Erodibility of claypan soils: Identifying erosion mechanisms for sustainable reduction of sediment loss

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1705823 (Sassenrath). Claypan soils cover approximately 4 million hectares in the US and are characterized by a highly impermeable layer below the topsoil. This impermeable layer may create lateral flow within the soil matrix that increases the rate of erosion of the topsoil. Surface vegetation increases the erosion resistance at the surface of claypan soils; however, the limited topsoil continues to diminish annually. This research addresses the need to identify the mechanisms that are causing this sediment loss and restore the ecological function of soil and water ecosystems before the topsoil is irretrievably lost.The objective is to test the hypothesis that the impermeable claypan layer is increasing soil erosion by undermining topsoil. This will be achieved by measuring the erodibility and strength of soil samples from areas where soil management practices are identical yet soil loss is variable. The variability has been identified by aerial imagery, terrain analysis, yield maps and surface conductivity measurements. Geotechnical delineation of erodibility will be measured using a variety of geotechnical methodologies, including an Erosion Function Apparatus in the laboratory and a Jet Erosion Test in the field. The primary hypothesis of this research is that topsoil is undergoing undermining erosion within the soil core which is further reducing its shear strength and thus increasing the erodibility. Measured strength and erosion parameters will be used to better predict sediment loss. The research plan has been developed in close collaboration with local landowners. The understanding of the fundamental mechanisms that are resulting in the claypan erodibility phenomena will be shared with landowners so appropriate land use management practices can be developed and implemented. The multidisciplinary leadership team of an agronomist, a geotechnical engineer, and a mass communications specialist will work closely with Extension personnel, conservationists and landowners to address this multifaceted problem and implement change.