Replication Data for Raw data for the publication: Impact of drain spacing on subsurface drainage and greenhouse gas fluxes in a grassland on a sandy silt soil in western Norway.

We established drainage systems with 6 and 12 m drain spacing in a previously undrained sandy silt under grass. Subsurface drainage was larger (1415 versus 520 mm) and ground water table (GWT) was lower (102 versus 79 cm) with 6 than with 12 m drain spacing. Water filled pore space values (WFPS) remained high throughout most of the year (> 80%). Most N2O emissions occurred shortly after fertilization in 12 m system whereas emissions from 6m occurred throughout the year. Cumulative N2O emissions in the 6 and 12 m system were 4.0 versus 2.5 kg N ha-2 yr-1. Grass yields, plant N-recovery and fertilizer N use efficiency was larger with 6 than 12 m drain spacing and there was no difference in yield-scaled N2O emissions (0.26 mg N2O-N kg DM-1). The mean N2O emission factor was significantly higher with 6 than with 12 m drain spacing (1.4 versus 0.8 % N2O-N of N applied). The 6 m system acted as a net sink for CH4, whereas the 12 m system was a net CH4 source. N2O emissions dominated the non-CO2 global warming potential (GWP). The 6 m system had a higher GWP than the 12 m system (1390 versus 1110 g CO2 eq. m-2 yr-1). We conclude that higher observed N2O emissions at 6 m were likely due to a combination of less complete denitrification and a higher release of N from SOM at this site. Our study does not confirm that increased drainage intensity intrinsically reduces N2O emissions.