Abstract of Conference poster presentatio

Coxon, Catherine E.

Jahangir, Mohammad M. R.

Johnston, Paul

Minet, E.

Richards, Karl G.

English

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Geophysical Research AbstractsVol. 16, EGU2014-3952-1, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.In situ denitrification rates in shallow groundwater beneath a springbarley - mustard cover crop systemMohammad Mofizur Rahman Jahangir (1,2), Eddy Minet (2), Paul Johnston (1), Catherine Coxon (3), and KarlRichards (2)(1) Univerity of Dublin-Trinity College, Department of Civil, Structural & Environmental Engineering, Dublin, Ireland(jahangim@tcd.ie), (2) Teagasc Environment Research Centre, (3) University of Dublin-Trinity College, School of NaturalScienceMustard catch crop has been reported to increase dissolved organic carbon (DOC) concentrations in groundwater,which can be used as an energy source for denitrifiers. This study investigates the impact of a mustard catch cropon in situ denitrification and nitrous oxide (N2O) emissions from an aquifer overlain by arable land. Denitrifica-tion rates and N2O-N/(N2O-N+N2-N) mole fractions were measured in situ with a push-pull method in shallowgroundwater under a spring barley system in experimental plots with an without a mustard cover crop. The resultssuggest that a mustard cover crop could substantially enhance reduction of groundwater nitrate (NO3–N) via den-itrification without significantly increasing N2O emissions. Mean total denitrification (TDN) rates below mustardcover crop and no cover crop were 7.61 and 0.002 µg kg-1 d-1, respectively. Estimated N2O-N/(N2O-N+N2-N)ratios, being 0.001 and 1.0 below mustard cover crop and no cover crop respectively, indicate that denitrificationbelow mustard cover crop reduces N2O to N2, unlike the plot with no cover crop. The observed enhanced deni-trification under the mustard cover crop may result from the higher groundwater DOC under mustard cover crop(1.53 mg L-1) than no cover crop (0.90 mg L-1) being added by the root exudates and root masses of mustard.This study gives insights into the missing piece in agricultural nitrogen (N) balance and groundwater derived N2Oemissions under arable land.

In situ denitrification rates in shallow groundwater beneath a springbarley - mustard cover crop system

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