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

Table 4

Optimal selection of the preprocessing technique using the IPLS model.

Parameters	Models	Calibration set (77)			Prediction set (33)
		R^2	RMSEC	Bias	R^2	RMSEP	Bias
N (%)	RAW	0.4576	0.0361	0.0006	0.4894	0.0390	−0.0137
	MSC	0.4710	0.0358	0.0000	0.4891	0.0389	−0.0135
	MC	0.4991	0.0351	0.0006	0.5138	0.0379	−0.0111
	SNV	0.4477	0.0364	0.0000	0.4477	0.0401	−0.0131
	FD	0.4231	0.0368	0.0012	0.4982	0.0383	−0.0119
P (mg·kg^−1)	RAW	0.6194	0.9627	0.0102	0.6445	0.9611	−0.1017
	MSC	0.5739	1.0074	0.0037	0.5636	1.1048	−0.3496
	MC	0.5533	1.0256	0.0322	0.5973	1.0237	−0.2469
	SNV	0.5157	1.0582	0.0073	0.5090	1.0876	−0.2161
	FD	0.6740	0.9087	0.0127	0.7005	0.9029	0.1131
K (cmolc·kg^−1)	RAW	0.6170	0.1586	0.0110	0.6229	0.1802	−0.0364
	MSC	0.7890	0.1253	0.0020	0.7604	0.1700	−0.0864
	MC	0.6977	0.1445	0.0010	0.6746	0.1767	−0.0569
	SNV	0.8104	0.1184	0.0020	0.8268	0.1476	−0.0700
	FD	0.7763	0.1275	0.0030	0.7221	0.1642	−0.0515
Mg^2+ (cmolc·kg^−1)	RAW	0.7702	0.5029	0.0008	0.7764	0.6087	−0.0252
	MSC	0.5490	0.6597	0.0040	0.5817	0.7861	−0.0578
	MC	0.6285	0.6141	0.0040	0.7510	0.6574	0.1355
	SNV	0.5619	0.6557	0.0108	0.5504	0.8051	−0.0274
	FD	0.5103	0.6760	0.0040	0.5544	0.8040	−0.0526
Ca^2+ (cmolc·kg^−1)	RAW	0.6073	3.1258	0.0313	0.5450	3.3710	−0.2670
	MSC	0.7369	2.6520	0.0119	0.7346	2.8916	−0.9689
	MC	0.7773	2.4693	0.0749	0.7868	2.5842	−0.7115
	SNV	0.5755	3.2082	0.0242	0.5809	3.2835	−0.2832
	FD	0.6646	2.9410	0.1847	0.6218	3.2138	−0.1248
pH	RAW	0.3762	0.7206	0.0440	0.3209	0.6363	0.2764
	MSC	0.5937	0.6254	0.0048	0.6042	0.5648	0.0948
	MC	0.5815	0.6316	0.0021	0.4628	0.5458	0.1008
	SNV	0.5624	0.6425	0.0217	0.4477	0.5901	0.0398
	FD	0.6887	0.5648	0.0407	0.5005	0.5301	0.1165