The factor-1 loading weights for silt calibration were similar to those for clay content: mostly kaolinite and negative carbonate; however, the factor-2 loading weight had a very high negative contribution from -OH vibrations in organic matter, as indicated by the strong, broad negative band in the 3600-3000 [cm.sup.-1] region.
The first clay loading weight for the <2-mm EP samples (Fig.
The PLSR loading weights (measured as absorbance values, arbitrary units) for factor-1 in the Qld PSD calibration cross-validations (Fig.
A series of strong negative peaks for the Qld clay calibration were observed in the factor-2 loading weights, one near 3520-2450 [cm.sup.-1] due to gibbsite (Nguyen et al.
The loading weights for factor-1 in the NSW clay calibration (Fig.
The EP loading weights for clay, silt and sand were dominated by carbonate, kaolinite and quartz.
Widely different loading weights were required to model the separate Qld and NSW calibrations compared with the calcareous ACU and EP soils, and thus a combined sample set calibration may not succeed.