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UBC Theses and Dissertations
The effects of diversion terraces, grassed waterways, and tile drainage on selected soil properties and greenhouse gas emissions Driscoll, Bryan Andrew
New Brunswick is one of the largest potato producing regions in Canada, which has experienced soil erosion and a decline in soil health due to intensive tillage from potato production. To address these concerns and the uncertainties of temperature and precipitation pattern changes from climate change, a new system has been proposed for soil and water conservation in Atlantic Canada. The landscape integrated soil and water conservation (LISWC) system combines diversion terraces, grassed waterways, tile drainage, water retention structures, supplemental irrigation, conservation tillage, and soil-landscape restoration. The objective was to evaluate the effects of diversion terraces, grassed waterways, and tile drainage relative to contour tillage on selected soil properties and greenhouse gas emissions over the initial three seasons of management implementation. The study site consisted of three land management practices (LMPs): contour tillage (CT), diversion terraces and grassed waterways (DTGW), and diversion terraces, grassed waterways, and tile drainage (DTGW+TD). Aggregate stability decreased in all LMPs, and LMP had a significant effect on labile carbon (POXC). CT led to a decrease of 11.2% POXC over the study period, while DTGW increased 19.8% and DTGW+TD increased 50.6%. Mineral associated organic matter (MAOM) carbon was affected by LMP: CT carbon concentrations decreased 3.75%, while DTGW+TD rose 9.7% and DTGW rose 15.8%. I also conducted a short-term incubation experiment in February of 2021 to quantify greenhouse gas fluxes in response to volumetric water content (20%, 27%, 35%, and 40%), nitrogen fertilizer application rates (0 and 170 kg N ha-1), and temperature (10°C and 25°C). Overall, both DTGW and DTGW+TD offer potential for improvement of soil health, relative to CT, in the second and third years of implementation, with increases in the labile C fraction POXC, a fraction significantly related to SOC, and increases in MAOM. This is the first study in the area measuring GHG emissions from erosion control structures. This study demonstrated that DTGW+TD significantly reduced the loss of CO₂ relative to DTGW, while also not emitting significantly more than CT, in the three years after implementation. Results were similar with respect to loss of nitrogen as N₂O.
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