Soil Quality Assessment Strategies for Evaluating Soil Degradation in Northern Ethiopia
Table 4
Principal component analysis results using 25 potential soil quality indicators to evaluate eight LUSMS in the Mai-Negus catchment, northern Ethiopia.
Eigenvector
Principal component, PC
Communalities
1
2
3
4
Organic carbon, OC
0.86
0.29
0.12
0.28
0.92
Total nitrogen, TN
0.86
0.21
0.04
0.36
0.92
Earthworm per m2, EW
0.79
0.27
0.28
0.23
0.82
Porosity
0.74
0.38
0.40
0.30
0.94
Zinc, Zn
0.70
0.46
0.31
0.16
0.82
Water-holding capacity, WHC
0.69
0.47
0.47
0.20
0.96
Available phosphorus, Pav
0.69
0.34
0.31
0.11
0.71
A-horizon depth, AHD
0.64
0.37
0.48
0.41
0.94
Soil aggregate stability, SAS
0.60
0.45
0.52
0.33
0.94
Exchangeable potassium, K
0.27
0.83
0.28
0.17
0.86
Cation exchangeable capacity, CEC
0.42
0.76
0.51
0.29
0.95
Exchangeable calcium, Ca
0.41
0.72
0.40
0.28
0.93
Total phosphorous, TP
0.45
0.70
0.38
0.11
0.85
Exchangeable magnesium, Mg
0.53
0.68
0.38
0.24
0.94
Sum base forming cations, SBF
0.45
0.63
0.40
0.26
0.97
Silt
0.19
0.39
0.84
0.04
0.90
Dry bulk density, DBD
−0.40
−0.38
−0.78
−0.30
0.94
pH
0.22
0.26
0.74
0.26
0.82
Sand
−0.34
−0.36
−0.67
−0.30
0.91
EC
0.38
0.44
0.55
−0.03
0.64
Exchangeable sodium, Na
−0.18
−0.18
0.01
−0.57
0.82
Iron, Fe
−0.30
−0.08
−0.13
0.86
0.85
Exchangeable sodium percentage, ESP
−0.17
−0.25
−0.49
−0.59
0.97
Clay
0.51
0.13
0.21
0.63
0.72
Eigenvalue
7.26
5.16
4.79
3.82
—
Variance (%)
30.26
21.51
19.96
15.90
—
Cumulative variance (%)
30.26
51.77
71.73
87.63
—
Boldface eigenvector values correspond to the PCs highly weighted variables examined for the index. Bold-italic factors correspond to the indicators retained in the SQ index. The weight of the variables included in the index was decided using the variance of each factor. PCA-SQI = 0.303OC + 0.0303TN + 0.215CEC + 0.215TP + 0.200silt + 0.200DBD + 0.159Fe. Normalized PCA-SQI = = 0.190OC + 0.190TN + 0.135CEC + 0.135TP + 0.125silt + 0.125DBD + 0.100Fe.
