Iron Oxides Erodibility Interactions for Soils of the Memphis Catena
1998
Rhoton, F. E. | Römkens, M. J. M. | Lindbo, D. L.
In the Memphis catena, the well-drained Memphis (fine silty, mixed, active, thermic Typic Hapludalfs) is more erodible than the moderately well-drained Loring (fine silty, mixed, active, thermic Oxyaquic Fragiudalfs) and Grenada (fine silty, mixed, active, thermic Glossic Fragiudalfs). We hypothesized that soil wetness and Fe oxide status affects the erodibility of these soils. Samples (<2 mm) of A- and B-horizons, collected from representative pedons at five locations, were characterized for standard physical and chemical properties. Simulated rainfall was applied (64 mm h⁻¹) to additional samples (<8 mm) in a rainfall simulator pan that had a 0.6 m × 0.6 m test area. Water dispersible clay (WDC) and soil loss averaged 7.2% and 9.21 Mg ha⁻¹ for Memphis, 6.8% and 8.85 Mg ha⁻¹ for Loring, and 6.1% and 8.71 Mg ha⁻¹ for Grenada. Sediment Feₒ, Fed, and Feₒ/Fed ratios were about 0.80, 1.5, and 0.50 times that of the soil, respectively. Correlation coefficients (r) for WDC and soil loss vs. Fe oxide variables exceeded 0.90 in some horizons, whereas, organic C (OC) and % clay were generally <0.60. However, OC vs. % sediment <53 µm had r values of 0.87 compared to 0.59 for some Fe oxide variables. Regression models derived for WDC and soil loss had Fe oxide parameters as principal variables in the best fit models and coefficients of determination that ranged from 0.208 to 0.922 (significant at P ≤ 0.01). Results suggest that Fe oxides are more important than OC and clay content for determining the erodibility of these soils, particularly Feₒ/Fed ratios which are negatively correlated with WDC and soil loss.
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