Dong-Gill Kim1, Richard C. Schultz1, Thomas M. Isenhart1, Tim B. Parkin2, and Thomas E. Loynachan1. (1) Iowa State University, 339 Science 2, Ames, IA 50011-3221, (2) National Soil Tilth Laboratory, 2150 Pammel Drive, Ames, IA 50011-4420
Denitrification is recognized as the major mechanism for reducing nitrate in riparian buffers coping with non-point source pollution (NPS) of surface water bodies. It recently has been argued that increased 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 emission of N2O from different kinds of buffer systems and to identify ways to reduce those emissions. We measured denitrification rates, N2O emission, N2O/ N2 emission ratios, 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 N2O emission in all riparian buffers was significantly less than in the crop field and that amounts of N2O in different kinds of riparian buffer vegetation were not significantly different. Groundwater exported to the creek from riparian buffers was not a significant source of dissolved N2O. In this presentation, we will discuss annual N2O emissions, N2O/ N2 emission ratios, and denitrification rates from riparian forest buffers, warm-season and cool-season grass filters, and crop fields.