Author ORCID Identifier

https://orcid.org/0000-0001-7285-7730

Year of Publication

2021

Degree Name

Master of Science in Biosystems and Agricultural Engineering (MSBiosyAgE)

Document Type

Master's Thesis

College

Agriculture; Engineering

Department/School/Program

Biosystems and Agricultural Engineering

First Advisor

Dr. William Ford

Abstract

In the Midwestern U.S. seasonal hypoxia experienced in the Gulf of Mexico and harmful algal blooms in inland freshwater ponds, lakes, and rivers are partly fueled by dissolved orthophosphate loadings from disturbed landscapes. Efforts to reduce dissolved reactive phosphate (DRP) loadings have had varying levels of success and have led to insufficient water quality improvements. Inefficiencies in conservation strategies can stem from poor understanding of phosphate source and flow pathway dynamics. This study focused on monitoring sources and flow pathways of dissolved reactive P in a karst agroecosystem with phosphatic limestone. We collected event water samples at the Camden Creek watershed outlet in Woodford County, Kentucky and characterized P sources by sampling spring water and soils across the watershed. Oxygen isotope results for orthophosphate at springs suggested significant differences in isotope signatures at high and low flows, despite similar concentrations, likely reflecting differences in connectivity to anthropogenic and ambient P sources. Multiple linear regression models to predict DRP concentrations revealed that a mass-balance unmixing approach may help distinguish between DRP pathways in a heterogeneous karst system better than commonly used hydrograph recession methods. Soils from our study site had high extractable P concentrations at both the surface and deeper soil zones, with high heterogeneity reflecting soil composition and spatial variability in management. Overall, this work provides insight into phosphate source and transport in a karst agroecosystem and provides broader implications for implementing best management strategies to reduce DRP loading in such systems.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.344

Available for download on Saturday, February 12, 2022

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