Comparison of indirect nitrous oxide emission through lysimeter drainage between an Andosol upland field and a Fluvisol paddy field

Indirect emission of nitrous oxide (N2O) due to nitrogen (N) leaching and runoff from agricultural soils is a major source of atmospheric N2O. To evaluate the effect of agricultural land use in combination with soil type on indirect N2O emission through groundwater, we compared the indirect N2O emission between an upland field of Andosol and a paddy field of Fluvisol in a 1-year lysimeter experiment. We established a shallow groundwater table during the non-flooded fallow period in the Fluvisol paddy field to simulate moisture conditions in a lowland soil. Drainage was 795 mm yr (median, n=6) in the Andosol upland field, versus 1583 mm yr(-1) in the Fluvisol paddy field due to flooding during part of the year. The total leached nitrate in the Andosol upland field (4.24 g N m-2 yr(-1)) was comparable to that in the Fluvisol paddy field (5.57 g N m(-2)yr(-1)). The total indirect N2O emission in the Fluvisol paddy field (88.6 mg N m(-2) yr(-1)) was 55 times that in the Andosol upland field (1.62 mg N m(-2) yr(-1)). The daily indirect N2O emission during the flooded period (0.239 mg N m(-2)d(-1)) was comparable to that in the non-flooded period (0.156 mg N m(-2) d(-1)) in the Fluvisol paddy field. The decrease in dissolved N2O concentration due to the flooding was offset by the increase in the drainage volume. The groundwater emission factors (EFsg) were 0.0003 in the Andosol upland field and 0.0160 in the Fluvisol paddy field versus the IPCC default value of 0.0025. Although the lysimeters had some limitations to simulate actual field conditions, the results indicate that agricultural land use in combination with soil type can strongly affect indirect N2O emission through groundwater.