Abstract:Hyperspectral remote sensing can provide a non-destructive and effective approach for assessing the yield and yield components of oilseed rape timely. A quantitative technique was developed to estimate oilseed rape yield accurately depending on ground-based canopy reflectance spectra. Field experiments were conducted over three growing seasons at different sites (Wuxue and Shayang) in Hubei Province, China. The key parameters, including canopy hyperspectral reflectance during pod-filling period, seed yield and yield components (pod numbers per plant, seed numbers per pod and 1000 seed weight) were monitored. A partial least square (PLS) regression analysis was employed to perform the relationship between raw spectral reflectance (RSR), the first derivative reflectance (FDR) and seed yield and yield components. According to the calibration dataset, the best results were obtained with the FDR-PLS model for the prediction of yield and pod number, which yielded the highest coefficient of determination (R2cal) of 0.96 and 0.98, and the lowest root mean square error (RMSEcal) of 158kg/hm2 and 17 pods/plant, respectively. The tests using the independent validation dataset also showed that the FDR-PLS model could well forecast yield and pod number of winter oilseed rape, with values of R2val of 0.90 and 0.91, RMSEval of 379kg/hm2 and 66 pods/plant, and RPD of 3.11 and 3.12, respectively. The variable importance in projection (VIP) scores resulted from the PLS regression analysis were used to determine the effective wavelengths and reduce the dimensionality of the spectral reflectance data. The newly-developed FDR-PLS model using the effective wavelengths (628nm, 753nm, 882nm, 935nm, 1061nm and 1224nm) performed well in yield prediction with R2val of 0.91, RMSE val of 504kg/hm2 and RPDval of 2.34;Similar results were also obtained for pod number prediction with R2val of 0.87, RMSEval of 82 pods/plant and RPDval of 2.52 using the effective wavelengths (628nm, 758nm, 935nm, 1063nm, 1457nm and 1600nm). Consequently, the yield of winter oilseed rape could be reliably estimated with the in situ developed FDR-PLS method.
