Location: Agroecosystems Management ResearchTitle: A decade of saturated buffer research: results from long-term monitoring in Iowa
|JOHNSON, GABRIEL - Iowa State University|
|ISENHAT, THOMAS - Iowa State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2023
Publication Date: 8/6/2023
Citation: Johnson, G., Isenhat, T., Rogovska, N.P. 2023. A decade of saturated buffer research: results from long-term monitoring in Iowa [abstract]. SWCS International Annual Conference.
Technical Abstract: Saturated buffers are an edge-of-field practice designed to remove nitrate-nitrogen from subsurface drainage systems to improve downstream water quality. These practices function by routing a fraction of the nitrate-laden drainage into riparian buffer soils to enhance natural denitrification and plant uptake processes. Research of these practices began in 2011 in Iowa resulting in more than 40 site-years of data. This study reported herein combines published data (2011-2017) with additional monitoring data (2018-2022) to provide novel assessments of long-term performance across sites and years. Methods include monitoring drainage flow with pressure transducers and calibrated weirs, and approximate biweekly grab sampling of drainage and buffer groundwater for nitrate concentration. Total mass load reduction was assessed as the difference in nitrate concentration from stream-side wells (i.e., the “outlet” point) and the field drainage (i.e., the inlet point) multiplied by the total treated flow volume. Across 31 site-years, the total nitrogen load reduction averaged 45% (sd: 26%) and the reduction ranged from 19 to 81% averaged across the four sites. Mass load of nitrogen removed normalized for contributing drainage area averaged 4.52 to 14.17 kg/ha across four sites. Additional expected results include full data across 40 site-years, nitrate removal performance metrics normalized for saturated buffer length and inter-annual drainage variability, and assessment of temporal trends in performance. This study reinforces prevailing guidance that saturated buffers are highly effective at removing nitrogen from drainage waters and that optimal design and site selection are crucial to maximize nitrate mass removal. Future implementation efforts are recommended to prioritize high flow sites that can provide the highest cost efficiency ($/kg N) in water quality improvement.