CEC, cation exchange capacity; EC, electrical conductivity; SOM, soil organic matter; CI, crusting index; CM, coarse material; HC, hydraulic conductivity; PAWC, plant-available water content; PR, penetration resistance; WY, wheat yield.

**Table 8.** Factor analysis for topsoil in study area.

Factor 5, "soil erosion factor", which includes soil loss and runoff, described 6.46% of the total variation. As expected, there was a positive correlation between soil loss and runoff. Factor analysis was applied to predict erosion in an area intensively cultivated with sugarcane near the city of Piracicaba, São Paulo [53]. The researchers revealed that soil erosion was influenced by slope length and steepness (LS) factor (topographic) more than by the K factor (soil erodibility).

**Variables Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6 Factor 7 Factor 8 Factor 9** Clay, % 0.95 −0.02 0.14 −0.06 −0.02 −0.09 0.10 0.01 −0.01 K Factor, t ha h ha−1 MJ−1 mm−1 −0.88 0.15 0.12 0.00 0.03 −0.15 0.14 −0.15 0.04 Sand, % −0.76 −0.08 −0.35 −0.06 0.08 0.24 −0.33 −0.02 0.03 Silt, % −0.48 0.19 0.40 0.24 −0.11 −0.29 0.44 0.01 −0.04 Fe, mg kg−1 0.11 −0.84 0.10 0.16 −0.15 −0.17 −0.09 −0.11 −0.11 pH −0.06 0.81 0.09 −0.09 0.05 0.13 −0.21 −0.15 −0.08 Cu, mg kg−1 −0.00 −0.59 0.52 −0.06 −0.20 −0.12 −0.25 0.08 −0.13

CEC, cmol kg−1 −0.05 −0.14 0.87 0.00 0.05 0.07 −0.04 −0.03 −0.00

EC, mmhos cm−1 0.40 0.43 0.64 0.23 −0.06 −0.03 −0.08 0.03 0.05

SOM, % 0.13 −0.06 0.10 0.93 −0.03 −0.01 0.13 0.16 0.00

CI, dimensionless −0.19 −0.10 −0.04 0.92 −0.01 0.10 −0.02 0.14 0.01 Soil loss, Mg ha−1 0.01 0.04 −0.05 −0.05 0.88 0.13 0.01 0.12 −0.08 Runoff, dimensionless −0.09 0.18 0.07 0.02 0.78 −0.16 −0.17 −0.19 0.17

HC, cm h−1 0.06 0.21 0.21 −0.04 −0.04 0.71 −0.05 −0.10 0.06

CM, % −0.19 0.14 −0.23 0.09 0.05 0.68 0.00 0.04 −0.13 B, mg kg−1 0.28 −0.15 0.05 0.15 −0.01 0.36 0.13 −0.10 0.31

PAWC, mm 0.19 −0.11 −0.15 0.14 −0.11 0.00 0.77 −0.03 −0.02 Mn, mg kg−1 0.12 −0.03 −0.14 0.24 −0.00 −0.06 −0.39 −0.17 −0.32 P, mg kg−1 0.01 −0.14 0.06 0.14 0.08 0.06 0.02 0.83 −0.02 K, mg kg−1 0.06 0.44 0.08 0.28 −0.17 −0.23 −0.21 0.58 0.07 Zn, mg kg−1 0.25 0.01 −0.11 0.05 −0.08 −0.14 0.14 0.35 −0.10

PR, kPa 0.07 −0.04 −0.13 0.07 −0.01 −0.18 0.09 −0.06 0.74 WY, Mg ha−1 0.18 −0.22 −0.10 0.04 −0.04 −0.23 0.26 0.06 −0.61 Cd, mg kg−1 −0.10 0.03 0.41 −0.21 0.25 0.07 0.26 0.17 0.42 Variance, % 14.57 10.74 9.89 8.37 6.46 6.31 5.73 4.63 4.46 Cumulative variance 14.57 25.31 35.20 43.57 50.03 56.34 62.07 66.70 71.16

CEC, cation exchange capacity; EC, electrical conductivity; SOM, soil organic matter; CI, crusting index; CM, coarse material; HC, hydraulic conductivity; PAWC, plant-available water content; PR, penetration resistance; WY, wheat

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106 Land Degradation and Desertification - a Global Crisis

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yield.

**Table 8.** Factor analysis for topsoil in study area.

Factor 6 was named as "soil conductivity factor", which included the hydraulic conductivity and coarse material content and described 6.31% of the total variation (**Table 8**). We found a strong positive loading for CM (0.68) and HC (0.71). In a study [54], land-use effects on soil compaction considering the saturated hydraulic conductivity (Ks) in a field continuously growing corn and a hayfield both having clay soil in Canada were evaluated. The Ks-values for hayfield-growing soils were approximately 10 or 100 times greater than for the corngrowing soils of which degradation level for upper B horizons had changed from slight to severe. While there was no difference for B horizons in terms of Ks, their results showed that the corn yield was reduced by about 50% due to severe compaction and low Ks. The Ks-values for the 30–50-cm depth can be a reliable indicator for assessing soil structure degradation.

Factor 7, the plant-available water content or "PAWC factor" described 5.7% of the total variation (**Table 8**). The PAWC is considered the most critical indicator for land degradation, especially for dryland farming regions [46]. In dryland regions, spring and summer months are generally dry, and plant water needs are not met due to low and improper distribution of precipitation. The PAWC is a limiting factor for root depth [47–49]. Precipitation water is stored in the soil, depending on soil depth and water-holding capacity. In cases of infiltration rate lower than rainfall intensity, a portion of rainwater may be lost via surface runoff or ponded on the surface. The amount infiltrating into soil may be stored depending on soil depth or lost via deep percolation or underground lateral flow in sloping layered soils. As a result, the amount of water stored in the soil may be critical in areas where water is the principal growthlimiting factor [47, 48]. Spatial variability of topsoil (0–30 cm) and subsoil (30–60 cm) in the Kazova Plain was investigated by factor analysis [55]. Six of 10 variables for both top and subsoils were loaded in four factors accounting for 94.80 and 92.80% of total variance, respectively. The results showed that the plant-available water content and available phosphorus content (P) were the most important soil properties for soil management and soil fertility studies in the study area.

Macroelements K and P were loaded in Factor 8. Factor 8 was named as "macroelement factor". The loadings showed a high correlation between these two variables. The imbalance of macronutrients (e.g., N, P, K, Ca, Mg, and S) and microelements (e.g., Zn, Cu, Mo, B, and Se) may cause a yield decline in degraded soils. Factor analysis has been used to identify the most sensitive indicators of some soil characteristics for evaluating soil tillage in Vertisol and Entisols in the Bafra province of Turkey [56]. The soil physicochemical properties of Vertisols were grouped in three groups and of Entisols were grouped in two groups. Available water content, field capacity, soil organic matter, wilting point, and CaCO3 were in the first group; bulk density, sand, and carbon were in the second group; and penetration resistance was in the third group for Vertisols. Soil organic matter, available water content, wilting point, field capacity,

soil organic matter, sand, and bulk density were in the first group and CaCO3, silt, and penetration resistance were in the second group for Entisols.

