Soil Organic Carbon Sequestration Potential by Perennial Biomass Crops in Southern Ontario, Canada

Switchgrass (Panicum virgatum, SG) and Miscanthus (Miscanthus spp., Mis), C4 perennial biomass crops (PBCs), are being cultivated in Ontario, Canada, on degraded agricultural (Ag) fields to enhance soil organic carbon (SOC) sequestration. This study assessed SOC stocks in SG and Mis fields compared to baseline Ag SOC stocks at Elora, Guelph, and Burlington, using woodlot (WL) SOC as a reference. Results showed higher SOC stocks in SG, Mis and WLs than in baseline Ag fields. After 11 years, SOC stocks in Elora and Guelph PBCs were significantly higher, though Burlington showed no significant difference over 4 years. Nitrogen fertilizer rates did not significantly impact SOC in SG but increased SOC in Mis fields at specific rates. Converting marginal lands to PBCs can enhance SOC sequestration, aiding Canada’s climate goals. Additionally, this thesis compared SOC and soil total nitrogen (STN) levels in SG, Mis, Ag fields and WLs across different soil aggregate sizes at ten sites. Soil aggregates were categorized into macroaggregates (2000-250 μm), microaggregates (250-53 μm) and silt plus clay fractions (<53 μm). Higher SOC and STN concentrations were found in macroaggregates and silt plus clay fractions than in microaggregates. WLs had the highest SOC and STN concentrations in macroaggregates, followed by Mis, Ag and SG fields. STN stocks were highest in Mis fields. Using the 13C natural abundance technique, the proportion of C4-derived SOC in total SOC stocks was quantified, and sequestration rates were determined. After 11 years, C4-derived SOC accounted for 30% and 31% of total SOC in SG and Mis fields at Guelph, and 41% and 50% at Elora. After 4 years, C4-derived SOC was 10-12% in PBC fields and 17% in Ag fields at Burlington. C4-derived SOC sequestration rates at Guelph were 0.8, 0.7 and 0.4 Mg C ha-1 y-1 in SG, Mis and Ag fields, respectively. Mis fields had lower C4-derived SOC in macroaggregates but higher in microaggregates and silt plus clay fractions. Higher C4-derived SOC in macroaggregates in Ag fields suggests lower SOC stability. Cultivating SG and Mis on low-productive Ag lands could enhance SOC stability, supporting climate change mitigation.

Grantor dc:publisher

University of Guelph

Author dc:creator

• Vijayakumar, Sowthini

Advisors dc:contributor.advisor

• Thevathasan, Naresh
• Lauzon, John
• Voroney, Paul

• carbon sequestration
• soil organic carbon
• Switchgrass
• Miscanthus
• land use change

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10214/28474

OAI record oai:identifier

https://atrium.lib.uoguelph.ca/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aatrium.lib.uoguelph.ca%3A10214%2F28474