Die Bodenkultur - Journal for Land Management, Food and Environment

G. Uray, J. Kaufmann and B. Steiner:

Quality assurance of the Near Infrared Reflectance Spectroscopy (NIRS) in fodder analysis: Determination of dry matter, crude protein, crude fibre and crude fat


Analysing dry matter and main nutrient of plant material by near infrared spectroscopy standard quality criteria can be realized with homogenous qualities. In contrast to that practical experience calibrations based on diffuse reflection spectra of heterogenous material of different origin are not yet quite acceptable. In order to establish the quantity of data necessary to obtain satisfactory results when using the calibrations, a comparison of quality parameters of NIR spectroscopy and classical methods has been carried out.

First the variability and the WILCOXON test were used to evaluate pairs of actual and predicted data which had been verified by additional chemical analysis. Looking at 172 samples each with four parameters of WEENDER analysis in four different trials an excellent correspondence between both methods was found.

Additional to the comparison by looking at fundamental mutual amounts according to the WILCOXON test NIR variation coefficients and coefficients of the interlaboratory tests of the ALVA were examined. A further point for good NIRS quality is the share of measured data can be found within these limits.

The results of the validation of the methods show that the requested precision of WEENDER analysis of heterogenous plant material of the same location can be reached by NIRS, if the spectroscopical analysis of one trial is done by daily calibrations.

Key words:  Quality assurance, Comparison of methods, Near Infrared Reflectance Spectroscopy, WEENDER-analysis, Permanent grassland.