Date of Award
8-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Plant and Environmental Science
Committee Chair/Advisor
Rongzhong Ye
Committee Member
William Bridges
Committee Member
Thomas O'Halloran
Committee Member
Sean Schaeffer
Abstract
The soils of South Carolina are sandy and highly weathered, which leads to low nutrient availability and poor productivity without fertilizer application. Organic production is known for greater sustainability, but it faces additional challenges on these soils due to lower observed yields and limited fertilizer options. Cover crops (CCs) are a common practice for building organic matter and retaining soil nutrients. However, information on CC effects on soil properties under organic production in sandy soils is limited, and research has linked soil benefits to CC biomass. Furthermore, information on how CCs interact with other common conservation management practices (i.e., organic N amendments, conservation tillage) is also limited. To address these issues, four studies were conducted: 1) a model was developed to estimate CC biomass based on different CC planting and termination scenarios, 2) a 90-day field study was developed to measure the loss and uptake pathways from decomposition of 15N labeled hairy vetch application in cucumber production to determine the fate of CC-N, 3) a two-year field study was conducted to measure soil greenhouse gas (GHG) emissions under integrated management practices to assess practices effects on sustainability, and 4) a 60-day incubation study was performed to evaluate soil priming responses to increasing inputs of 13C labeled hairy vetch and cereal rye residue. This research demonstrates that CC biomass on the sandy soils of South Carolina can be accurately predicted using heat units, thereby providing producers with better estimations of CC-N credits. 15N analysis showed that legume CCs may act as an adequate N source with minimal N2O production. Furthermore, biomass inputs from the CC mix did increase CO2 emissions compared to fallow, but environmental impacts decreased when combined with other conservation management practices. Lastly, 13C analysis showed that legume CCs can accelerate SOM decomposition in sandy soils, especially with increasing residue inputs.
Recommended Citation
Oliver, Frank E., "Soil Carbon and Nitrogen Cycling in Organically Managed Sandy Soils under Cover Crop-Based Conservation Management" (2026). All Dissertations. 4317.
https://open.clemson.edu/all_dissertations/4317