Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 10, 2002
Publication Date: November 14, 2002
Citation: MOORMAN, T.B., DOUGLASS, E.A. EFFECT OF DISSOLVED ORGANIC CARBON AND PHENOLIC ACIDS ON DENTRIFICATION IN SUBSURFACE SOIL. AMERICAN SOCIETY OF AGRONOMY MEETINGS. 2002. CD-ROM. MADISON, WI.
Nitrate removal from groundwater has been attributed to dentrification, but the carbon sources driving microbial metabolism in subsurface soils have not been investigated. Dissolved organic carbon (DOC) leaching from the root zone to deeper sediments is a likely source for C for metabolism. Saturated subsoils (9.4 to 10 m depth) were amended with 50 mg of 15N03 per kg soil and treated with DOC extracted from shallow subsoil (1 to 2 m depth) or (ring-14C) ferulic, coumaric or benzoic acid, then incubated under anaerobic conditions. DOC addition caused significant reduction in nitrate compared to controls in two sediments. DOC half-lives ranged from 6 to 14 days. Nitrate concentrations remained constant in subsoils without added C substrates. Incorporation of 15N into microbial biomass or other organic forms accounted for 17 to 88% of the nitrate removal. Production of 14CO2 was least for ferulic acid and greatest for benzoic acid. DOC from soil can effectively support dentrification in subsoils below the root zone. Mineralization of benzoic and coumaric acids demonstrate that the microbial community can degrade aromatic components of DOC under dentrifying conditions.