Nitrate-Nitrogen Export: Magnitude and Patterns from Drainage Districts to Downstream River Basins

Abstract

Alteration of the prairie pothole ecosystem through installation of subsurface tile drains has enabled the U.S. Corn Belt to become one of the most agriculturally productive areas in the world but has also led to increased nitrogen losses to surface water. The literature contains numerous field plot studies but few in-depth studies of nitrate exports from small, tile-drained catchments representative of agricultural drainage districts. The objectives of this study were to quantify hydrology and nitrate-nitrogen (NO-N) export patterns from three tile-drained catchments and the downstream river over a 5-yr period, compare results to prior plot-, field-, and watershed-scale studies, and discuss implications for water quality improvement in these landscapes. The tile-drained catchments had an annual average water yield of 247 mm yr, a flow-weighted NO-N concentration of 17.1 mg L, and an average NO-N loss of nearly 40 kg ha yr. Overall, water yields were consistent with prior tile drainage studies in Iowa and the upper Midwest, but associated NO-N concentrations and losses were among the highest reported for plot studies and higher than those found in small watersheds. More than 97% of the nitrate export occurs during the highest 50% of flows, at both the small catchment and river basin scale. Findings solidified the importance of working at the drainage district scale to achieve nitrate reductions necessary to meet water quality goals. They also point to the need for implementing strategies that address both hydrology and nitrogen supply in tile-drained landscapes.

Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges

“…The BER operating costs were for electricity, which were based on scaling power per unit volume from the small to full-scale reactors, and on electricity rates assumed at $0.08/kWh. However, the BER was expected to operate with electrical stimulation under high-flow conditions only, which was assumed to be 10% annually (Ikenberry et al, 2014). The maintenance costs were for anode replacement, which were based upon anode degradation rates observed in the experimental reactors.…”

“…In this analysis, the nitrate removal efficiency of the full-scale BERs was expected to be equal to the results in our laboratory experiment. We also assumed treatment area of 22.2 ha with nitrate export rate at 31.4 kg NO 3 -N/ha-yr (Christianson et al, 2013;Ikenberry et al, 2014). We assumed 56% of the nitrate is exported during 10% of daily flow, and this drainage water was treated with electrical stimulation; the remaining 44% would be treated without electrical stimulation (Ikenberry et al, 2014).…”

“…We also assumed treatment area of 22.2 ha with nitrate export rate at 31.4 kg NO 3 -N/ha-yr (Christianson et al, 2013;Ikenberry et al, 2014). We assumed 56% of the nitrate is exported during 10% of daily flow, and this drainage water was treated with electrical stimulation; the remaining 44% would be treated without electrical stimulation (Ikenberry et al, 2014). The nitrate removal efficiency (18.5%) of traditional treatment was assumed to be the same as our control reactors.…”

“…While hypoxia is the most common problem, excessive nutrients in aquatic ecosystems also may result in acidification of these aquatic systems (Camargo and Alonso, 2006). In addition, nitrate poses risks to human and animal health when occurring in drinking water at concentrations exceeding 10 mg/L as N (Camargo and Alonso, 2006;USEPA, 2009), and such concentrations are regularly found in tile drainage of high-production agricultural landscapes (Hofmann et al, 2004;Ikenberry et al, 2014;Kalita et al, 2007;Lawlor et al, 2008).…”

Temperature and Substrate Control Woodchip Bioreactor Performance in Reducing Tile Nitrate Loads in East-Central Illinois

“…The effectiveness of these practices is variable from location to location and temporally due to differing tile flow amounts and nitrate concentrations. Edgeof-field techniques have particular difficulty reducing nitrate loads during high-flow periods, when most transport occurs (Royer et al, 2006;Ikenberry et al, 2014;Moorman et al, 2015).Wood chip bioreactors have been installed at the end of tile lines from many fields in the Midwest. A wide range of nitrate removal effectiveness (up to 98% nitrate reductions) in laboratory and field studies has been reported in the literature (Greenan et al, 2009;Chun et al, 2009Chun et al, , 2010Moorman et al, 2010;Verma et al, 2010;Woli et al, 2010;Christianson et al, 2012b;Bell et al, 2015).…”