Patrick Drohan, Ecosystem Service and Management, Penn State University
2021 NCSS National Conference
Advising farm operators how to reduce phosphorus (P) runoff from non-point source agricultural fields is typically done in the central Appalachians USA using a combination of farm visits, conservation plan development and P-Index application. However, recent research in Europe has shown that the identification of areas of high runoff mobilization potential (hydrologically sensitive areas (HSA)) that coincide with a P sources (a critical source areas (CSA)) can better identify site-specific areas of risk of P transfer to surface waters. We developed a CSA Index model for four case study sub-watersheds within the Mahantango watershed using: LiDAR to model sub-field topography; SSURGO data; agronomic based soil test P levels; and field geophysics to identify restrictive layers. The CSA index was developed using agronomic (within field boundary) Mehlich-3 soil test P analysis at 5 and 15 cm and evaluated using high-resolution within field environmental testing (within CSA). Results suggest that both approaches to CSA Index development produce similar site-specific field data. Environmental testing more specifically identifies areas to target for management and can give farmers site-specific information on how their behavior change can improve water quality. Most importantly, the application of a CSA index shows that traditional riparian buffer designs being used may in some cases be inadequate to capture current runoff and in many other cases over-designed.
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