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Crow_Thesis_20220422.pdf (3.05 MB)

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Evaluating the Impacts of Climate and Stacked Conservation Practices on Nutrient Loss from Legacy Phosphorus Agricultural Fields

Crow, Rachelle Leah
http://rave.ohiolink.edu/etdc/view?acc_num=osu1650471341835724

Abstract Details

2022, Master of Science, Ohio State University, Food, Agricultural and Biological Engineering.
Agricultural nutrient loss in the Western Lake Erie Basin (WLEB) leads to elevated nutrient levels in Lake Erie, resulting in harmful algal blooms and anoxic conditions, decreased fish populations, and reduced recreation and tourism revenues. To combat this issue, the Ohio Phosphorus Task Force set a goal to decrease the phosphorus (P) load to the WLEB by 40% from 2008 spring loads. To meet this goal, efforts are underway to minimize the amount of P transported from agricultural fields to surface water using best management practices (BMPs). While many BMPs aim to decrease P loss by optimizing agricultural nutrient usage, some fields continue to have elevated soil test phosphorus (STP) levels even when nutrients have not been applied for decades. These fields, referred to as legacy P fields, contain more P within the soil profile than agronomically necessary and have substantial nutrient runoff potential. Because these sites disproportionately contribute to nutrient runoff, it is important to determine what variables impact and how best to manage nutrient loss from legacy P fields. Rainfall depth and intensity have been identified as driving factors causing P runoff from fields within agronomic STP levels. Better knowledge of the impact of precipitation and temperature on runoff from legacy P fields will improve management to minimize nutrient loss from these unique settings. This is especially valuable information as production and water quality management adaptations are made in reaction to climate change. To determine how weather variability impacts P runoff from legacy P fields, water quality and water quantity data was collected at 11 fields with Mehlich-3 P STP > 100 mg/kg in northwest Ohio for a total of 18.5 site-years, during which time 477 storm events each with > 6.35 mm (0.25 in) of precipitation were monitored. This study found that average nutrient concentrations within tile discharge from legacy P fields were 2.4 times (total P; TP) and 4-5 times (dissolved reactive P; DRP) larger than the equivalent on fields with agronomically appropriate STP (i.e., agronomic fields). Additionally, legacy P fields behaved similarly to agronomic fields during precipitation events: rainfall amount was the primary climatic variable affecting TP and DRP loads while tile discharge and nitrate loads were both largely affected by rainfall amount and event duration. By addressing fundamental questions about interactions between elevated STP fields, climate, and nutrient transformation and transport, this study provides greater insight to the significance of legacy P fields on water quality issues and therefore informs decisions on BMP selection and design. Stacked BMPs on fields with high nutrient loss potential are hypothesized to improve quality of runoff more than non-targeted or single practices. To measure the effectiveness of stacked conservation practices on a legacy P field, this study analyzed nutrient loss from a western Ohio field for nearly two years. The targeted subsurface tile drained 4.5 ha (11.1 acres) of the field to the first BMP, a ditch-style P removal structure (PRS) filled with electric arc furnace steel slag. The effluent from the PRS then discharged into a second BMP: a constructed wetland. Discharge moving through the stacked practices was monitored with bubbler flow meters and area velocity sensors and water samples were collected using automated water samplers at the inflows and outflows of each BMP. Between the inlet and outlet of the PRS, there was a 27% reduction in TP concentration and an 18% increase in DRP concentration. The wetland produced statistically significant and consistent reductions of TP loading and DRP loading by 30% and 18%, respectively. Although the PRS did not perform as designed, the stacked PRS and wetland in series had overall load reductions of TP (36%) and DRP (18%). The analysis of these stacked practices demonstrates that although one of the two BMPs performed poorly, there is a benefit to redundant designs, which provides insight on how to best implement BMPs on agricultural lands.
Jay Martin (Advisor)
Ryan Winston (Committee Member)
Kevin King (Committee Member)
133 p.
Agricultural Engineering
Nutrients; Phosphorus; Legacy Phosphorus; Climate; Stacked Practices; Wetland; Best Management Practices

Recommended Citations

Citations

  • Crow, R. L. (2022). Evaluating the Impacts of Climate and Stacked Conservation Practices on Nutrient Loss from Legacy Phosphorus Agricultural Fields [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650471341835724

    APA Style (7th edition)

  • Crow, Rachelle. Evaluating the Impacts of Climate and Stacked Conservation Practices on Nutrient Loss from Legacy Phosphorus Agricultural Fields. 2022. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1650471341835724.

    MLA Style (8th edition)

  • Crow, Rachelle. "Evaluating the Impacts of Climate and Stacked Conservation Practices on Nutrient Loss from Legacy Phosphorus Agricultural Fields." Master's thesis, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu1650471341835724

    Chicago Manual of Style (17th edition)

osu1650471341835724
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