The impact of ploughing intensively managed temperate grasslands on N2O, CH4 and CO2 fluxes

Background and aims: Temperate grasslands are a globally important component of agricultural production systems and a major contributor to the exchange of greenhouse gases (GHG) between the biosphere and atmosphere. Many intensively managed grazed grasslands in NW Europe are ploughed and reseeded occasionally in order to improve their productivity. Here, we examined the impact of ploughing on the emission of GHGs a grassland. Methods: To study these interactions we measured soil GHG fluxes using the static chamber method in addition to the net ecosystem exchange (NEE) of CO2 by eddy covariance from two adjacent fields. Until ploughing one field in 2012 and the other in 2014, management of these intensively grazed grasslands was almost the same and typical for the study region. Results: The effect on N2O is small, but distinguishable from the effects of N fertilisation, soil temperature and soil moisture. Tillage-induced N2O fluxeswere close to expectations based on the IPCC default methodology. By far the dominant effect on the GHG balance was the temporary reduction in GPP. Conclusions: Ploughing and reseeding can substantially influence short-term GHG emissions. Therefore tillageinduced fluxes ought to be considered when estimating greenhouse gas fluxes or budgets from grasslands that are periodically ploughed.