Irrigation and Drainage
394460 - Impact of drying-rewetting cycles on gaseous and aqueous C/N cycling in denitrification beds
Wednesday, June 6
4:00 PM - 5:30 PM
Location: Skyway Room
Francois Birgand, Associate Professor – NCSU; Laura Christianson, Illinois – University of Illinois; Louis Schipper, Waikato, NZ – University of Waikato; David Williams, North Carolina – EPA; Huaihai Chen, North Carolina – EPA; Mohamed Youssef, North Carolina – North Carolina State University; George Chescheir, North Carolina – North Carolina State University; Matt Helmers, Iowa – Iowa State University
Engineered, carbon-rich substrate agricultural BMPs (e.g., wetlands and woodchips bioreactors) are widely used to control N export from animal farms and crop fields by promoting denitrification. There is abundant evidence that drying-rewetting (DRW) events can promote enhanced metabolic rates in soils. Control of the water table within BMPs, possible through hydraulic management, can be used to create DRW cycles. A 12-month experiment was conducted at NC State University to quantify the effects of periodic DRW cycles on nitrate removal efficiency in woodchip columns receiving nitrated water at constant flow. Eight columns were either exposed to prolonged saturation (SAT) or to weekly 8-hr DRW cycles (DRW). Aqueous concentrations of select C and N forms were measured at the column outlets every two hours using multiplexed sampling methods and spectrophotometric analysis. Gaseous concentrations of select C and N forms in the headspace above the columns were also measured along with isotopes of N2O. DRW columns showed immediate response to drying periods, with greater export of DOC and TC. DRW columns also showed immediate increase in NO3 removal rates. After 8 months DRW columns show a sustained 10-20% greater NO3 removal, relative to SAT columns. This presentation will cover aqueous and gaseous exports from the columns, as well as presentation of results from microbial community composition analysis. The research has broad applications for management of carbonaceous systems for denitrification.