July 18, 2008 Ephemeral gullies are common features on agricultural landscapes. Concentrated water flows can erode cropland soils and carve out these small drainage ditches, which then transport field runoff laden with eroded sediments into nearby streams. In fact, these gullies may lead to soil losses that exceed soil losses from sheet or rill erosion.
Hydraulic engineer Carlos V. Alonso and agricultural engineer Ronald L. Bingner work at the Agricultural Research Service (ARS) National Sedimentation Laboratory in Oxford, Mississippi. They teamed up with University at Buffalo scientists Lee Gordon and Sean Bennett and Natural Resources Conservation Service agricultural engineer Fred Theurer to evaluate the effects of ephemeral gullies on erosion.
Ephemeral gullies are typically filled in throughout the year by agricultural tillage practices. These tillage practices can remove or hide gullies, but the channels often reappear in the same location after subsequent rainstorms. These new channels easily erode the recently tilled fields and start another cycle of gully development and topsoil reduction that can expand across production fields.
The team developed a model to evaluate how tillage practices can affect the formation and evolution of ephemeral gullies and subsequent soil erosion rates. They used historical precipitation data, on-site field observations, and recently developed watershed modeling technology to simulate the effect of tillage practices on long-term ephemeral gully growth and evolution.
During a five-month growing season, tillage activities were simulated using two alternatives: once-a-year conventional tillage and no-till management practice. The collaborators applied the model to replicate a 10-year production span.
Their findings suggest that, on average, tillage in areas prone to ephemeral gully erosion can produce significantly higher soil erosion rates compared to those same regions under no-till management practices. Simulated cumulative ephemeral gully soil erosion rates for the tilled fields were anywhere from 240 percent to 460 percent higher than soil erosion rates from the untilled fields.
The negative effects of tillage simulated in these watershed models reinforce the advantages of using soil conservation technologies such as no-till planting and other reduced tillage management practices.
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