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ARS Home » Midwest Area » Ames, Iowa » National Laboratory for Agriculture and The Environment » Agroecosystems Management Research » Research » Publications at this Location » Publication #354216

Research Project: Agroecosystem Benefits from the Development and Application of New Management Technologies in Agricultural Watersheds

Location: Agroecosystems Management Research

Title: Nitrous oxide emissions from saturated riparian buffers: Are we trading a water quality problem for an air quality problem?

Author
item DAVIS, MORGAN - Iowa State University
item GROH, TYLER - Iowa State University
item Jaynes, Dan
item Parkin, Timothy
item ISENHART, THOMAS - Iowa State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2018
Publication Date: 9/6/2018
Citation: Davis, M.P., Groh, T.A., Jaynes, D.B., Parkin, T.B., Isenhart, T.M. 2018. Nitrous oxide emissions from saturated riparian buffers: Are we trading a water quality problem for an air quality problem? Journal of Environmental Quality. 48(2):261-269. https://doi.org/10.2134/jeq2018.03.0127.
DOI: https://doi.org/10.2134/jeq2018.03.0127

Interpretive Summary: Nitrate in our Nation's surface waters can be detrimental for its use as a drinking water source and can cause excessive algal growth and "dead zones" in coastal waters such as the Gulf of Mexico. Much of this nitrate comes from agricultural production on seasonally wet soils where farmers have installed subsurface pipes or tiles to remove the excess water. Edge-offield practices have been developed to remove nitrate contained in these tiles before it enters streams and rivers. One of the newest practices, saturated riparian buffers can remove much of the nitrate that would otherwise leave a farmer's field. The practice removes nitrate primarily through a process called denitrification where organisms in the soil turn the nitrate into harmless nitrogen gas. However, a small amount of nitrous oxide gas can also be created during denitrification, which is a problem because nitrous oxide is a strong greenhouse gas. Thus, the removal of nitrate in saturated riparian buffers may be trading a water quality problem for an air quality problem. This research proves that saturated riparian buffers produce no more nitrous oxide gas than conventional buffers along streams and much less than if the ground were used for crop production. The impact of this finding is that action agencies are more likely to adopt and fund this practice for farmer use in the future.

Technical Abstract: Reestablishing perennial vegetation along riparian areas in agroecosystems reduces nutrient and sediment losses from agricultural runoff. However, subsurface (tile) drains route the majority of shallow groundwater through traditional buffers, limiting their nutrient removal capabilities. Saturated riparian buffers (SRBs) reconnect subsurface drainage water with the soil profile to remove nitrate in tile water through microbial denitrification. One concern of enhancing denitrification on agricultural landscapes is the increase in nitrous oxide (N2O) emissions from incomplete denitrification. Our study objective was to compare N2O emissions from SRBs to traditional buffers and bordering crop fields, at two sites, Bear Creek Site-1 (BC-1) and Iowa Site-1 (IA-1), in Central Iowa. We measured N2O emissions directly from the soil surface and dissolved in shallow groundwater, and estimated indirect emissions from downstream denitrification. Nitrous oxide emissions from soil surfaces were greatest from fertilized corn, and SRBs were only significantly greater (P < 0.05) than traditional buffers in one site-year. Dissolved N2O in shallow groundwater seeping from SRBs was not significantly greater (P < 0.05) than dissolved N2O from the tile outlet among site years. Indirect emissions from rivers and estuaries were significantly less at both sites. Overall, total N2O emissions from SRBs were similar to traditional buffers and less than fertilized corn-soybean agriculture.