Table 2.

Comparison of three mathematical modeling methods.

Group	Model Method	R1 of the Correction Set	R2 of the Prediction Set	Calibration Set RMSEC	Prediction Set RMSEP
Strict pretreatment soil samples	PLS	0.9901	0.9865	0.00292	0.00330
	UVE	0.9937	0.9900	0.00233	0.02860
	CARS	0.9949	0.9900	0.00210	0.00275
grinding and drying soil samples	PLS	0.8548	0.9759	0.01071	0.00633
	UVE	0.9176	0.9512	0.00821	0.00695
	CARS	0.9202	0.9732	0.00808	0.00540
drying soil samples	PLS	0.7872	0.7988	0.01216	0.01330
	UVE	0.7860	0.8006	0.01219	0.01340
	CARS	0.8169	0.7950	0.01137	0.01320