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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #329075

Title: Increased soluble phosphorus loads to Lake Erie: Unintended consequences of conservation practices?

Author
item JARVIE, HELEN - Centre For Ecology & Hydrology
item JOHNSON, LAURA - Heidelberg University, Ohio
item SHARPLEY, ANDREW - University Of Arkansas
item Smith, Douglas
item BAKER, DAVID - Heidelberg University, Ohio
item BRUUSELMA, TOM - International Plant Nutrition Institute (IPNI)
item CONFESSOR, REM - Heidelberg University, Ohio

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2016
Publication Date: 1/12/2017
Publication URL: https://handle.nal.usda.gov/10113/5852146
Citation: Jarvie, H.P., Johnson, L.T., Sharpley, A.N., Smith, D.R., Baker, D.B., Bruuselma, T., Confessor, R. 2017. Increased soluble phosphorus loads to Lake Erie: Unintended consequences of conservation practices? Journal of Environmental Quality. 46:123-132. https://doi.org/10.2134/jeq2016.07.0248.
DOI: https://doi.org/10.2134/jeq2016.07.0248

Interpretive Summary: Cumulative daily phosphorus data over the last 35 years show that the early 2000s marked the start of large-scale and widespread increases in soluble phosphorus entering western Lake Erie basin, from three major tributaries: the Maumee, Sandusky and Raisin Rivers. These elevated soluble phosphorus loads have been sustained over the last 12 years, with soluble phosphorus load increases exceeding the corresponding increases in river flow, indicating that additional phosphorus sources have contributed to the increased soluble phosphorus. We estimated the contributions from (a) increased runoff from changing weather and precipitation patterns and (b) increased in soluble phosphorus delivery (the combined effects of increased source availability and transport efficiency) increased soluble phosphorus after 2002. Approximately 70% of the post-2002 soluble phosphorus load increase was attributable to enhanced delivery, with higher runoff volumes accounting for the remaining 30%. Increased soluble phosphorus delivery occurred concomitantly with declining watershed phosphorus budgets, so the phosphorus was not coming from additional P inputs into these watersheds. Long-term, large-scale changes in land management designed to reduce soil erosion and particulate phosphorus losses from surface runoff, through reduced tillage and tile drainage, also occurred within these watersheds. However, these practices can inadvertently result in a build-up of phosphorus at the soil surface and increased transmission of soluble phosphorus via sub-surface drainage. Our findings point to an “inconvenient truth” that conservation practices designed to reduce soil erosion and particulate phosphorus transport, may have had unintended, cumulative and converging impacts, contributing to the increased western Lake Erie basin soluble phosphorus fluxes, reaching a critical threshold around 2002.

Technical Abstract: Cumulative daily flux timeseries show that the early 2000s marked the start of large-scale and widespread increases in riverine soluble reactive phosphorus fluxes entering western Lake Erie basin, from three major tributaries: the Maumee, Sandusky and Raisin Rivers. These elevated soluble reactive phosphorus fluxes have been sustained over the last 12 years, with soluble reactive phosphorus load increases exceeding the corresponding increases in runoff, indicating that additional labile phosphorus sources have contributed to the increased soluble reactive phosphorus fluxes. Empirical regression models estimated the contributions from (a) increased runoff from changing weather and precipitation patterns and (b) increased in soluble reactive phosphorus delivery (the combined effects of increased source availability and transport efficiency), to the increased soluble reactive phosphorus fluxes after 2002. Approximately 70% of the post-2002 soluble reactive phosphorus load increase was attributable to enhanced soluble reactive phosphorus delivery, with higher runoff volumes accounting for the remaining 30%. Increased soluble reactive phosphorus delivery occurred concomitantly with declining watershed phosphorus budgets, indicating changes in wider watershed functioning. Long-term, large-scale changes in land management designed to reduce soil erosion and particulate phosphorus losses from surface runoff, through reduced tillage and tile drainage, also occurred within these watersheds. However, these practices can inadvertently result in a build-up of labile phosphorus fractions at the soil surface, and increased transmission of soluble phosphorus via sub-surface drainage. Our findings point to an “inconvenient truth” that conservation practices designed to reduce soil erosion and particulate phosphorus transport, may have had unintended, cumulative and converging impacts, contributing to the increased western Lake Erie basin soluble reactive phosphorus fluxes, reaching a critical threshold around 2002.