Graduation Term

2024

Degree Name

Master of Science (MS)

Committee Chair

ERIC W PETERSON

Abstract

In the U.S. Midwest, where fertile soils with high water retention are prevalent, the installation of tile drainage networks have become a common practice to drain excess soil water, enhancing plant growth and increasing crop productivity. However, tile drainage networks coupled with the use of inorganic fertilizers have significant implications on water quality, contributing to eutrophication, leading to harmful algal blooms, and resulting in hypoxic conditions in surface water bodies. To mitigate excess nutrient exports to surface water bodies, edge-of-field practices have been introduced. One such practice is the saturated riparian buffer (SRB), which utilizes a diversion system to redirect tile drainage water from an agricultural field into a riparian buffer rather than directly discharging into a stream. As a best management practice, SRBs have been shown to reduce nitrate loads delivered to surface water by increasing the travel time of nutrient-rich waters through soils and exposing the nutrients to soil processes. This research examined six years (2015-2021) of data from an SRB to investigate trends in the nitrate as nitrogen (NO3-N) concentrations of the groundwater upgradient (independent) of the diversion system as compared to waters downgradient (dependent) of the diversion system during tile flow and examined the duration of time the tile water influences the SRB. The analysis, using a mixed effect model (α=0.05), found no significant relationship between the volume of tile flow and NO3-N concentrations in both upgradient and downgradient groundwater during periods of tile flow from the day of sampling up to five weeks prior before sampling. The lack of immediate effect on the day of sampling from the volume of tile flow on NO3-N concentrations was attributed to the travel time required for water to move from diversion tiles to groundwater. Further, the lack of influence of the volume of tile flow on NO3-N concentrations observed five weeks prior reinforces previous findings by indicating a loss of NO3-N within the system. Although the volume of tile flow did not alter the NO3-N concentration, it did have a positive impact on chloride concentration in the downgradient groundwater. Given the conservative nature of chloride, these differences in response suggests that the lack of an observed increase in NO3-N concentrations wase due to losses within the system, likely from removal mechanisms. On a year-to-year basis, NO3-N concentrations within the SRB remained similar during periods of no tile flow, indicating that there was not a long-term accumulation within SRB. The consistency of NO3-N concentrations observed during periods of no tile flow affirms the SRB’s role in managing NO3-N concentration through soil processes.

Access Type

Thesis-Open Access

DOI

https://doi.org/10.30707/ETD2024.20240827063555888157.1000000

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