Denitrification is recognized as the major mechanism for reducing nitrate in riparian buffers and thus diminishing non-point source pollution (NPS) of surface water bodies subject to high nitrogen loads. However, increasing denitrification rates in riparian buffers may be trading the problem of NPS pollution of surface waters for atmospheric deterioration and increased global warming potential because denitrification produces nitrous oxide (N2O), a greenhouse gas also involved in stratospheric ozone depletion. It is therefore important to quantify the emissions of N2O from different kinds of vegetated riparian buffer systems, and to identify ways to reduce those emissions while simultaneously maximizing denitrification. We measured denitrification rates, N2O emissions from soils, N2O/ N2 emission ratios, nitrate (NO3-), N2O in groundwater, and soil properties in riparian forest buffers, warm-season and cool-season grass filters, and a crop field located in the Bear Creek watershed in central Iowa. Preliminary results suggest that amounts of N2O emissions from soils in all riparian buffers were significantly less than in the crop field, but no differences among different kinds of riparian buffers were observed. Nitrate in outflow groundwater of riparian buffers was significantly lower than in inflow groundwater of riparian buffers. However, dissolved N2O in inflow and outflow groundwater of riparian buffers were not significantly different from one another. In this presentation, we will discuss peak N2O emissions from soils, which follow the thawing of frozen soils, the application of fertilizer and tillage; and negative N2O fluxes that are observed in late fall to early spring from all systems. Annual N2O emissions from soils and dissolved N2O in groundwater, N2O/ N2 emission ratios, and denitrification rates from the sites also will be presented.