Groundwater nutrient concentrations during prairie reconstruction on an Iowa landscape
Dates
Year
2009
Citation
Tomer, M. D., Schilling, K. E., Cambardella, C. A., Jacobson, P., and Drobney, P., 2009, Groundwater nutrient concentrations during prairie reconstruction on an Iowa landscape: Agriculture, Ecosystems & Environment, v. 139, no. 1–2, p. 206-213.
Summary
One anticipated benefit of ecosystem restoration is water quality improvement. This study evaluated NO3-N and phosphorus in subsurface waters during prairie establishment following decades of row-crop agriculture. A prairie seeding in late 2003 became established in 2006. Wells and suction cup samplers were monitored for NO3-N and phosphorus. Nitrate-N varied with time and landscape position. Non-detectable NO3-N concentrations became modal along ephemeral drainageways in 2006, when average concentrations in uplands first became <10 mg NO3-N L−1. This decline continued and upland groundwater averaged near 2 mg NO3-N L−1 after 2007. The longer time lag in NO3-N response in uplands was attributed to greater quantities of leachable N [...]
Summary
One anticipated benefit of ecosystem restoration is water quality improvement. This study evaluated NO3-N and phosphorus in subsurface waters during prairie establishment following decades of row-crop agriculture. A prairie seeding in late 2003 became established in 2006. Wells and suction cup samplers were monitored for NO3-N and phosphorus. Nitrate-N varied with time and landscape position. Non-detectable NO3-N concentrations became modal along ephemeral drainageways in 2006, when average concentrations in uplands first became <10 mg NO3-N L−1. This decline continued and upland groundwater averaged near 2 mg NO3-N L−1 after 2007. The longer time lag in NO3-N response in uplands was attributed to greater quantities of leachable N in upland subsoils. Spatial differences in vadose-zone travel times were less important, considering water table dynamics. Phosphorus showed a contrasting landscape pattern, without any obvious temporal trend. Phosphorus was greatest along and near ephemeral drainageways. Sediment accumulation from upland agricultural erosion provided a source of P along drainageways, where shallow, reductive groundwater increased P solubility. Phosphorus exceeded eutrophication risk thresholds in these lower areas, where saturation-excess runoff could readily transport P to surface waters. Legacy impacts of past agricultural erosion and sedimentation may include soluble phosphorus in shallow groundwater, at sites prone to saturation-excess runoff.