Browsing by Subject "Best Management Practice"

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    Data for: Internal Loading in Stormwater Ponds as a Phosphorus Source to Downstream Waters
    (2019-04-15) Taguchi, Vinicius J; Olsen, Tyler A; Natarajan, Poornima; Janke, Benjamin D; Gulliver, John S; Finlay, Jacques C; Stefan, Heinz G; ; taguc006@umn.edu; Taguchi, Vinicius J; University of Minnesota - St. Anthony Falls Laboratory - Stormwater Research Group
    Stormwater ponds remove phosphorus through sedimentation before releasing captured water downstream. Internal loading can impair net phosphorus removal but is understudied in these highly modified systems. Using a combination of methods, we assessed the prevalence and potential causes of sediment phosphorus release in urban ponds. In a three-year, 98-pond dataset, nearly 40% of ponds had median water column total phosphorus concentrations exceeding the 95% confidence interval for runoff values (0.38 mg/L), suggesting widespread internal loading. In a subsequent intensive monitoring study of four ponds, strong stratification prevented spring and summer diurnal mixing, resulting in persistent hypolimnion anoxia (<1 mg/L dissolved oxygen). Incubated sediment cores from seven ponds demonstrated high anoxic phosphorus release. Sediment analysis revealed high labile organic and redox-sensitive phosphorus fractions with release potential at anoxia onset. Our analyses suggest phosphorus accumulated in stormwater ponds is highly sensitive to internal loading, reducing net removal and contributing to downstream eutrophication.
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    DISSOLVED PHOSPHORUS DYNAMICS AND MANAGEMENT WITHIN THE AGRICULTURAL LANDSCAPE
    (2022-05) Bender, Laura
    Agricultural phosphorus loss was identified as a water quality priority within the Minnesota Nutrient Reduction strategy identifying a 45% yield reduction goal. Implementation plans call for total phosphorus (TP) reduction with traditional management strategies designed for erosion control and particulate nutrient removal, leaving the dissolved, or bioavailable, forms of phosphorus un-accounted for. Substantial yield increases in agricultural tributaries over recent decades highlight the need for dissolved reactive phosphorus (DRP) management, with some sources documenting over 50% DRP contributions to TP loads in Minnesota. DRP, hydrology, management and site-specific factors were investigated at two field research sites in southern Minnesota, with additional data harnessed from the Minnesota Discovery Farms Program. Data was used to assess the impacts of various site and management factors including cover crops, riparian buffers, edge-of-field wetlands, tillage category, fertilizer application and soil properties on phosphorus loads from farm fields and edge-of-field best management practice (BMPs) uptake. Four project objectives were addressed; 1.) to quantify and characterize current and target DRP yields from Southern Minnesota agricultural fields, 2.) to quantify the influence of local field and management conditions on DRP yields, 3.) to assess the effectiveness or inefficacy of common management practices for phosphorus and nitrogen removal, and 4.) to explore novel management strategies for DRP yield reductions including treatment trains, microbial soil amendment and plant harvest. Methodology included hydrologic monitoring, soil assessment, edge of field nutrient concentration analysis and measurement of phosphorus in vegetation to track phosphorus movement through the soil, water and plant components of agroecosystems. Current DRP loss rates from agricultural fields were quantified at 0.49 kg ha-1, with a target DRP yield of 0.27 kg ha-1 to achieve a 45% phosphorus reduction. To meet target yields, project results demonstrated the importance of both surface and subsurface DRP loss pathways, legacy phosphorus monitoring and management and the need for coordinated edge of-field and in-field management strategies. Significant conditions driving drain tile DRP concentrations included manure application rate, number of tillage passes and soil test phosphorus (STP). Significant conditions driving surface DRP concentrations included cumulative manure and fertilizer application rate and STP. STP accumulation was driven most significantly by manure application rate, number of tillage passes, organic matter content, clay content, soil pH and cover crop implementation. Cover crops, which were placed into the context of an agricultural treatment train, were found to reduce subsurface DRP concentrations by 63% and annual yields by .07 kg ha-1 through reduced constituent mobilization at higher flows but also to contribute to increased STP. Crop use efficiency, fertilizer application and soil phosphorus draw down where also associated as part of a mass balance to further correlate management action to DRP yields. Research findings will help to inform agricultural management for DRP removal strategies necessary for setting and meeting realistic nutrient reduction and water quality goals.