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Nutrient retention in tile‐fed and non‐tile reconstructed oxbows in north central Iowa
Journal article   Open access   Peer reviewed

Nutrient retention in tile‐fed and non‐tile reconstructed oxbows in north central Iowa

Sophie Pierce and Keith E. Schilling
Journal of the American Water Resources Association, Vol.59(5), pp.913-928
10/2023
DOI: 10.1111/1752-1688.13124
Appears in  UI Libraries Support Open Access
url
https://doi.org/10.1111/1752-1688.13124View
Published (Version of record) Open Access

Abstract

Nutrient export from the agricultural Midwest threatens the Gulf of Mexico and new conservation practices are needed to reduce the loss of nutrient from subsurface tile drainage systems. Oxbows are natural waterbodies formed when a river cuts off a meander loop and water quality benefits of reconstructed oxbows are being increasingly recognized. In this study, we monitored four reconstructed oxbow sites (two tile-fed, two non-tile) over a 2-year period in north-central Iowa and assessed their capacity for NO3-N and dissolved reactive phosphorus (DRP) reductions. Water flow and quality monitoring of tiles, shallow groundwater, oxbow and receiving streams documented that the oxbows were dominated by tile drainage inputs. NO3-N concentrations were highest in the drainage tiles flowing into the tile-fed oxbows (mean 8–10 mg/L) and much lower in floodplain groundwater (<1–2 mg/L). Annual NO3-N loads into the tile-fed oxbows were substantially larger than input loads into the non-tiled oxbows. For the two tile-fed oxbows, the 2-year NO3-N retention efficiencies were very similar (0.76–0.77) and on a monthly basis, greater retention efficiencies were measured in summer and fall. DRP concentrations and loads into the tile-fed oxbows were too low to allow for meaningful estimates of retention. Reconstructing oxbows to receive tile drainage water should be considered a sustainable conservation practice for tile drainage treatment in agricultural areas.
 oxbow nitrate dissolved reactive phosphorus tile drainage nature-based solutions conservation practices UIOWA OA Agreement

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