Rapid estimation of leaf nitrogen content in apple-trees based on canopy hyperspectral reflectance using multivariate methods

•Hyperspectral reflectance at canopy-scale of apple-trees was measured using the portable spectroradiometer.•The spectra of apple tree canopy affected by floating dust particles were well preprocessed by SNV-FD.•Random frog (Rfrog) was used to extract feature bands for estimating leaf N content in apple-trees.•The combination of SNV-FD, Rfrog and ELM was feasible and reliable for estimating the leaf N content in apple-trees.