- Additional Plants: native plants, ornamentals, trees
- Crop Production: agroforestry, forestry, nutrient cycling
- Education and Training: decision support system, demonstration
- Natural Resources/Environment: riparian buffers, riverbank protection
- Production Systems: agroecosystems, holistic management
- Soil Management: nutrient mineralization, organic matter, soil analysis, soil quality/health
Denitrification is recognized as the major mechanism for reducing nitrate in riparian buffers coping with non-point source pollution (NPS) of surface water bodies. However, there are still questions about the quantity and products of denitrification that different kinds of riparian buffer vegetation can support. It has recently been hypothesized that the increased denitrification rates in riparian buffers may be trading the problem of NPS pollution of surface waters for atmospheric deterioration and global warming problems because denitrification produces both nitrogen gas (N2) and nitrous oxide (N2O) a greenhouse gas also involved in ozone depletion. It is therefore important to compare the effects of different kinds of riparian buffer vegetation on the production of N2 and N2O from the denitrification process. This study will attempt to answer the following questions: 1) How do denitrification rates differ between various kinds of riparian buffer vegetation and adjacent crop fields in the same soil mapping units? 2) Do different kinds of riparian buffer vegetation produce varying amounts of N2 and N2O? 3) Are riparian buffers a more significant source of N2O than adjacent crop fields? This research will be conducted in riparian forest buffers, warm-season and cool-season grass filters, and a crop field all located in the Bear Creek watershed in central Iowa. Denitrification rates, N2O emission, N2O in groundwater, N2O/ N2 emission ratio and soil properties will be measured regularly and the data will be applied to models to simulate N2 and N2O emission from the sites. The results may stimulate additional research and will provide farmers and professionals with modified buffer design criteria that consider the impact of riparian vegetation on denitrification and N2 and N2O emission. Finally, this work will help policy makers and the public further accept the different kinds of riparian buffers as effective tools to improve agroecosystems and minimize the potential impact on global warming and ozone depletion.
Project objectives from proposal:
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.