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United States Department of Agriculture

Agricultural Research Service

Title: COMPARING CARBON SUBSTRATES FOR DENITRIFICATION OF SUBSURFACE DRAINAGE WATER

Authors
item Greenan, Colin
item MOORMAN, THOMAS
item KASPAR, THOMAS
item PARKIN, TIMOTHY
item JAYNES, DAN

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 19, 2005
Publication Date: April 3, 2006
Citation: Greenan, C.M., Moorman, T.B., Kaspar, T.C., Parkin, T.B., Jaynes, D.B. 2006. Comparing carbon substrates for denitrification of subsurface drainage water. Journal of Environmental Quality. 35:824-829.

Interpretive Summary: Nitrate in water from tile drained corn and soybean fields in the Midwest contributes to nitrate contamination of surface waters. Denitrification is the the process whereby soil microorganisms convert nitrate to dinitrogen gas (N2). Denitrification-based biofilters are a promising strategy for reducing nitrate concentrations, but these systems require an external carbon supply to sustain denitrification. The ability of four organic materials to serve as carbon substrates to support microbial denitrification biofilters. Wood chips, wood chips amended with soybean oil, cornstalks, and cardboard fibers stimulated NO3-N removal and the degree of removal from highest to lowest was: cornstalks, cardboard fibers, wood chips with oil, and wood chips alone. Using an isotope tracer,15N, we showed that immobilization and nitrate reduction to ammonium accounted for <4% of nitrate removal in all treatments, therefore denitrification was the dominant nitrate removal process. This work supported our field work by showing that denitrification was the dominant loss mechanism. This work and the field studiec show that these types of biofilters can be used to remove nitrate leaving farmers fields. The research will be used by NRCS, farm groups and producers interested in this novel technology for nitrate removal from drainage water.

Technical Abstract: Nitrate in water from tile drained corn and soybean fields in the Midwest contributes to nitrate contamination of surface waters. Denitrification-based biofilters are a promising strategy for reducing nitrate concentrations, but these systems require an external carbon supply to sustain denitrification. The ability of four organic materials to serve as carbon substrates for denitrification biofilters was evaluated in this laboratory study. Wood chips, wood chips amended with soybean oil, cornstalks, and cardboard fibers were mixed with subsoil (oxidized till) and incubated anaerobically for 180 days. 15NO3-N was added periodically to maintain nitrate-N concentrations between 10 and 100 mg L-1. All of the materials stimulated NO3-N removal and the degree of removal from highest to lowest was: cornstalks, cardboard fibers, wood chips with oil, and wood chips alone. Analysis of 15N showed that immobilization and dissimilatory nitrate reduction to ammonium accounted for <4% of NO3-N removal in all treatments, therefore denitrification was the dominant NO3-N removal process. Cardboard fibers, wood chips and oil, and wood chips alone did not support as much denitrification as cornstalks, but their rates of NO3-N removal were steady and would probably continue longer than cornstalks. Grinding wood chips and cardboard fibers enhanced denitrification, and addition of soybean oil to wood chips significantly increased denitrification rates in early phases of the incubation.

Last Modified: 8/27/2014
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