Abstract. The objectives of this study were (1) to determine the effects of land use change on N oxide fluxes from soil in seasonally dry, eastern Amazonia and (2) evaluate the "hole-in-the-pipe" model in a field setting where N availability varies among land uses and soil moisture varies among seasons. We measured N oxide flux from an old-growth forest, a 20-year-old secondary forest, an active pasture, and a degraded pasture. We also measured soil water content, soil inorganic N stocks, net N mineralization and nitrification potential. To determine the effects of pasture age on N oxide flux, we measured gas fluxes at a chronosequence of pastures (0-13 years).In the land use study, N20 fluxes followed the order: primary forest (