Our research group aims at understanding impacts of soil management, soil compaction and natural processes on soil structure and associated soil functions.
Soil structure refers to the spatial arrangement of solids and pores. Soil structure governs a wide range of soil functions and processes and constitutes the living space for biological activity, which in turn are related to key soil ecosystem functions and services. In contrast to soil texture, which is determined by primary soil particles, soil structure is highly dynamic. Knowledge on how soil structure and its dynamics are affected by biophysical processes and human activities allows to develop strategies for sustainable soil use and management.
We are dedicated to an interdisciplinary research approach that integrates soil physics and mechanics, soil biological processes, plant science and agronomy. Our research involves spatial scales from soil pore to the field, and temporal scales from seconds to decades. We carry out work under controlled conditions at the model scale as well as in the field, and use both experimental approaches and modelling.
Listen to Professor Thomas Keller’s installation lecture “Soil structure - the functional architecture of soils".
Read more about our current research activities in the blue boxes below.
The Soil Mechanics and Soil Management research group at the Department of Soil and Environment at SLU.
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Soil stress measurements during wheeling experiments with forest machinery. Photo: Thomas Keller.
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Crack development due to simulated plant water uptake. Photos: Thomas Keller.
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A new platform to quantify crack evolution in soil due to simulated plant water uptake. Photo: Thomas Keller.
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Soil compaction due to agricultural operations is a serious threat to crop productivity and soil ecological functions in modern agriculture. The projected intensification of agriculture to meet food targets of a rapidly growing world population is likely to aggravate already acute problems of soil compaction. The real costs of soil compaction are borne by the cumulative loss of soil functionality such as yield loss following a compaction event, integrated over the time period until a soil has effectively recovered to its pre-compaction functionality. The overall goal of this research is to quantify compaction recovery rates and times, and to better understand the key mechanisms, including root growth, earthworm bioturbation, tillage, that control recovery rates. We established a long-term “Soil Structure Observatory” in Zürich, Switzerland (see www.sso.ethz.ch), to provide long-term observation data on soil structure evolution after disturbance by compaction.
Team: Tino Colombi, Thomas Keller
Collaborators: Dani Or, Siul Ruiz, Dani Breitenstein, Hans Wunderli, and Achim Walter, ETH Zürich, Switzerland; Peter Weisskopf, René Reiser, Viktor Stadelmann, Jan Rek and Marlies Sommer, Agroscope, Switzerland; Alejandro Romero-Ruiz and Niklas Linde, University of Lausanne, Switzerland.
Publications: Keller et al. 2017, Vadose Zone Journal 16; Colombi et al. 2017, Science of the Total Environment, 574; Colombi et al. 2018, Science of the Total Environment, 626; Romero-Ruiz et al. 2018, Reviews of Geophysics, 56, Barbosa et al., 2020, Geoderma, 374; Reiser et al., 2020, Journal of Plant Nutrition and Soil Science, 183
Website: www.sso.ethz.ch
Funding: Swiss National Science Foundation
Contact: thomas.keller@slu.se
Plants need to expand their root system in the soil to acquire water and nutrients. Thereby, roots modify soil structure. The rate of root growth and therefore whole plant development and soil structure formation is largely regulated by biophysical interactions between the root and the soil. We aim to develop a mechanistic understanding of processes and feedbacks along the soil-root-shoot continuum, and to identify functional root traits that ensure adequate crop performance under soil physical stress. Studies are carried out at the species and variety level. We use a broad set of methodologies including isothermal calorimetry and image-assisted analysis of plant growth, and combine experiments at various scales with modelling. One project aims at quantifying energy costs of root growth. Another project is “Improving soil structure in agro-ecosystems: Processes, interactions and feedbacks along the soil-root-shoot continuum governing soil structure formation (ImproSoSt)”.
Team: Tino Colombi, Thomas Keller
Collaborators: Martin Weih and Anke Herrmann, SLU; Pernilla Vallenback, Lantmännen Landtbruk; Norbert Kirchgessner, ETH Zürich, Switzerland.
