Minor effects of no-till treatment on GHG emissions of boreal cultivated peat soil

Greenhouse gas emissions of a spring cereal monoculture under conventional tillage and no-till treatments were measured in a peatland in Southwestern Finland for three years in 2018-2021. Nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) fluxes were measured with an opaque chamber technique approximately biweekly throughout the years. During the growing season, canopy net ecosystem exchange (NEE) was measured with a transparent chamber technique and hourly ecosystem respiration (ER) and gross photosynthesis (GP) were modelled with empiric models. On average, the annual emissions were 6.4±2.4 Mg CO2-C ha ^-1 yr^-1, 7.6±3.5 kg N2O-N ha^-1 yr^-1, and -0.35±0.42 kg CH4-C ha^-1 yr^-1 for NEE, N2O and CH4, respectively. The effect of no-till management on the GHG balance was non-consistent through years and thus generally of minor significance. No-till reduced annual CO2 emissions by 24% in 2019 and N2O emissions by 33% in 2020 compared to conventional tillage while there were no differences in other years. Measured differences in ER occurred mostly during the winter periods, especially after ploughing. The results indicated that no-till may reduce CO2 and N2O emissions from cultivated peat soil, but it does not lead to large consistent reductions during the first years of NT management.