Table 3: Detailed partial least squares regression model results for soil total carbon () prediction from the subsets of mid-infrared diffuse reflectance spectra based on content. The range of values reflects the results of 10 random iterations of the models, and the number in parentheses is the mean. Detailed results are also given for full sample set models with no subsetting for comparison.

Calibration

Validation

RMSE (%)^{c}

RMSE (%)

RPD^{d}

RPIQ^{e}

< 10%

133–147

0.86–0.99

0.21–0.87

56–70

0.71–0.86

0.94–1.26

1.84–2.64

2.24–3.66

(0.94)

(0.58)

(0.82)

(1.10)

(2.34)

(3.05)

> 10%

68–82

0.91–0.99

1.11–4.47

22–36

0.90–0.95

3.48–4.93

3.18–4.29

3.10–8.42

(0.95)

(3.10)

(0.92)

(4.17)

(3.55)

(5.75)

Full sample set

215

0.94–0.99

1.61–3.40

92

0.91–0.96

2.87–4.48

3.33–4.87

2.36–5.69

(0.96)

(2.61)

(0.94)

(3.38)

(4.07)

(3.74)

^{
a}Number of samples. ^{
b}Coefficient of determination. ^{
c}Root mean squared error. ^{
d}Residual prediction deviation. ^{
e}Ratio of performance to interquartile distance.