ESTIMATION OF MINERAL-CONTENT IN NATURAL GRASSLANDS BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY

Near infrared reflectance spectroscopy (NIRS) was tested to predict the nitrogen (N) and mineral concentration [for the elements phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn)] in natural grassland samples. The samples wrere taken from different community types according to the topographic gradient at different maturation stages and during a period of four consecutive years. A subset of 95 samples was selected on the basis of the spectral variation. Chemical values from the calibration sample set were regressed on the corresponding spectral data using a stepwise multiple regression analysis. Another subset of 75 samples was used as the validation set. Standard errors of prediction and correlation coefficients, respectively, were: 0.71 and 0.97 (N), 0.22 and 0.73 (P), 1.83 and 0.84 (K), 0.83 and 0.92 (Ca), 0.15 and 0.92 (Mg), 3.94 and 0.66 (Na), 44 and 0.84 (Mn), 19 and 0.75 (Fe), 1.01 and 0.77 (Co), and 3.9 and 0.79 (Zn).