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Critical soil organic carbon levels in arable soils

PhD defence, Friday 27 March 2020. Johannes L. Jensen.

2020.03.27 | Sunitha Satkunam

Johannes Lund Jensen

During his studies, Johannes L. Jensen researched the critical level of soil organic carbon at which essential soil functions are compromised. Soil organic carbon is important for soil properties and functions. Accordingly, loss of carbon is considered a main threat to sustained soil functions. The main hypothesis was that the ratio of soil clay to carbon constitutes a better basis than the carbon content per se for identifying a critical threshold for soil functions. In addition, Johannes L. Jensen investigated how short-term changes in soil management affected the carbon content and soil functions. The results showed that the content of carbon was not a good predictor of proper soil functioning across different soil types. Instead, the ratio of soil clay to carbon was a better indicator for soil physical condition. Short-term changes in soil tillage and organic matter input affected soil physical properties. The changes in soil physical properties could not solely be ascribed to changes in carbon content, but also to changes in soil management.

The new research findings provide an improved basis for identification of critical levels of soil organic carbon, including the possibilities and limitations associated with the use of critical threshold values. 

The PhD degree was completed at the Department of Agroecology, Faculty of Technical Sciences, Aarhus University.

This résumé was prepared by the PhD student.

Time: Friday 27 March 2020 at 10.00
Place:  Will be held online    
Title of PhD thesis: Identification of soil organic carbon thresholds for sustaining soil functions in arable mineral soils from the humid temperature region
Contact information: Johannes L. Jensen, e-mail: jlj@agro.au.dk, tel.: +45 26360847
Members of the assessment committee:
Research Scientist Dr, Edward G. Gregorich, Ottawa Research and Development Centre, Agriculture and Agri-Food, Canada
Professor Paul Hallett, The School of Biological Sciences, University of Aberdeen, Scotland
Senior Researcher Chris Kjeldsen (chair), Department of Agroecology, Aarhus University
Main supervisor:
Professor Lars J. Munkholm, Department of Agroecology, Aarhus University
Senior Researcher Per Schjønning, Department of Agroecology, Aarhus University
Professor Bent T. Christensen, Department of Agroecology, Aarhus University
Researcher Christopher W. Watts, Department of Sustainable Agriculture Sciences, Rothamsted Research, England
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Science and Technology/GSST, Ny Munkegade 120, building 1521, 8000 Aarhus C.

PhD defence
12183 / i43