Influence of water management on GHG-balances along a land use intensity gradient in fen peatlands

This study examined the impact of different water management (WM) strategies and farming practices on greenhouse gas (GHG) emissions from organic soils at two sites in Southern Germany—the Altbayerisches Donaumoos and the Freisinger Moos. The aim was to assess whether specific WM and land-use measures could stabilize water tables and reduce CO₂, CH₄, and N₂O emissions, while maintaining agricultural productivity.

In our test site in the Altbayerisches Donaumoos (arable land growing grain maize under conventional and organic management), four field treatments were established: two with controlled WM via subsurface irrigation and two reference sites without active WM. Results from 2022 showed reduced total GHG emissions—mainly driven by lower CO₂ and N₂O fluxes—on the WM plots compared to references, especially under organic management. CH₄ fluxes were negligible, indicating a minor effect on the overall budget.

In the test site Freisinger Moos (grassland with three cuts per year), four treatments (two with subsurface irrigation at 30 and 50 cm depth, one with a simple raised water table through a weir, and one “pipe-less” subsurface system) were monitored during 2022 and 2023. Despite generally higher water tables in the irrigated plots, both CO₂ and N₂O emissions remained substantial. The 50 cm subsurface irrigation consistently showed the highest GHG fluxes, partly due to more intensive management and greater biomass exports. Notably, all treatments displayed increased emissions in 2023 compared to 2022—a rise attributed to possible changes in water availability, climatic factors, and residual effects of organic fertilization.

These findings highlight the complexity of balancing water management, agriculture, and climate protection in peatland regions. While raising the water table can reduce peat decomposition, achieving significant mitigation requires careful consideration of fertilizer inputs, crop type, and long-term soil conditions. While water management did have an effect on reducing CO₂ emissions, this is not yet sufficient to be seen as a climate friendly practice. Future research should address long-term impacts and refine water-level targets to further optimize land use on organic soils and mitigate associated greenhouse gas emissions.