Effectiveness of saturated buffers on water pollutant reduction from agricultural drainage

Authors: JOHNSON, GABRIEL - Iowa State University; CHRISTIANSON, LAURA - University Of Illinois; CHRISTIANSON, REID - Minnesota Department Of Agriculture; DAVIS, MORGAN - University Of Missouri; DIAZ-GARCIA, CAROLINA - University Of Illinois; GROH, TYLER - Pennsylvania State University; ISENHART, THOMAS - Iowa State University; KJAERSGAARD, JEPPE - Minnesota Department Of Agriculture; Malone, Robert - Rob; PEASE, LINDSAY - University Of Minnesota; Rogovska, Natalia

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2023
Publication Date: 9/21/2023
Citation: Johnson, G., Christianson, L., Christianson, R., Davis, M., Diaz-Garcia, C., Groh, T., Isenhart, T., Kjaersgaard, J., Malone, R.W., Pease, L., Rogovska, N.P. 2023. Effectiveness of saturated buffers on water pollutant reduction from agricultural drainage. Journal of the ASABE. 1(1): 49-62. https://doi.org/10.13031/jnrae.15516.
DOI: https://doi.org/10.13031/jnrae.15516

Interpretive Summary: Agricultural soils of the Upper Midwest are highly productive; however, poor drainage can contribute to prolonged waterlogged conditions that negatively impact crop production. While artificial subsurface drainage via field tiles (pipes) improves waterlogged soils, tile drainage discharge to surface waters is a major source of nitrogen losses, especially nitrate. A novel approach for reducing nitrate loss is to intercept a field tile where it crosses the land adjacent to a ditch, stream, or river – known as a riparian buffer – and divert a fraction of the flow to shallow groundwater within the buffer. This practice is called a saturated buffer. The objective of this review was to summarize the state of the science for saturated buffers in the US with emphasis on performance and cost. Saturated buffers removed roughly 50% of the nitrogen load which would have otherwise gone downstream. This research will be of interest to producers and policy makers as a promising drainage conservation practice aimed at improving water quality.

Technical Abstract: It is a pivotal time in the development of saturated buffers as a conservation drainage practice. Field data have demonstrated this practice can be effective for reducing nitrate loads in subsurface drainage. Compilation and assessment of current knowledge for this relatively new practice is timely to help identify future opportunities. The objective of this review was to summarize the state of the science for saturated buffers in the US within the context of this special collection’s emphasis on performance and cost. Suggested research areas were also identified to improve understanding of saturated buffer functioning and performance and to refine design processes and criteria to accelerate their adoption. As currently designed, saturated buffers removed an average of 46 ± 24% (mean ± sd) of the nitrogen (N) load which would have otherwise gone downstream (9.4 ± 5.9 kg N removed/ha-y; n = 30 site-years). Cost efficiencies, which generally trended around $3 to $5/kg N removed per year, were considered relatively efficient (range: $1.20 to $9.20/kg N/y). As adoption is scaled, engineering design costs need to be considered unless the design model can be simplified. Recommended future research includes refining design processes, management, and siting criteria to facilitate scaled adoption for water quality goals. Additional studies on nutrient cycling within saturated buffers are needed to fill gaps about nitrogen and phosphorus dynamics and about the importance of the buffer’s vegetation. Saturated buffers are a conservation drainage practice with much potential for tile-drained landscapes. The time is right to continue to advance this practice through additional knowledge generation.