Soil quality estimation using environmental covariates and predictive models: an example from tropical soils of Nigeria

Ecological Processes

Table 3 Results of the principal component analysis

Indicators	Principal component (PC)				Norm values	Grouping	TDS		MDS
Indicators	PC1	PC2	PC3	PC4	Norm values	Grouping	Com	Weight	Com	Weight
pH	− 0.511	− 0.228	− 0.093	0.215	0.9896	1	0.510	0.058
SOC	0.904	0.125	0.331	− 0.048	1.6260	1	0.826	0.094	0.877	0.279
Ks	0.059	0.608	− 0.189	− 0.263	1.0432	2	0.929	0.105
\(\rho_{b}\)	− 0.709	− 0.014	0.631	− 0.154	1.4333	1	0.4960	.056
Moisture	0.331	− 0.472	0.105	0.366	1.0291	2	0.941	0.107
Porosity	0.534	− 0.031	− 0.796	0.132	1.3035	1	0.498	0.056
MWD	0.242	− 0.247	0.304	0.490	0.8382	4	0.890	0.101	0.447	0.142
SSI	0.502	0.779	0.223	0.142	1.5553	2	0.957	0.108	0.980	0.312
Sand	− 0.315	0.888	− 0.029	0.272	1.5562	2	0.893	0.101	0.835	0.266
Silt	0.370	− 0.684	0.024	− 0.544	1.3899	2	0.503	0.057
Clay	0.024	− 0.628	0.018	0.331	1.0664	2	0.504	0.057
eigenvalue	3.008	2.594	1.294	1.032
Variance (%)	27.32	23.61	11.75	9.10
Cumulative variance (%)	27.32	50.93	62.68	71.78
KMO	0.502
BTS	785.085
df	55
Sig	< 0.01

PC Principal component, Bold PC loadings are considered highly weighted. Bold and underlined factor loadings are selected as minimum data set (MDS); Com Communality, TDS Total data set, MDS Minimum data set. Grouping was based on norm values; Kaiser–Meyer–Olkin Measure of Sampling Adequacy; Bartlett's Test of Sphericity; MC moisture content, df degree of freedom; KMO Kaiser–Meyer–Olkin, BTS Bartlett's test of Sphericity, \(\rho_{b}\) bulk density, MWD mean weight diameter, K_s saturated hydraulic conductivity, SOC soil organic carbon, SSI structural stability index