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Title: Denitirification and N2O emission in arable soils: Effect of tillage, N source and soil moisture.

Author
item LIU, XUEJUN - CH AG UNIV, BEIJING, CH
item MOSIER, A - USDA-ARS RETIRED
item Halvorson, Ardell
item Reule, Curtis
item ZHANG, FUSUO - CH AG UNIV, BEIJING, CH

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2007
Publication Date: 5/15/2007
Citation: Liu, X.J., Mosier, A.R., Halvorson, A.D., Reule, C.A., Zhang, F. 2007. Denitirification and N2O emission in arable soils: Effect of tillage, N source and soil moisture. Journal of Soil Biology and Biochemistry. 39:2362-2370.

Interpretive Summary: Little is known about how tillage, N source and moisture status control soil respiration, nitrous oxide and denitrification. A laboratory investigation was performed to quantify the interaction of carbon dioxide (CO2), nitrous oxide (N2O) and dinitrogen (N2)+N2O (representing denitrification) fluxes in no-till (NT) and conventional till (CT) soils. Soil cores were incubated at 25 oC at 75% and 60% water filled pore space (WFPS) with addition of 15N labeled NH4 and NO3 fertilizers (100 mg N kg-1 soil). Higher accumulative CO2, N2O and N2+N2O fluxes were observed in NT soil than in CT soil irrespective of N source and soil moisture content. Compared to soil emission, fertilizer N contributed more than 80% of total N2O and N2+N2O emissions. Such contributions, on average, were greater in NT (89%) than in CT (80%), which suggests greater denitrification potential in NT soil. The addition of NH4 fertilizer generally led to higher CO2, N2O and N2+N2O fluxes from both NT and CT soils, particularly at lower soil moisture content (60% WFPS). Both fertilizer and soil derived N2O and N2+N2O emissions from 15NH4-treated soil were higher than those from 15NO3-treated soil at 60% WFPS, indicating that the increase in N2O emission induced by NH4 fertilizer addition is owed to both nitrification and nitrification-induced denitrification. Higher soil moisture content (75% WFPS) enhanced total N2O and N2+N2O fluxes, while CO2 efflux was not affected by soil moisture content. Significant interactions of N2O and N2+N2O fluxes between tillage and N source or soil moisture content were present.

Technical Abstract: There is a lack of understanding of how tillage, N source and moisture status control soil respiration, nitrous oxide and denitrification. A laboratory investigation was performed to quantify the interaction of carbon dioxide (CO2), nitrous oxide (N2O) and dinitrogen (N2)+N2O (representing denitrification) fluxes in no-till (NT) and conventional till (CT) soils. Intact soil cores (0-10 cm) were incubated at 25 oC at 75% and 60% water filled pore space (WFPS) with addition of 15N labeled ammonium and nitrate fertilizers (100 mg N kg-1 soil). We observed significantly higher accumulative CO2, N2O and N2+N2O fluxes in NT soil than in CT soil irrespective of N source and soil moisture content. Compared to N derived from soil, fertilizer N contributed more than 80% of total N2O and N2+N2O emissions. Such contributions, on average, were greater in NT (89%) than in CT (80%), which suggests greater denitrification potential in NT soil. The addition of ammonium fertilizer generally led to higher CO2, N2O and N2+N2O fluxes from both NT and CT soils, particularly at lower soil moisture content (60% WFPS). Both fertilizer and soil derived N2O and N2+N2O emissions from 15NH4-treated soil were higher than those from 15NO3-treated soil at 60% WFPS, indicating that the increase in N2O emission induced by ammonium fertilizer addition is owed to both nitrification and nitrification-induced denitrification. Higher soil moisture content (75% WFPS) enhanced total N2O and N2+N2O fluxes, while CO2 efflux was not affected by soil moisture content. There were significant interactions of N2O and N2+N2O fluxes between tillage and N source or soil moisture content.