Groundwater-induced emissions of nitrous oxide through the soil surface and from subsurface drainage in an Andosol upland field: A monolith lysimeter study

Nitrous oxide (N2O) produced in shallow groundwater has two emission pathways to the atmosphere: dissolution in subsurface drainage and groundwater and later degassing from water surfaces open to the atmosphere, and upward gas diffusion. N2O undergoing upward diffusion through the soil surface cannot usually be distinguished from N2O produced in the topsoil. To evaluate the emission pathway and rate of groundwater-induced N2O, we conducted a one-year experiment using monolith lysimeters containing 1 m-long undisturbed Andosol. We measured emission of N2O via the soil surface and dissolved N2O emitted via subsurface drainage from the non-planted lysimeters under two conditions without fertilizer-nitrogen (N) addition: (1) with the groundwater table at 0.9 m depth (GW), and (2) without any groundwater table (nonGW). Total soil surface N2O emissions in the GW and nonGW treatments were 21.0 ± 6.3 and 17.0 ± 1.1 mg N m–2 yr–1, respectively (mean ± standard error, n = 3), and the difference between the two trea...