Subsurface tile-drainage is widely used to increase crop yields in poorly drained, agricultural landscapes across the nation. Sediment-bound phosphorus (P) loadings from tile-drainage are contributing to the excessive richness of nutrients in a body of water, through water run-off, and increasing the prominence of harmful algae in downstream waterbodies. There are major gaps in understanding of sediment erosion and transport dynamics through tile-drains, which has limited our ability to manage these contaminants from agricultural fields. This research will provide funding for a tenure-track Assistant Professor, and a graduate research assistant from the University of Kentucky to conduct extended site visits at the National Soil Erosion Research Laboratory (NSERL) in West Lafayette, Indiana. The PI and his student will collaborate with researchers at NSERL to perform laboratory rainfall simulations to study mechanisms of sediment erosion and transport through subsurface soils. The research team will also enhance computer simulation tools that can capture tile sediment P loadings from fields in order to improve management strategies. Tile-drainage is increasingly implemented in the PI’s state of Kentucky, as well as food-production systems across the country. This research will improve infrastructure for researching and managing tile-drainage water quality, advance graduate curricula at the PI’s home institution, and provide training for an underrepresented student in STEM.
Recent studies have highlighted the importance of dissolved reactive phosphorus (DRP) that is regenerated from streambed sediments as a major source of watershed-scale DRP loading. There is now renewed interest in quantifying and managing sediment-bound particulate P (PP) delivered through tile-drains. Mechanisms controlling sediment erosion and transport dynamics in macropores are not well understood, particularly the impact of biological crust development on macropore walls and how it influences flow pathway dynamics and sediment erodibility. Further, field-scale controls on PP delivery to tile drains have been hypothesized, but not quantified, which stems from a lack of field datasets and limited representation of subsurface PP delivery through tile drains in agricultural water management models. The research team will collaborate with the National Soil Erosion Research Laboratory (NSERL) to study the impact of macropore biological crust development on sediment erosion and flow pathway dynamics. Fellowship activities include the use of rainfall experiments on undisturbed soil lysimeters with a growth and control condition. The team will also modify the Water Erosion Prediction Project (WEPP) model to include subsurface flow pathways and sediment P erosion and transport routines for tile drainage, which will be evaluated at both field and watershed scales using long-term datasets managed by NSERL. The infrastructure developed in this proposal may be used to inform weighting factors and model structure for empirically-based tools used by practitioners, such as P-indices. The proposed research activities will improve mechanistic understanding of subsurface erosion processes, advance numerical modeling infrastructure at field-watershed scales for subsurface drained agroecosystems, and will quantify the prominent mechanisms causing PP transport to tile drains.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
