Determination of greenhouse gas sources and sinks in Swiss arable soils under organic and non-organic management

Agricultural practices contribute considerably to emissions of greenhouse gases (GHG). Knowledge on the impact of organic (ORG) compared to non-organic (NON-ORG) farming on soil-derived nitrous oxide (N2O) and methane (CH4) emissions is still limited. We conducted a literature search on measured soil GHG fluxes under ORG and NON-ORG from farming system comparisons and performed a meta-analysis. Based on 12 studies covering annual measurements, it appeared that area-scaled N2O emissions are with 14% significantly lower under ORG. However, yield-scaled N2O emissions are only 9% higher for ORG. Emissions from NON-ORG soils seemed to be influenced mainly by total N inputs, whereas for ORG other soil characteristics seemed to be more important because N2O from organic N fertilisers emits decoupled from the inputs. Furthermore, we observed a 12% higher CH4 uptake for arable soils under ORG.