We evaluated the effects of a low-phosphorus compost and vegetation (Panicum virgatum) on the ability of three bioretention cells to remove nutrients and total suspended solids (TSS) from storm runoff originating in a dairy farm production area. The three experimental treatments included a bioretention cell without compost or vegetation (C[sbnd]V[sbnd]), a cell with no compost but vegetation (C-V+), and a cell with vegetation and compost (C + V+); the experimental design allowed for isolation of the variables' (i.e., compost and vegetation) effects on pollutant concentration and mass removal. Influent and effluent were monitored for dissolved and total phosphorus (P) and nitrogen (N), and TSS throughout the first growing season post installation. All bioretention cells significantly reduced pollutant concentrations and loads of TSS, total and dissolved P, and NH4 + in the effluent, but significantly exported NOx − to the effluent. All cells reduced total N (TN) concentrations, with significant reduction observed only in the C-V+ cell, which was the only treatment that retained TN load. Compost treatment significantly increased P. virgatum biomass, but not survival during the first year. P. virgatum coverage in compost and no-compost treatments were similar the second year. While low-P compost is still preferable to other composts higher in P content, we cannot conclude that any compost is necessary in the soil media for plant establishment. Due to anticipated nutrients inputs in a setting like this dairy operation site, omitting compost and avoiding nutrient leaching while waiting for plants to grow should be considered for better nutrient removal performance, even if plants may take more time to establish.
Bibliographical noteFunding Information:
The authors acknowledge funding from the University of Vermont College of Agriculture and Life Sciences , and the USDA Hatch Grant ( USDA NIFA Hatch VT-H01916 ) and Northeast Graduate SARE Program ( 032624 – GNE16-124 ). For input on project design and methods development, we thank Josef Gorres, Don Ross, Eric Roy, Joel Tilley, and Dave Whitney. We also thank Rory King, Paige Cascio, and Matt Jackson for assistance with field and laboratory work, Brett Towle for assistance with the drainage map, and Scott Shumway and the staff of the UVM Paul R. Miller Research Complex for assisting with upkeep and maintenance of the research site.
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- Agricultural runoff
- P. virgatum
- Water quality