EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Which N2O production processes are relevant when converting from grassland to cropland?

Caroline Buchen-Tschiskale1, Dominika Lewicka-Szczebak2, Greta Nicolay1, Mirjam Helfrich1, Heinz Flessa1, and Reinhard Well1
Caroline Buchen-Tschiskale et al.
  • 1Thuenen-Institute of Climate-Smart Agriculture, Braunschweig, Germany
  • 2University of Wrocław, Wrocław, Poland

During the last decades, large areas of grassland were converted to cropland across Europe, mainly due to the increasing demand of cropland following the expansion of biogas plant production (e.g. maize). However, the conversion to cropland bears a risk of nitrous oxide (N2O) emission due to enhanced nitrogen (N) mineralization. Until now, knowledge about N2O production pathways due to grassland conversion and in particular N2O reduction to N2 is very limited (Buchen et al., 2018), even though understanding of N2O processes and identification of sources are needed in order to devise mitigation options.

N2O samples were collected periodically from manual chambers following chemical and mechanical conversion from permanent grassland to cropland (maize) at two sites with different texture (clayey loam and sandy loam) and fertilization regime (with and without mineral N-fertilization) in north-western Germany (Helfrich et al., 2020). Samples were analysed for natural abundance stable isotope signatures of soil-emitted N2O (δ15NbulkN2O, δ18ON2O and δ15NSPN2O = intramolecular distribution of 15N in the N2O molecule) by isotope ratio mass spectrometry (IRMS) and dual-isotope of N2O isotopic signatures (plotting δ15NSPN2O vs. δ18ON2O) were used for data evaluation (Lewicka-Szczebak et al., 2017). Although, isotopic signatures were very variable throughout the year at both sites, the clayey loam site exhibited a close correlation between δ15NspN2O and δ18ON2O suggesting that values were mainly controlled by N2O reduction to N2. At the sandy loam site this pattern was less pronounced, possibly because processes other than bacterial denitrification (e.g. fungal denitrification and nitrification) also significantly influence isotopocule values. Altogether, bacterial denitrification was found to be the most important process following grassland conversion to maize cropping.


Buchen, C., Lewicka‐Szczebak, D., Flessa, H., Well, R., 2018. Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules. Rapid Communications in Mass Spectrometry 32, 1053-1067.

Helfrich, M., Nicolay, G., Well, R., Buchen-Tschiskale, C., Dechow, R., Fuß, R., Gensior, A., Paulsen, H., Berendonk, C., Flessa, H., 2020. Effect of chemical and mechanical grassland conversion to cropland on soil mineral N dynamics and N2O emission. Agriculture, Ecosystems & Environment 298, 106975.

Lewicka-Szczebak, D., Augustin, J., Giesemann, A., Well, R., 2017. Quantifying N2O reduction to N2 based on N2O isotopocules – validation with independent methods (helium incubation and 15N gas flux method). Biogeosciences 14, 711-732.

How to cite: Buchen-Tschiskale, C., Lewicka-Szczebak, D., Nicolay, G., Helfrich, M., Flessa, H., and Well, R.: Which N2O production processes are relevant when converting from grassland to cropland?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2623,, 2023.