Research interests

Stress transmission in soil: Impact of soil conditions and tyre/track and loading characteristics on tyre/track-soil contact properties (stress distribution, contact area); Impact of soil structure and soil consistency on stress transmission.

Soil mechanical properties: Characterization of stress-strain relationships; Relating laboratory measurements to data from in situ wheeling experiments.

Soil compaction modelling: Combining the above mentioned aspects into simulation models; Development of decision support tools for risk assessment of soil compaction.

Soil tillage: Impacts of soil conditions and tillage implement properties on soil breakup during tillage (soil structure produced by tillage) and draught requirement.

Soil management: Impacts of soil management and soil compaction on soil functions, water and gas transport processes, and crop growth.

Current research activities include

Impact of long-term subsoil compaction on soil functions: This is investigated in the inter-nordic project POSEIDON which focuses on effects of subsoil compaction on soil pore functioning, water flow, and solute and gas transport processes.

Development of a web-based decision support tool for assessment of the risk of soil compaction due to agricultural field traffic: The tool is developed in collaboration with researchers from Aarhus University (DK) and the Bern University of Applied Sciences (CH), and incorporates recent developments in soil compaction modelling.

Tillage effects on soil organic carbon and phosphorus stratification and storage in Swedish soils (together with Ararso Etana).

Stress-strain behaviour and stress transmission in structured arable soil. This is investigated together with researchers from Aarhus University (DK) and INRA Montpellier (F).

Boards, committees, etc.

Chairman of the Working Group on Subsoil Compaction of the International Soil Tillage Research Organization (ISTRO)

Member of the organizing committee of the NJF seminar on Subsoil Compaction, to be held in Helsinki (SF), 6-8 March 2012.

Convener and host of the international exploratory workshop on Soil Compaction Modelling that was held in Zürich (CH), 12-13 October 2010.

Co-organizer of the PhD course on Soil Deformation: Modelling, Measurements, and Visualization, Research Centre Foulum, Aarhus University, Tjele (DK), 26 September - 2 October 2011.

Member of the scientific committee of the 2nd International Conference on Human Impacts on Soil Quality Attributes HISQA2, to be held in Isfahan (Iran). 

Selected publications

Keller T., Lamandé M., Peth S., Berli M., Delenne J.-Y., Baumgarten W., Rabbel W., Radjaï F., Rajchenbach J., Selvadurai A.P.S. & Or D. 2013. An interdisciplinary approach towards improved understanding of soil deformation during compaction. Soil & Tillage Research, 128, 61-80.

Naderi-Boldaji M., Alimardani R., Sharifi A., Hemmat A., Keyhani A., Loonstra E., Weisskopf P., Stettler M. & Keller T. 2013. Use of a triple-sensor fusion system for on-the-go measurement of soil compaction. Soil & Tillage Research, 128, 44-53.

Berisso F.E., Schjønning P., Keller T., Lamandé M., Simojoki A., Iversen B.V., Alakukku L. & Forkman J. 2013. Gas transport and subsoil pore characteristics: Anisotropy and long-term effects of compaction. Geoderma, 195-196, 184-191.

Etana A., Larsbo M., Keller T., Arvidsson J., Schjønning P., Forkman J. & Jarvis N. 2013. Persistent subsoil compaction and its effects on preferential flow patterns in a loamy till soil. Geoderma, 192, 430-436.

Keller T., Arvidsson J., Schjønning P., Lamandé M., Stettler M. & Weisskopf P. 2012. In situ subsoil stress-strain behavior in relation to soil precompression stress. Soil Science, 177(8), 490-497.

Keller T., Sutter J.A., Nissen K. & Rydberg T. 2012. Using field measurement of saturated soil hydraulic conductivity to detect low yielding zones in three Swedish fields. Soil & Tillage Research, 124, 68-77.

Keller T. & Dexter A.R. 2012. Plastic limits of agricultural soils as functions of soil texture and organic matter content. Soil Research 50(1), 7-17.

Keller T., Lamandé M., Schjønning P. & Dexter A.R. 2011. Analysis of soil compression curves from uniaxial confined compression tests. Geoderma, 163, 13-23.

Arvidsson J. & Keller T. 2011. Draught requirement during mouldboard ploughing as a function of soil strength. Soil & Tillage Research 111(2), 219-223.

Keller T. & Lamandé M. 2010. Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111(1), 54-64.

Keller T. & Håkansson I. 2010. Estimation of reference bulk density from soil particle size distribution and soil organic matter content. Geoderma 154(3-4), 398-406.

Keller T. & Arvidsson J. 2007. Compressive properties of some Swedish and Danish structured agricultural soils measured in uniaxial compression tests. European Journal of Soil Science 58(6), 1373-1381.

Keller T., Défossez P., Weisskopf P., Arvidsson J. & Richard G. 2007. SoilFlex: A model for prediction of soil stresses and soil compaction due to agricultural field traffic including a synthesis of analytical approaches. Soil & Tillage Research 93(2), 391-411.

Keller T., Arvidsson J. & Dexter A.R. 2007. Soil structures produced by tillage as affected by soil water content and the physical quality of soil. Soil & Tillage Research 92(1-2), 45-52.

Keller T. 2005. A model for prediction of the contact area and the distribution of vertical stress below agricultural tyres from readily-available tyre parameters. Biosystems Engineering 92(1), 85-96.