PNNL

Abstract

Nitrous oxide fluxes from soils are inherently variable in time and space. An improved understanding of this variability is needed for accurate estimation of N2O fluxes at regional scale. We measured N2O fluxes and collected ancillary data (mineral N, water soluble C, soil water content, soil temperature) at two locations in Canada: Mundare (AB) and Swift Current (SK). At Mundare, measurements were taken in 1995 and 1996 by landscape position and land use. At Swift Current, data were collected in 1999 and 2000 by landscape position and N rate. At Mundare, landscape position affected N2O emissions but the pattern varied seasonally. During a 46 d period in summer 1995, N2O-N flux from a backslope (0.043 g m-2) was greater than fluxes arising from three other positions (0.007 g m-2). The pattern changed during a 43 d spring thaw of 1996 when fluxes from depressional areas were greatest (0.171 g m-2). N2O emissions from natural areas were small. The emission pattern during summer 1996 was similar to that of 1995 but the fluxes were an order of magnitude larger. At Swift Current, N2O fluxes in summer 1999 were affected by topography and N rate. Fluxes were greatest in depressional areas receiving N at 110 k ha-1 (0.314 g m-2). Use of the area fraction occupied by each landscape position to calculate N2O flux increased the estimates of N2O fluxes at the field scale by 10-14%.