Effects of consolidation on soil erosion properties and their relation to soil physical quality indicators

Authors: Wilson, Glenn; ZHANG, TANYU - Northeast Normal University; Wells, Robert - Rob; LIU, BAOYUAN - Northwest A&f University

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2019
Publication Date: 1/13/2020
Citation: Wilson, G.V., Zhang, T., Wells, R.R., Liu, B. 2020. Effects of consolidation on soil erosion properties and their relation to soil physical quality indicators. Soil & Tillage Research. 198: 1-12. https://doi.org/10.1016/j.still.2019.104550.
DOI: https://doi.org/10.1016/j.still.2019.104550

Interpretive Summary: Consolidation of soil by alternating cycles of wetting then drying following tillage rapidly changes the soil physical properties but little is known about how these changes impact the soil erosion properties. The objectives of this study were to develop relationships between erosion properties and rainfall as well as other soil physical properties in order to predict soil erodibility and critical shear stress changes due to consolidation following a series of wetting and drying cycles. Air-dried soil for four contrasting soil series was loosely filled into soil cylinders to simulate freshly tilled conditions. Soil physical properties and erosion properties were determined at six time periods (0, 1, 3, 5, 7, 10 days) following daily rainfalls of 33 mm/h for 1 hour and 24 hours of drainage and drying. The Jet Test device was used to determine erodibility and critical shear stress. The bulk density increased with time due to consolidation in response to rainfall with the largest increase (50-100% of the total) occurring after the first wetting/drying cycle. The Onstad consolidation model tended to over-predict this initial surface bulk density increase, whereas, an exponential model better represented the surface and depth-averaged bulk density changes for the four soils tested. The shear strength and soil penetration resistance increased dramatically after the first wetting/drying cycle then decreased to a fairly stable value in response to additional wetting/drying cycles. The saturated hydraulic conductivity decreased so rapidly with accumulated rainfall that the standard decay model could not match the decrease in hydraulic conductivity as the soil consolidated. The best indicators of erodibility changes due to consolidation by wetting/drying cycles were accumulated rain, surface bulk density, , saturated hydraulic conductivity, and soil penetration resistance at the 1.3 cm depth. The best indicators of critical shear stress changes due to consolidation were accumulated rainfall, soil penetration resistance at 1.3 cm and saturated hydraulic conductivity. Because these erosion parameters had intercepts that were dependent upon the soil series, prediction of changes in soil erosion with time following tillage will be soil-specific.

Technical Abstract: Consolidation of soil by wetting and drying cycles following tillage rapidly changes the soil physical properties but little is known about how these changes impacts the soil erosion properties. The objectives of this study were to develop regression equations to predict soil erodibility (Kd) and critical shear stress (tc) changes due to consolidation based upon changes in soil bulk density, saturated hydraulic conductivity, water content, soil penetration strength and surface shear strength following a series of wetting and drying cycles. Air-dried soil for four contrasting soil series was loosely filled into 20 soil cylinders each (80 total) to simulate freshly tilled conditions. Soil physical and erosion properties were determined at six time periods (0, 1, 3, 5, 7, 10 days) following daily simulated rainfall of 33 mm/h for 1 hour and 24 hours of drainage/drying. The Jet Test device was used to determine Kd, and tc. The bulk density increased with time due to consolidation following the simulated precipitation events with the largest increase (50-100% of the total) occurring after the first wetting/drying cycle. The Onstad consolidation model tended to over-predict this initial surface bulk density increase, whereas, an exponential model better represented the surface and depth-averaged bulk density changes for the four soils tested. The shear strength and soil penetration resistance increased dramatically after the first wetting/drying cycle then decreased to a fairly stable value in response to subsequent wetting/drying cycles. The saturated hydraulic conductivity, Ks, decreased so rapidly with accumulated rainfall that an exponential decay model could not match the decrease in Ks as the soil consolidated. The best indicators of erodibility changes due to consolidation by with wetting/drying cycles were accumulated rain, surface bulk density, saturated hydraulic conductivity, and soil penetration resistance at the 1.3 cm depth. The best indicators of critical shear stress changes due to consolidation were accumulated rainfall, soil penetration resistance at 1.3 cm and saturated hydraulic conductivity. Because these erosion parameters had intercepts that were dependent upon the soil series, prediction of changes in soil erosion with time following tillage will be soil-specific.