Application of near‐infrared reflectance spectroscopy to chemical analysis of heterogeneous and botanically complex grassland samples

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Abstract
The potential of near‐infrared reflectance spectroscopy (NIRS) for determining the chemical composition of heterogeneous, botanically complex semi‐natural grassland herbage was assessed. Samples were collected over four consecutive years at different maturation stages and were analysed by chemical and NIRS procedures for crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin and cellulose. A subset of samples was selected on the basis of spectral features in order to establish calibration equations, while the other samples were used for validation. The wavelengths selected by using multiple regression were similar to others previously reported. The ranges of correlation coefficients and standard errors of prediction, respectively, for the various components when NIRS and chemical procedures were compared were as follows: protein, 0·93‐0·95 and 0·57‐0·70; NDF, 0·92‐0·93 and 2·06‐2·37; ADF, 0·85‐0·87 and 1·42‐1·56; lignin, 0·90‐0·94 and 0·45‐0·59; cellulose, 0·82‐0·86 and 1·27‐1·45. The accuracy of predictions for these chemical components was similar to previously reported values.