Table 5: Calibration and validation performance statistics of laboratory spectra.

Parameter Clay Model name Number of samples (cal/val) Preprocessing Number of LV SDcal† SDval† SEC SD/SEC SEP RPD Lab_2004_Clay 20/115 Absorption 6 48.21 75.21 0.76 29.30 1.65 26.59 2.54 Lab_2005_Clay 38/97 First derivative of absorption 5 49.32 70.06 0.90 17.42 2.87 20.77 3.25 Lab_2005_Clay 38/29 First derivative of absorption 5 49.32 48.08 0.90 17.42 2.87 19.48 2.69 Lab_2008_Clay 11/124 Absorption 5 39.92 69.18 0.70 35.68 1.28 35.55 1.86 Parameter Organic carbon Model name Number of samples (cal/val) Preprocessing Number of LV SDcal† SDval† SEC SD/SEC SEP RPD Lab_2004_OC 20/115 Absorption 2 2.53 3.77 0.51 2.36 1.34 2.36 1.71 Lab_2005_OC 38/97 Absorption 6 2.87 3.90 0.88 1.11 2.67 1.92 2.16 Lab_2005_OC 38/29 Absorption 6 2.87 2.63 0.88 1.11 2.67 1.94 1.93 Lab_2008_OC 11/124 First derivative of absorption 4 1.49 4.12 0.78 0.97 1.52 2.46 1.58

†SD: standard deviation of estimated parameter values in (g kg−1), : coefficient of determination, SEC: standard error of calibration in (g kg−1), SEP: standard error of validation in (g kg−1), RPD: ratio of performance to deviation.