ORCID
0009-0008-8272-3734
Date of Award
2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Natural Resources
First Advisor
E. C. Adair
Abstract
Agricultural soils are sources of nitrous oxide (N2O) and methane (CH4), two potentgreenhouse gases (GHG). Soil management practices, topographic position, and environmental factors can influence the magnitude of GHG emissions, yet few studies have investigated how these factors interact. Because soil conditions vary across topographic gradients and extreme weather events are becoming more frequent, interactions among management, landscape position, and climate may amplify or mitigate GHG emissions. This thesis investigates how agricultural soil management practices and topographic variation influence N2O and CH4 emissions in both field conditions and a controlled laboratory setting. In Chapter One, we conducted a 17-month study across a 21-hectare corn silage field in Vermont, measuring GHG emissions, inorganic nitrogen availability, and environmental conditions across three different management systems (business-as-usual, a soil health management system, and a novel manure- derived amendment). Each treatment contained topographically high and low plots. We found that emissions varied strongly by topography, with low-lying areas consistently producing greater N2O and CH4 emissions, especially in the soil health management system. These patterns were driven primarily by increased soil moisture, inorganic nitrogen, and labile carbon in low areas. In Chapter Two, we conducted a 40-day incubation where we applied identical soil moisture treatments to intact soil cores collected from topographically high and low plots, removing soil moisture as the differentiating factor between these positions. GHGs were measured every other day and inorganic nitrogen was extracted from soil samples at the start and end of the experiment. In contrast to the field results, high topography soils emitted substantially more N2O and CH4 under all moisture regimes. These soils also had higher inorganic nitrogen and microbial respiration rates, suggesting that available nutrient status and microbial communities strongly influenced emissions. Together, these studies demonstrate that soil moisture is a key environmental trigger for GHG emissions in the field, but that underlying soil properties shaped by topography and management determine the magnitude and trajectory of those emissions. This thesis advances our understanding of how N2O and CH4 emission behave under field and controlled conditions, and highlights the importance of considering spatial variability and hydrologic context when evaluating the climate impacts of agricultural management practices.
Language
en
Number of Pages
87 p.
Recommended Citation
Ratliff, Molly, "Greenhouse Gas Emissions from Agricultural Soils are Shaped by Management and Topography in a Changing Climate" (2025). Graduate College Dissertations and Theses. 2092.
https://scholarworks.uvm.edu/graddis/2092