Thesis
Into the deep: Effects of agricultural management practice on deep soil carbon dioxide
Washington State University
Master of Science (MS), Washington State University
Spring 2020
DOI:
https://doi.org/10.7273/000004035
Handle:
https://hdl.handle.net/2376/125308
Abstract
Sustainable agricultural methods must be identified and practiced in order to ensure food security for a growing global population while also mitigating the effects of climate change. Organic agriculture commonly supports more surface soil organic carbon (SOC) than conventional agriculture. However, it is unclear whether organically managed soil profiles act as a net sink or source of carbon dioxide (CO2), a major greenhouse gas. Little is known about the role of soil CO2 in carbon sequestration and CO2 emission to the atmosphere in organically managed soils. In a replicated study on Palouse silt loam soils we found that CO2 concentrations were greater in organically managed soils than in conventionally managed soils at depths down to 1.5m throughout the year, particularly during the growing season. In the organically managed system, the CO2 concentration between 30-150 cm averaged across depth and time was over 23,000ppm, and just under 7,000ppm for the conventionally managed system. The greater concentrations in the organic system were primarily the result of greater CO2 production at 60cm. Carbon dioxide (CO2) as gas and dissolved into soil water comprises only 0.22% of total C stocks in the organic system and less than half that in the conventional system, but its agency within the soil C cycle may be critical. Elevated CO2 in the soil depresses microbial oxidation of SOC, preserving soil SOC stocks, and drives greater rates of chemical weathering, which is a long-term pathway for CO2 sequestration in the hydrosphere and lithosphere. These results demonstrate that organic agriculture may remove additional C from the atmosphere via enhanced deep soil respiration, and chemical weathering processes, which leads to greater total rates of carbon sequestration than conventionally estimated.
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Details
- Title
- Into the deep
- Creators
- Summer Rose Ann Lockhart
- Contributors
- Chester Kent Keller (Chair) - Washington State University, School of the Environment (CAS)Lynne Alane Carpenter-Boggs (Committee Member) - Washington State University, Department of Crop and Soil SciencesRaymond David Evans (Committee Member) - Washington State University, School of Biological SciencesAlex Fremier (Committee Member) - Washington State University, School of the Environment (CAS)
- Awarding Institution
- Washington State University
- Academic Unit
- School of the Environment (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890794501842
- Language
- English
- Resource Type
- Thesis