Volume 32, Issue 13 p. 1053-1067
RESEARCH ARTICLE

Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules

Caroline Buchen

Corresponding Author

Caroline Buchen

Thünen-Institute of Climate-Smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany

Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Muencheberg, Germany

Correspondence

C. Buchen, Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Str. 84, 15374 Muencheberg, Germany.

Email: [email protected]

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Dominika Lewicka-Szczebak

Dominika Lewicka-Szczebak

Thünen-Institute of Climate-Smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany

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Heinz Flessa

Heinz Flessa

Thünen-Institute of Climate-Smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany

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Reinhard Well

Reinhard Well

Thünen-Institute of Climate-Smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany

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First published: 30 March 2018
Citations: 42

Abstract

Rationale

Enhanced nitrous oxide (N2O) emissions can occur following grassland break-up for renewal or conversion to maize cropping, but knowledge about N2O production pathways and N2O reduction to N2 is very limited. A promising tool to address this is the combination of mass spectrometric analysis of N2O isotopocules and an enhanced approach for data interpretation.

Methods

The isotopocule mapping approach was applied to field data using a δ15NspN2O and δ18ON2O map to simultaneously determine N2O production pathways contribution and N2O reduction for the first time. Based on the isotopic composition of N2O produced and literature values for specific N2O pathways, it was possible to distinguish: (i) heterotrophic bacterial denitrification and/or nitrifier denitrification and (ii) nitrification and/or fungal denitrification and the contribution of N2O reduction.

Results

The isotopic composition of soil-emitted N2O largely resembled the known end-member values for bacterial denitrification. The isotopocule mapping approach indicated different effects of N2O reduction on the isotopic composition of soil-emitted N2O for the two soils under study. Differing N2O production pathways in different seasons were not observed, but management events and soil conditions had a significant impact on pathway contribution and N2O reduction. N2O reduction data were compared with a parallel 15N-labelling experiment.

Conclusions

The field application of the isotopocule mapping approach opens up new prospects for studying N2O production and consumption of N2O in soil simultaneously based on mass spectrometric analysis of natural abundance N2O. However, further studies are needed in order to properly validate the isotopocule mapping approach.