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Denitrification in the shallow ground water of a tile-drained, agricultural watershed

Journal of Environmental Quality

By:
, , , , ,
DOI: 10.2134/jeq2006.0096

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Abstract

Nonpoint-source pollution of surface water by N is considered a major cause of hypoxia. Because Corn Belt watersheds have been identified as major sources of N in the Mississippi River basin, the fate and transport of N from midwestern agricultural watersheds have received considerable interest. The fate and transport of N in the shallow ground water of these watersheds still needs additional research. Our purpose was to estimate denitrification in the shallow ground water of a tile-drained, Corn Belt watershed with fine-grained soils. Over a 3-yr period, N was monitored in the surface and ground water of an agricultural watershed in central Illinois. A significant amount of N was transported past the tile drains and into shallow ground water. The ground water nitrate was isotopically heavier than tile drain nitrate, which can be explained by denitrification in the subsurface. Denitrifying bacteria were found at depths to 10 m throughout the watershed. Laboratory and push-pull tests showed that a significant fraction of nitrate could be denitrified rapidly. We estimated that the N denitrified in shallow ground water was equivalent to 0.3 to 6.4% of the applied N or 9 to 27% of N exported via surface water. These estimates varied by water year and peaked in a year of normal precipitation after 2 yr of below average precipitation. Three years of monitoring data indicate that shallow ground water in watersheds with fine-grained soils may be a significant N sink compared with N exported via surface water. ?? ASA, CSSA, SSSA.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Denitrification in the shallow ground water of a tile-drained, agricultural watershed
Series title:
Journal of Environmental Quality
DOI:
10.2134/jeq2006.0096
Volume
36
Issue:
1
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Environmental Quality
First page:
80
Last page:
90
Number of Pages:
11