Fluxes of nitrous oxide in tilled and no-tilled boreal arable soils

Agricultural management practices can have a significant effect on the emissions of nitrous oxide (N2O) from soils. The aim of this 2-year study was to investigate the effects of no-till (NT) and reduced tillage (RT) practices on annual fluxes of N2O from different soil types typical for the boreal region of northern Europe. We measured the fluxes of N2O in conventional tillage (CT) and NT at four sites of which two also had RT treatment. No-till and RT practices had been implemented 8–10 years before our study was initiated. Chamber measurements were carried out fortnightly in 2008–2010 on clayey (sites 1–3) and coarse (site 4) soils. Annual cumulative emissions of N2O varied from 2.4 to 8.3 in CT, 2.5–6.5 in RT and 4.9–10.2 kg N2O-N ha−1 in NT. High peaks in measured N2O fluxes occurred during and after thawing of the soil in April and after fertilization and high rain events. No-till or RT did not have any significant effects on soil C or N stocks or potential denitrification of the 0–20 cm soil layer. Dry bulk density and water-filled pore space (WFPS) were generally higher under NT compared to CT, most probably being the main reasons for the increased N2O emissions in the NT systems. Soil temperature varied less in NT by being higher during the colder periods of the year and slightly cooler during hot summer days. In conclusion, our results indicate that NT induces a risk of increased N2O emissions in clayey soils in small grain spring cereal agroecosystems in Northern European boreal climate.