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Resque Porto, Paula

University of British Columbia

An observational study was conducted to investigate the potential of managing field hydrology to reduce soil greenhouse gas emissions (GHG) from blueberry crop rows on silt loam soils in a temperate maritime climate. Results from the field study were used to validate three models: the tier 1 IPCC and tier 2 equation by Rochette et al. (2018), which are used to estimate annual soil nitrous oxide (N₂O) emissions, and the tier 3 Denitrification-Decomposition model (DNDC) which simulates daily soil emissions of carbon dioxide (CO₂), N₂O, and methane (CH₄). Soil emissions were measured every two weeks for two years, using dynamic closed chambers in nine fields, which were either (1) undrained, (2) drained with subsurface tiles, or (3) drained with subsurface tiles and ditch pumps. Drainage system did not impact field hydrology or soil GHG emissions; thus, the fields were recategorized using principal component analysis according to their two-year mean water table (WT) level and soil volumetric water content. On average, fields with higher WT levels emitted significantly more CO₂ and N₂O, by 29% and 130% respectively, resulting in higher overall annual emissions (36,095 kg CO₂eq ha⁻¹ year⁻¹ versus 28,755 kg CO₂eq ha⁻¹ year⁻¹ in lower WT fields). High WT fields emitted more CO₂ in the spring and summer, and more N₂O in the fall and winter. Stepwise linear regressions showed that soil temperature was the main driver of soil CO₂ emissions, but drivers were unclear for N₂O and CH₄ emissions. The DNDC model overestimated the effect of freeze-thaw events on soil CO₂ emissions, and underestimated soil N₂O emissions, especially in the shoulder season. Annual soil N₂O emissions were poorly estimated by all three models, but the equation by Rochette et al. (2018) provided the most accurate estimate of mean annual soil N₂O emissions, underestimating them by 6% compared to 89% and 90% with the IPCC and DNDC models, respectively. The results indicate that lowering the WT could reduce soil emissions in blueberry crop rows; but more information on net field GHG budgets is needed before recommending drainage as a GHG mitigation practice for silt loam soils in Delta, British Columbia.

Text

2023-04-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84318

Soil Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/