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Nitrate‐Nitrogen Export: Magnitude and Patterns from Drainage Districts to Downstream River Basins
Author(s) -
Ikenberry Charles D.,
Soupir Michelle L.,
Schilling Keith E.,
Jones Christopher S.,
Seeman Anthony
Publication year - 2014
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2014.05.0242
Subject(s) - tile drainage , hydrology (agriculture) , environmental science , watershed , nitrate , drainage basin , water quality , drainage , surface water , soil water , environmental engineering , geography , ecology , geology , soil science , geotechnical engineering , cartography , machine learning , biology , computer science
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 3 –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 −1 , a flow‐weighted NO 3 –N concentration of 17.1 mg L −1 , and an average NO 3 –N loss of nearly 40 kg ha −1 yr −1 . Overall, water yields were consistent with prior tile drainage studies in Iowa and the upper Midwest, but associated NO 3 –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.