Long term conservation practice effects on agricultural soil loss from concentrated and distributed sources

Area of Science:

• Agricultural Science
• Environmental Science
• Hydrology

Background:

• Soil erosion and sediment transport from agricultural fields pose significant environmental challenges.
• Conservation practices are crucial for mitigating soil loss, yet their watershed-scale effectiveness is complex to quantify.
• Understanding the impact of integrated, spatiotemporal conservation strategies on diverse erosion sources is essential.

Purpose of the Study:

• To investigate the impact of conservation practices on sheet/rill and ephemeral gully erosion at field and watershed scales.
• To quantify sediment load reductions using the AnnAGNPS model before and after conservation implementation.
• To evaluate the effectiveness of conservation practices against different erosion sources and extreme weather events.

Main Methods:

• Utilized data from a USDA Conservation Effects Assessment Project (CEAP) watershed draining into the Chesapeake Bay.
• Characterized ephemeral gullies and conservation practices at a raster grid scale for field and watershed evaluations.
• Employed the AnnAGNPS watershed pollution model to simulate sediment loads across three distinct time periods (1990-2000, 2000-2010, 2010-2020).

Main Results:

• Implemented conservation practices showed a potential reduction of approximately 10% from ephemeral gully sources and 30% from sheet/rill sources.
• Overall annual average sediment concentration decreased by 60% after conservation practices were implemented.
• Conservation practices were less effective in mitigating sediment from ephemeral gully sources compared to sheet/rill erosion.

Conclusions:

• Conservation practices offer significant reductions in agricultural sediment loads, particularly from sheet/rill erosion.
• Ephemeral gully erosion remains a challenge, requiring targeted mitigation strategies.
• Extreme precipitation events (recurrence interval > 250 years) can contribute substantially to annual sediment loads, necessitating research into their impact and management.