EGU23-5615, updated on 10 Jan 2024
EGU General Assembly 2023
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Crop plant effects on denitrification – what have we learned in six years DASIM project?

Pauline Sophie Rummel1,2, Reinhard Well3, Johanna Pausch4, Paulina Englert1,5, Amanda Matson3, Lukas Beule6, Sebastian Floßmann4,7, Jonas Eckei1, Birgit Pfeiffer1,8, and Klaus Dittert1
Pauline Sophie Rummel et al.
  • 1Georg-August-Universität Göttingen, Plant Nutrition and Crop Physiology, Department of Crop Science, Göttingen, Germany (
  • 2University of Copenhagen, Department of Geosciences and Natural Resource Management, Geography, Copenhagen, Denmark
  • 3Thünen Institute of Climate-Smart Agriculture, Federal Research Institute for Rural Areas, Forestry and Fisheries, Braunschweig, Germany
  • 4Universtiy of Bayreuth, Agroecology, Faculty for Biology, Chemistry, and Earth Sciences, Bayreuth, Germany
  • 5Georg-August-Universität Göttingen, Agronomy, Department of Crop Science, Göttingen, Germany
  • 6Julius Kühn Institute (JKI) - Federal Research Centre for Cultivated Plants, Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Berlin, Germany
  • 7Karlsruhe Institute of Technology (KIT) Campus Alpin, Institute of Meteorology and Climate Research, Atmospheric Environmental Research, Division of Biogeochemical Processes, Garmisch-Partenkirschen, Germany
  • 8Georg-August-Universität Göttingen, Institute of Microbiology and Genetics, Department of Genomic and Applied Microbiology, Göttingen, Germany

Denitrification in agricultural crop production is one of the main sources of gaseous N2O and N2 losses to the environment. To successfully develop mitigation strategies, it is crucial to understand N2O production pathways, but also to quantify all other gaseous N losses, especially N2 emissions. Therefore, this project aimed (1) to identify the main drivers of denitrification during plant growth and in the post-harvest period, (2) to quantify denitrification derived N2O and N2 losses during the cropping season, and (3) to assess the interactions between plant litter quality, initial litter degradation, and formation of hotspots of N2O and N2 production. We conducted experiments on the laboratory, greenhouse, and field plot scale using the 15N gas flux method and HeO2 atmosphere to directly measure N2O and N2 losses and to determine the fraction of denitrification derived N losses. We worked with soils, crops, temperature and moisture conditions that are typical for our central German humid-temperate climate.

Plant growth affected all controlling factors of denitrification, especially soil moisture, NO3 and Corg availability. Crop species differed in their growing patterns and N uptake throughout the growing season controlling both N and C availability in soil. Accordingly, N2O and N2 emission patterns differed between crop species. Overall, emissions were highest when plant N uptake was low, i.e., during early growth stages and ripening, and after harvest. On the field scale, soil moisture and temperature were major controls of N2O+N2 losses.

In a climate chamber study under controlled temperature conditions, N2O and N2 fluxes mainly derived from denitrification of labeled 15NO3 in anoxic microsites, while nitrification simultaneously occurred in more oxic parts of the soil, potentially contributing to formation of unlabeled N2O. Increasing soil moisture with irrigation increased denitrification rates in anoxic hotspots, which corresponded with increasing N2O and especially N2 fluxes. At the same time, it restricted nitrification and thus decreased the share of nitrification-dependent processes contributing to N2O formation.

Incorporation of plant litter increased CO2, N2O, and N2 losses irrespective of litter quality, soil moisture or soil type/SOM content. We found that under O2 limiting conditions (70 % WFPS), the fraction of easily degradable C controlled the magnitude of N2O and N2 losses after litter incorporation. Under moderate soil moisture (50-60 % WFPS), interactions between litter degradation and SOM turnover affected the time course and processes contributing to N2O formation. Overall, our high-resolution gas flux measurements showed that N2O+N2 emissions from harvest residues can contribute significantly to the total N loss. 

How to cite: Rummel, P. S., Well, R., Pausch, J., Englert, P., Matson, A., Beule, L., Floßmann, S., Eckei, J., Pfeiffer, B., and Dittert, K.: Crop plant effects on denitrification – what have we learned in six years DASIM project?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5615,, 2023.