Emission of the greenhouse gas nitrous oxide (N2O) from riparian forest buffers, warm-season and cool-season grass filters and crop fields.

Emission of the greenhouse gas nitrous oxide (N2O) from riparian forest buffers, warm-season and cool-season grass filters and crop fields.

Summary

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.

Objectives/Performance Targets

This study will answer the following questions: 1) How do denitrification rates differ between different kinds of riparian buffer vegetation and adjacent crop fields in the same soil mapping units? 2) Do different kinds of riparian buffer vegetation produce different amounts of N2 and N2O? 3) Are riparian buffers a more significant source of N2O than adjacent crop fields?

Results from this study will estimate how much harmless N2 and potentially harmful N2O is being emitted by denitrification from riparian forest buffers, warm- season and cool- season grass filters and crop fields. The results will help develop buffer design criteria that address emission of these two gasses. Results will be presented at scientific meetings such as the American Society of Agronomy/Crop Science Society of America/Soil Science Society of America and the Soil and Water Conservation Society. The audience at these meetings comes from a broad national base of scientists and professionals who are interested in sustaining and improving the environmental quality of the agroecosystem. Informing these audiences of the results, should stimulate further research in other regions of the country. A scientific paper will be prepared for publication in either the Soil Science Society of America Journal or the Journal of Environmental Quality and another more applied paper for publication in the Journal of Soil and Water Conservation. These publications will reach even larger audiences of scientists and professionals. We will also prepare a new or modify an existing extension bulletin on buffer design to incorporate the new information. Results of this work will also provide greenhouse gas modelers with another data set of field measures on both quantities of gases emitted and process rates that will help refine the predictions of these models for the Midwest. Finally, the results will provide additional supporting information to the public and to policy makers on the benefits of riparian buffers as one of the most effective tools for coping with non point source pollution caused by agricultural activities.

Accomplishments/Milestones

Nothing to report at this time.

Impacts and Contributions/Outcomes

Kim, D., Schultz, R.C., Isenhart, T.M., Parkin, T.B., Raich, J.W., Loynachan, T.E. 2006. Flux of dissolved N2O in groundwater from crop field to riparian buffers. In: Soil and Water Conservation Society workshop, Managing Agricultural Landscapes for Environmental Quality: Strengthening the Science Base, October 11-13, 2006. Kansas City, MO.

Kim, D., Schultz, R.C., Isenhart, T.M., Simpkins, W., Parkin, T.B., Raich, J.W., Loynachan, T.E. 2006. Emission of the Greenhouse Gas Nitrous Oxide (N2O) from Riparian Forest Buffers, Warm-Season and Cool-Season Grass Filters and Crop Fields. In: ASA-CSSA-SSSA Annual Meeting, Nov. 12-16, 2006, Indianapolis, IN.

Kim, D., Schultz, R.C., Isenhart, T.M., Simpkins, W., Parkin, T.B., Raich, J.W., Loynachan, T.E. 2006. Emission of the Greenhouse Gas Nitrous Oxide (N2O) from Riparian Forest Buffers, Warm-Season and Cool-Season Grass Filters and Crop Fields. In: 4th USDA Greenhouse Gas Symposium, Feb. 6-8, 2007, Baltimore, MD.