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

Abstract

The greenhouse gas (GHG) emissions of spring cereal monoculture under long-term conventional tillage (CT) and no-till (NT) treatment established in 2018 were measured in a peatland in Southwestern Finland during the period 2018–2021. Nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) fluxes were measured with chambers approximately every two weeks throughout the period under study. Net ecosystem exchange was measured during the growing seasons, and hourly ecosystem respiration (ER) and gross photosynthesis (GP) were modelled with empirical models. Across the whole period, annual emissions were 6.8 ± 1.2 and 5.7 ± 1.2 Mg CO₂–C ha ⁻¹ yr⁻¹ (net ecosystem carbon balance), 8.8 ± 2.0 and 7.1 ± 2.0 kg N₂O–N ha⁻¹ yr⁻¹, and − 0.43 ± 0.31 and − 0.40 ± 0.31 kg CH₄-C ha⁻¹ yr⁻¹ for CT and NT, respectively. The global warming potential was lower in NT (p = 0.045), and it ranged from 26 to 34 Mg CO₂ eq. ha⁻¹ yr⁻¹ in CT and from 19 to 31 Mg CO₂ eq. ha⁻¹ yr⁻¹ in NT. The management effect on the rates of single GHGs was not consistent over the years. Higher GP was found in CT in 2019 and in NT in 2020. Differences in ER between treatments occurred mostly outside the growing season, especially after ploughing, but the annual rates did not differ statistically. NT reduced the N₂O emissions by 31% compared to CT in 2020 (p = 0.044) while there were no differences between the treatments in other years. The results indicate that NT may have potential to reduce slightly CO₂ and N₂O emissions from cultivated peat soil, but the results originate from the first three years after a management change from CT to NT, and there is still a lack of long-term results on NT on cultivated peat soils.