Greenhouse Gas Emissions From Western Canadian Agricultural Soils Under Long Term No till Management After Tillage Reversal.

Tillage in combination with different fertilizer management regimes and environmental drivers (i.e., soil temperature and soil moisture) are likely to affect the greenhouse gas emissions of agricultural soils.  It is known that switching management from conventional tillage to notill can sequester carbon in the soil, but the stability and longevity of this newly sequestered carbon is unknown.  The present study aims at measuring growing season soil CO₂ and N₂O fluxes after tillage reversal on a Black Chernozemic soil at Ellerslie and a Grey Luvisolic soil at Breton, Alberta managed under long term no till.  We hypothesized that (i) tillage causes higher CO₂ emission by stimulating microbial decomposition through improved aeration (ii) tillage reduces N₂O emission by facilitating aerobic conditions that hinders the activities of denitrifying bacteria (iii) nitrogen fertilizer application stimulates CO₂ and N₂O emission from both till and no till plots through increased microbial growth and respiration. The study was further extended to explore the effects of soil type viz. organic matter rich Chernozem vs organic matter deficient Luvisol and environmental factors i.e. soil temperature and soil moisture. Our preliminary results showed that both total growing CO₂ and N₂O fluxes were higher from tilled and N fertilized plots of each soil type with an exception of the Luvisolic no tilled fertilized plots.  Average CO₂ fluxes were higher in tilled fertilized plots during 2010 than that in 2009 from black Chernozem as expected since in 2010 it received almost double precipitation of the previous year. This study has its significance in calculating carbon sequestration through changes in tillage regime as well as assessing contingency factors for both soil types to account for the possibility of isolated tillage events for weed control.