Timing of grass renewal regulates nitrous oxide emissions from a drained boreal peatland

Abstract

Drained peatlands in northern latitudes have been used for forage production for decades. They are recognized sources of nitrous oxide (N2O) emissions. In boreal regions, grassland renewal is mandatory to maintain high forage productivity and quality, yet renewal practices involving ploughing can significantly increase N2O emissions. Here, we assessed the effect of plough timing (autumn ploughing with spring reseeding (AP) vs summer ploughing with immediate reseeding (SP)) on N2O emissions from a drained peatland in Eastern Finland. We conducted a three-year field experiment measuring N2O fluxes using manual chambers during snow-free seasons and snow gradient method during the snow-covered periods. Results showed that AP (88 kg N2O-N ha−1) emitted 2.6 times more N2O than SP (34.5 kg N2O-N ha−1) over the three years and exhibited greater interannual variability in its N2O emissions. Ploughing in the autumn led to sustained higher N2O emissions for longer periods and affected the following non-growing season and annual emissions considerably. Similarly, three-year yield-scaled N2O emissions were 2.2 times more in AP (3.7 kg N Mg−1) than in SP (1.7 kg N Mg−1). We found that grassland renewal increased the yield compared to the yields prior to renewal. These findings suggest that summer ploughing with prompt reseeding is a more sustainable practice for grassland renewal on drained peatlands, offering reduced N2O emissions without compromising productivity.