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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #383893
Research Project: Sustaining Agroecosystems and Water Resources in the Northeastern U.S.

Location: Pasture Systems & Watershed Management Research

Title: Estimating dissolved phosphorus losses from legacy sources in pastures: The limits of soil tests and small-scale rainfall simulators

Author
item NASH, DAVID - University Of Melbourne
item WEATHERLEY, ANTHONY - Consultant
item Kleinman, Peter
item SHARPLEY, ANDREW - University Of Arkansas

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2021
Publication Date: 7/10/2021
Citation: Nash, D.M., Weatherley, A.J., Kleinman, P.J., Sharpley, A.N. 2021. Estimating dissolved phosphorus losses from legacy sources in pastures: The limits of soil tests and small-scale rainfall simulators. Journal of Environmental Quality. 1-21. https://doi.org/10.1002/jeq2.20265.
DOI: https://doi.org/10.1002/jeq2.20265

Interpretive Summary: Legacy phosphorus represents one of the most difficult sources of phosphorus to runoff to prevent. Scientists from the United States and Australia developed a comprehensive model to understand the contributions of legacy phosphorus to runoff waters. Their findings have relevance to the management and science of non-point source phosphorus pollution.

Technical Abstract: A legacy of using P fertilizers on grazed pastures has been enhanced soil fertility and an associated, increased risk of P exports. Rainfall simulation has been extensively used to develop relationships between soil test P (STP) and dissolved P (DP) as part of modelling efforts scrutinizing the impact of legacy P. This review examines the applicability of that approach. Initially we examine a mixing layer model with chemical transfer to describe DP mobilization. In that model, readily available P in the mixing layer is rapidly exhausted with a second, rate limited process, where DP concentrations depend on contact time, being primarily responsible for subsequent P mobilization. In that instance DP concentrations should reflect soil/water contact. The model is shown to be consistent with field data and possible sources of P are presented. Experimental protocols used for rainfall simulation studies are then examined including soil preparation, scale and measurement duration, and hydrology. Based on that analysis and the model of P mobilization, it is suggested rainfall simulation experiments have significant limitations for developing relationships based on STP that purport to predict the risk legacy P poses for downstream water resources.