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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 #354218
Research Project: Agroecosystem Benefits from the Development and Application of New Management Technologies in Agricultural Watersheds

Location: Agroecosystems Management Research

Title: In situ denitrification in saturated riparian buffers

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

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 11/8/2018
Citation: Groh, T.A., Davis, M.P., Isenhart, T.M., Jaynes, D.B., Parkin, T.B. 2018. In situ denitrification in saturated riparian buffers. Journal of Environmental Quality. 48(2):376-384. https://doi.org/10.2134/jeq2018.03.0125.
DOI: https://doi.org/10.2134/jeq2018.03.0125

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. This research proves that much of the nitrate that is removed is removed through a process called denitrification where organisms in the soil turn the nitrate into harmless nitrogen gas rather than merely re-cycling the nitrogen. 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: Excess nitrate leaching from the agricultural Midwest via tile drainage water has caused both local drinking water and national Gulf of Mexico benthic hypoxia problems. Both in-field and edge-of-field practices have been designed to help mitigate a portion of the nitrate leaching. These practices focus on maximizing microbial denitrification, the conversion of nitrate to dinitrogen gas. This study specifically focuses on the denitrification rates obtained from diverting nitrate-rich tile drainage water into riparian buffers’ soils, thus creating a saturated riparian buffer, SRB. The SRBs in this study removed between 27 and 96.4% of the total diverted nitrate load. The cumulative average denitrification rate for each SRB sample year accounted for between 3.7 and 77.3% of the total amount of nitrate removed by the SRBs. Both the cumulative maximum and 90% confidence interval denitrification rates accounted for all of the nitrate removed by the SRBs in three out of the five sample years, indicating that denitrification can be a dominant nitrate removal mechanism in this edge-of-field practice. Buffer age, defined as time since establishment, seemed to correlate with higher denitrification rates, and there was also a trend of the soil closer to the surface making up the majority of each denitrification rate. Further, both nitrate and carbon could be limiting factors for denitrification in these SRBs, and need to be looked at in more detail.