Environmental impacts and mitigation options on cultivated peatland with shallow peat depth in northern Finland – NorPeat platform

Abstract

To use peatlands for agriculture or forestry, they need to be drained. Lowered water table and increased oxygen concentration in the soil profile alter soil biogeochemistry, enhancing peat decomposition and mineralization processes. After the drainage, peatland changes from carbon sink to carbon source into the atmosphere and watercourses. The drainage affects the greenhouse gas (GHG) fluxes and runoff water quality depending on soil nutrient status and the new water table depth. Usually, carbon dioxide ad nitrous oxide fluxes increase, and methane fluxes decrease.In Finland, approximately 10% of cultivated fields are on organic soils but they are responsible for a larger share of agricultural GHG emissions. Finland has set a challenging goal for carbon neutrality by 2035, thus the pressure to mitigate GHG emissions from cultivated peatlands is high. However, if the cultivation of drained peatlands was heavily restricted, their local importance creates socio-economic challenges, due to their uneven distribution in Finland. At the same time, recent global and economic circumstances as well as the increased occurrence of extreme weather events have underlined the importance of national food security. During dry growing seasons, cultivated peatlands produce decent crop yields more reliably than mineral soils.NorPeat research platform (26 ha) located at Ruukki, Finland (64.68°N, 25.11°E) and governed by Natural Resources Institute Finland (Luke) is a cultivated peatland under normal silage grass rotation for beef cattle feed production. The platform was established in 2017 to study various environmental effects of cultivated peatlands monitoring year-round GHG fluxes, as well as flow and the quality of subsurface drainage water and overflow. The field is divided into 8 plots and the peat depth varies from 15 to 75 cm. Water storage reservoir (0.7 ha) located next to the field is connected to the subsurface drainage system and it allows subsurface irrigation and manipulation of the water table level in the individual plots. Environmental conditions are monitored with multiple sensors to supplement the datasets of GHG emissions and leaching. Along with field experiments, we are running column experiments in controlled conditions in the laboratory to study environmental impacts in more detail. In addition, the technical usability of sub-irrigation systems as a tool for GHG mitigation via water table control is studied in the field and laboratory. These are carried out with the aim to add automated features to the system to optimize the operation of the sub-irrigation.