Table 3.

The modeling results of different soil types and temperatures by partial least squares (PLS).

Group	Soil Type		Calibration Set			Prediction Set
		N1	Rc	RMSEC (g/kg)	N2	Rp	RMSEP (g/kg)	RPD
1 (50 °C)	Black soil	118	0.9525	0.198	58	0.9216	0.228	2.72
	Loess	118	0.9609	0.077	58	0.9466	0.112	2.71
	Calcium soil	118	0.9881	0.057	58	0.9258	0.128	2.69
2 (80 °C)	Black soil	118	0.9417	0.216	58	0.9368	0.217	2.82
	Loess	118	0.9935	0.033	58	0.9568	0.090	3.31
	Calcium soil	118	0.9173	0.132	58	0.9316	0.119	2.75
3 (95 °C)	Black soil	118	0.9906	0.086	58	0.9065	0.273	2.22
	Loess	118	0.9739	0.066	58	0.9721	0.067	4.34
	Calcium soil	118	0.9269	0.129	58	0.9588	0.094	3.89
4 (25 °C)	Black soil	118	0.7773	0.391	58	0.6849	0.480	1.26
	Loess	118	0.3507	0.267	58	0.4529	0.287	1.09
	Calcium soil	118	0.5332	0.286	58	0.5568	0.258	1.34