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Research Project: Technologies for Managing Water and Sediment Movement in Agricultural Watersheds

Location: Watershed Physical Processes Research

Title: Effect of water potential and void ratio on erodibility for agricultural soils

Author
item LIU, QIANJIN - Linyi University
item Wells, Robert - Rob
item Vacant,
item HE, J - Capital Normal University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2017
Publication Date: 6/30/2017
Publication URL: http://handle.nal.usda.gov/10113/5934972
Citation: Liu, Q.J., Wells, R.R., Dabney, S.M., He, J.J. 2017. Effect of water potential and void ratio on erodibility for agricultural soils. Soil Science Society of America Journal. 81:622-632. doi:10.2136/sssaj2016.11.0369.

Interpretive Summary: The initiation and susceptibility of soil to erosion has been documented for decades. A common thread within this research has been our inability to determine how two, seemingly similar, samples yield different values. Scientists have developed new tests and solution methods to glean insight into the causes for discrepancy. A set of submerged scour hole erosion tests (JET; Jet Erosion Test) were designed to measure the impact of initial soil water, bulk density and potential (either negative like suction or positive like seepage) on soil erosion parameters; soil erodibility and critical shear stress. We found that there was weakening and higher likelihood of erosion in positive potential conditions (seepage) and strengthening and lower likelihood of erosion in negative potential conditions (suction). The initial packing was the major contributor to erosion parameter estimates. Using statistical modeling, we determined that silt content, bulk density and water potential were very important contributors to critical shear stress (initiation of motion parameter), and clay content, bulk density, and critical shear stress were very important contributors to soil erodibility (rate of soil erosion).

Technical Abstract: Soil erodibility has confounded researchers for decades. Difficulties arise with initiation of motion, pore-water status, physical, and perhaps biological, material properties and type of applied energy (i.e. rainfall, runoff, freeze/thaw, wind). Though specific tests have been developed to determine critical shear stress and soil erodibility, solutions do not seem to conform to theory. We have linear and non-linear models for erosion assessment and, although each provides practical information for planning and management, all share a need to improve predictions for soil detachment. Here, a series of submerged jet tests (JET) are performed on samples prepared to represent agricultural conditions (i.e. reduced bulk density), five initial soil moistures, and four imposed water potentials. Results, for both coarse- and fine-grained soils, indicate that critical shear stress for can be predicted with knowledge of the silt content, void ratio and water potential; and soil erodibility can be predicted with knowledge of critical shear stress, clay content and void ratio. This study was limited by the number of soils examined; however, the results are thought provoking.