Teagasc Environment Research Center, Johnstown Castle, Wexford, Ireland; Dept. of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland; Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh.
Teagasc Environment Research Center, Johnstown Castle, Wexford, Ireland.
Chemosphere. 2014 May;103:234-9. doi: 10.1016/j.chemosphere.2013.11.072. Epub 2013 Dec 26.
Over-winter green cover crops have 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 crop on in situ denitrification and nitrous oxide (N2O) emissions from an aquifer overlain by arable land. Denitrification rates and N2O-N/(N2O-N+N2-N) mole fractions were measured in situ with a push-pull method in shallow groundwater under a spring barley system in experimental plots with and without a mustard cover crop. The results suggest that a mustard cover crop could substantially enhance reduction of groundwater nitrate NO3--N via denitrification without significantly increasing N2O emissions. Mean total denitrification (TDN) rates below mustard cover 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 denitrification below mustard cover crop reduces N2O to N2, unlike the plot with no cover crop. The observed enhanced denitrification 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 N2O emissions under arable land and thus helps minimise the uncertainty in agricultural N and N2O-N balances.
越冬绿肥作物已被报道会增加地下水的溶解有机碳 (DOC) 浓度，而 DOC 可以作为反硝化菌的能源。本研究调查了芥菜覆盖作物对耕地覆盖含水层中原位反硝化和氧化亚氮 (N2O) 排放的影响。在实验田的春大麦系统中，使用推-拉法原位测量了有和没有芥菜覆盖作物的浅层地下水中的反硝化速率和 N2O-N/(N2O-N+N2-N)摩尔分数。结果表明，芥菜覆盖作物可以在不显著增加 N2O 排放的情况下，大量增强地下水硝酸盐 NO3--N 的还原作用。芥菜覆盖作物下和无覆盖作物下的平均总反硝化 (TDN) 速率分别为 7.61 和 0.002μgkg(-1)d(-1)。估计的 N2O-N/(N2O-N+N2-N)比值分别为芥菜覆盖作物下和无覆盖作物下的 0.001 和 1.0，表明芥菜覆盖作物下的反硝化将 N2O 还原为 N2，而无覆盖作物下则不然。芥菜覆盖作物下观察到的增强反硝化作用可能是由于芥菜覆盖作物下的地下水中有更多的 DOC（1.53mgL(-1)），而无覆盖作物下只有 0.90mgL(-1)，这是芥菜的根分泌物和根团添加的。本研究深入了解了耕地和地下水衍生的 N2O 排放中农业氮 (N) 平衡的缺失部分，从而有助于减少农业 N 和 N2O-N 平衡的不确定性。
