N application, hyperspectral reflectance data (400–950 nm) were obtained for winter wheat during five growth stages. Band selection applied using a normalized difference vegetation index (NDVI) formula yielded the best-fitted two-pair waveband. Several paired bands were also indicated, which had higher
R2 values of DM (
R2 > 0.8), LAI (
R2 > 0.4), and N
conc (
R2 > 0.5) than those in typical red and near-infrared (NIR) based NDVI(
R2 = 0.39, 0.27, and 0.01 respectively in DM, LAI, and N
conc). Partial least squares (PLS) regression analyses using the best two-pair NDVI predictions improved the predictive accuracy for DM (
R2 = 0.93), LAI (
R2 = 0.80), and N
conc (
R2 = 0.83). Furthermore, the model using first derivative reflectance (FDR) more precisely predicted DM (
R2 = 0.95) and N
conc (
R2 = 0.88) than that using reflectance spectra. These findings suggest that PLS can provide better prediction than conventional methods using a single waveband or band combination. Strong correlations were found in regions with shorter wavelengths: green(525–570 nm), red edge (720–780 nm), and NIR (930–950 nm) regions to DM and LAI; and blue (425–490 nm) and red regions (645–685 nm) to N
conc. These results suggest that important wavelength regions are green, red edge, and NIR regions for DM and LAI, and blue and red regions for N
conc.
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