Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: May 14, 2003
Publication Date: N/A
Nitrate in subsurface (tile) drainage from corn and soybean fields is an important source of contributing to excessive stream nitrate concentrations. Field and laboratory studies assessed the performance of wood chips as a carbon source for a denitrification wall. Drainage lines in the center of the plots led to equipment for measurement of flow and sampling. Wood was placed in trenches parallel to drain lines to intercept water and nitrate. Soybeans without N fertilizer were grown in 2001 and corn with N fertilizer was grown in 2002. Mean nitrate concentrations were reduced by the wood chip denitrification wall, but drainage volume was not affected, compared to the control plots. In 2001 the N loss was reduced from 70 kg N/ha to 20 kg N/ha by the denitrification wall. Laboratory experiments with **15N-NO3 showed that immobilization of N by microorganisms on the wood surface was not a significant N removal mechanism. After two years in the field, 11 to 34% of the wood was decomposed, with decomposition proceeding more slowly deeper in the soil. Wood chip and soil samples were treated with nitrate and acetylene to measure short-term denitrification rates. The microbial community on the wood chips had between 14 to 390 times greater denitrification activity than for the subsoils at similar depths.