Soil Carbon Dioxide Fluxes from Conventional and No-Tillage Small-Grain Cropping Systems
1996
Fortin, M.-C. | Rochette, P. | Pattey, E.
Conversion to conservation tillage systems increases soil C content by reducing soil erosion and the rate of organic matter oxidation. We hypothesized that these effects could impact soil emission of CO₂. This study (i) determined if CO₂ emissions were reduced in the first years after conversion to no-tillage (NT) relative to conventional tillage (CT), (ii) evaluated whether differences in soil CO₂ emissions between tillage treatments were related to soil temperature differences, and (iii) determined if soil CO₂ emission measurements provided an early estimate of soil management practice impact on soil organic C. In 1992 and 1993, CT and NT plots were planted to small-grain cereals in Ottawa, Ontario, on a Dalhousie silt loam (mixed, mesic, Typic Endoaquoll). Fluxes were measured using closed chambers connected to a portable CO₂ analyzer. During growing season 1992, the CO₂ emissions varied from 0.05 to 0.18 mg CO₂ m⁻² s⁻¹ with an average of 0.12 mg CO₂ m⁻² s⁻¹ for CT and of 0.10 mg CO₂ m⁻² s⁻¹ for NT. In 1993, the CO₂ emissions varied from 0.06 to 0.35 mg CO₂ m⁻² s⁻¹ with an average of 0.15 mg CO₂ m⁻² s⁻¹ in both tillage treatments. Differences in soil CO₂ fluxes between treatments were related to differences in soil temperature (r² = 0.62), giving an estimate of 75 g C m⁻² yr⁻¹ difference in organic C transfers to the atmosphere between CT and NT. These results were validated using an independent estimation derived from long-term field experiments. Thus, soil CO₂ flux measurements using dynamic closed chambers can provide early estimates of soil management impacts on soil organic C. Contribution no. 95-58.
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