Quick Determination of Soil Quality Using Portable Spectroscopy and Efficient Multivariate Techniques

Table 3

Optimal selection of the preprocessing technique using the PLS model.

Parameters	Models	Calibration set (77)			Prediction set (33)
		R^2	RMSEC	Bias	R^2	RMSEP	Bias
N (%)	RAW	0.5597	0.0335	0.0038	0.5517	0.0349	0.0061
	MSC	0.4886	0.0353	0.0040	0.7505	0.0276	0.0048
	MC	0.5589	0.0335	0.0038	0.5829	0.0340	0.0059
	SNV	0.4982	0.0350	0.0040	0.7510	0.0276	0.0048
	FD	0.5606	0.0335	0.0038	0.7775	0.0263	0.0046
P (mg·kg^−1)	RAW	0.7533	0.7596	0.0866	0.8121	0.7226	0.1258
	MSC	0.7532	0.8039	0.0916	0.8322	0.6866	0.1195
	MC	0.7818	0.7619	0.0868	0.8380	0.6757	0.1176
	SNV	0.7633	0.7894	0.0900	0.8332	0.6847	0.1192
	FD	0.7899	0.7494	0.0854	0.8384	0.6750	0.1175
K (cmolc·kg^−1)	RAW	0.7894	0.1234	0.0141	0.6616	0.1690	0.0294
	MSC	0.8445	0.1076	0.0123	0.8826	0.1060	0.0184
	MC	0.8566	0.1037	0.0118	0.8701	0.1111	0.0193
	SNV	0.8454	0.1073	0.0122	0.8872	0.1040	0.0181
	FD	0.8781	0.0962	0.0110	0.8789	0.1075	0.0187
Mg^2+ (cmolc·kg^−1)	RAW	0.7437	0.5237	0.0597	0.8014	0.5765	0.1003
	MSC	0.7208	0.5430	0.0619	0.7888	0.5924	0.1031
	MC	0.7385	0.5282	0.0602	0.7946	0.5851	0.1019
	SNV	0.7308	0.5347	0.0609	0.7898	0.5911	0.1029
	FD	0.7119	0.5502	0.0627	0.8078	0.5681	0.0989
Ca^2+ (cmolc·kg^−1)	RAW	0.7629	2.5357	0.2890	0.7982	2.4129	0.4200
	MSC	0.7605	2.5471	0.2903	0.8646	2.0127	0.3504
	MC	0.7629	2.5359	0.2890	0.7973	2.4177	0.4209
	SNV	0.7613	2.5434	0.2899	0.8697	1.9770	0.3442
	FD	0.7830	2.4399	0.2780	0.7871	2.4706	0.4301
pH	RAW	0.8843	0.3624	0.0413	0.5972	0.4738	0.0825
	MSC	0.8912	0.3521	0.0401	0.7667	0.3792	0.0660
	MC	0.8708	0.3817	0.0435	0.5911	0.4765	0.0829
	SNV	0.8914	0.3518	0.0401	0.7855	0.3655	0.0636
	FD	0.8740	0.3773	0.0430	0.5927	0.4758	0.0828