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ARS Home » Southeast Area » Stoneville, Mississippi » Sustainable Water Management Research » Research » Publications at this Location » Publication #416264
Research Project: Development of Best Management Practices, Tools, and Technologies to Optimize Water Use Efficiency and Improve Water Distribution in the Lower Mississippi River Basin

Location: Sustainable Water Management Research

Title: Phosphorus lability across diverse agricultural contexts with legacy sources

Author
item Simpson, Zachary
item Mott, Joshua
item Elkin, Kyle
item Buda, Anthony
item FAULKNER, JOSHUA - University Of Vermont
item Hapeman, Cathleen
item McCarty, Gregory
item FOROUGHI, MARYAM - University Of Maryland
item HIVELY, W. DEAN - Us Geological Survey (USGS)
item King, Kevin
item Osterholz, William
item Penn, Chad
item Williams, Mark
item Witthaus, Lindsey
item Locke, Martin
item PAWLOWSKI, ETHAN - Oak Ridge Institute For Science And Education (ORISE)
item Dalzell, Brent
item Feyereisen, Gary
item DOLPH, CHRISTINE - University Of Minnesota
item Bjorneberg, David
item Nouwakpo, Sayjro
item Rogers, Christopher
item SCOTT, ISIS - Kansas State University
item Bolster, Carl
item DURIANCIK, LISA - Natural Resources Conservation Service (NRCS, USDA)
item Kleinman, Peter

Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Phosphorus (P) from past nutrient management can contribute to water quality concerns decades after it was applied as fertilizer or manure: a dynamic known as ‘legacy P’. Legacy P presents a long-lasting obstacle for P management. The USDA Legacy P project was created to provide critical research on legacy P dynamics across a variety of agricultural settings and scales. Here, we analyzed more than 600 soils and sediments from seven sites where legacy P is a concern. Across all sites, potentially mobile P stores could supply significant dissolved P losses for decades. We built a model to predict the potential of soil or sediment P to release to water; this model, based on fundamental P sorption chemistry, proved highly predictive across the diversity of physical and chemical characteristics studied. These findings can guide the future generation of P transport models, meaning that we can better predict the impacts of legacy P on water quality such as harmful algal blooms.

Technical Abstract: The buffering of phosphorus (P) in the landscape delays management outcomes for water quality. If stored in labile form, P may readily pollute waters. Herein, we studied P lability for more than 600 soils and sediments across seven study locations in the USA. Labile P stocks were large enough to sustain high P losses for decades, indicating the transport-limited regime typical of legacy P. Sediments were often more sorptive for P than nearby soils. Soils in the top 5 cm had 1.3 to 3.0 times more labile P than soils at 5–15 cm. Stratification in soil test P and total P was, however, less consistent. As environmental P exchange via sorption follows the difference in intensity between solution and the surface of soil or sediment, we built a model for the equilibrium phosphate concentration at net zero sorption (EPC0) as a function of labile P quantity and buffer capacity. Despite widely varying properties across sites, the model generalized well for all soils and sediments: EPC0 increased sharply with more labile P and to greater degree when buffer capacity was low or sorption sites were likely more saturated. This quantity-intensity-buffer relationship is central to the P transport models we rely on today. Our data inform the improvement of such P models, which will be necessary to predict the impacts of legacy P. Further, this work reaffirms the position of labile P as a key focus for environmental P management.