Publications: Colombi et al. 2017, Plant Physiology 174; Colombi et al. 2017, Science of the Total Environment, 574; Colombi et al. 2018, Science of the Total Environment, 626; Colombi & Keller, 2019, Soil & Tillage Research, 191; Colombi et al., 2019, Plant Physiology, 180; Herrmann & Colombi, 2019, Plant Signaling & Behavior, 14
Funding: The Swedish Governmental Agency for Innovation Systems (Vinnova); The Royal Swedish Academy of Agriculture and Forestry (KSLA); Lantmännens Forskningsstiftelse, HM King Carl XVI Gustaf Foundation for Science, Technology & Environment; The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas)
Contact: tino.colombi@slu.se
Soil functions are manifold and range from regulations of biogeochemical and hydrological cycles to habitat functions for soil life and the provision of agricultural commodities. On-farm studies are needed to better understand how soil management and cropping systems affect soils and which management options that improve soil functions. In one project, we quantified a range of soil chemical, physical and biological properties in 60 Swiss fields representing three different management systems (20 fields per system): conventional tillage, organic farming, and no-till. Initial results show that both cropping and management system as well as intrinsic soil attributes such as soil texture have significant impacts on soil functions. In another project, we compare the effect of high and low diversity cropping systems on soil health on 20 farms (10 farms with high and 10 farms with low diversity) in Southern Sweden.
Team: Tino Colombi, Hanna Williams, Thomas Keller
Collaborators: Marcel van der Heijden, Sam Banerjee, Lucie Büchi, Jochen Mayer, Juliane Hirte, Agroscope, Switzerland; Johan Six, ETH Zürich, Switzerland; Raphaël Charles, FiBL, Switzerland.
Publications: Colombi et al., 2019, SOIL, 5; Banerjee et al., 2019, ISME Journal, 13; Büchi et al., 2019, European Journal of Agronomy, 109; Williams et al., 2020, Geoderma, 360, Etana et al., 2020, Acta Agriculturae Scandinavica, Section B – Soil & Plant Science, 70
Funding: Swiss National Science Foundation; The Royal Swedish Academy of Agriculture and Forestry (KSLA)
Contact: tino.colombi@slu.se
This research aims at developing a better understanding of post-tillage soil structural evolution and the temporal dynamics of soil pore space through measurements, experiments and mathematical models. The research will contribute towards a better understanding of the temporal dynamics of hydraulic properties of soil and therefore potentially lead to improved predictions of the impacts of soil management practices on water and solute transport, leaching of nutrients and pesticides.
Team: Reza Hosseinpour, Mats Larsbo, Thomas Keller
Collaborators: Nick Jarvis, SLU; Paul Hallett, University of Aberdeen, UK; Annette Dathe, Norwegian Institute of Bioeconomy, Norway.
Funding: The Faculty of Natural Resources and Agricultural Sciences, SLU
Contact: reza.hosseinpour@slu.se
This research is carried out within the EFFORTE project that aims at enhanced efficiency in forest operations, sustainable forestry, an increased forest growth, a cost-competitive bio-based industry and an acceleration of the regional economic development.
We are involved in a work package on trafficability that aims to establish a basis and to develop methodologies to predict trafficability of given forest stands or perennial skid trails prior to forest operations. We will review existing modelling approaches and perform wheeling experiments on forest soil.
Team: Maria Sandin, Thomas Keller
Collaborators: Philippe Ruch, FCBA, France; Noémie Pousse, ONF, France ; Tomas Nordfjell, SLU; Jori Uusitalo, Luke, Finland.
Publications: Vennik et al., 2019, Soil & Tillage Research, 186
Website: www.luke.fi/efforte
Funding: Bio-Based Industries Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme, grant agreement No 720712
Contact: maria.sandin@slu.se
Soil compaction by vehicular traffic modifies the pore structure and soil hydraulic properties. These changes potentially influence the occurrence of preferential flow. Our aim is to study the effect of compaction on soil hydraulic and transport properties and on the water flow pattern in soil.
Team: Mona Mossadeghi-Björklund, Mats Larsbo, Thomas Keller
Collaborators: Nicholas Jarvis and John Koestel, SLU
Publications: Mossadeghi-Björklund et al. 2016, Soil & Tillage Research 156; Mossadeghi-Björklund et al. 2019, Soil Use and Management, In press
Funding: The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas)
Contact: thomas.keller@slu.se
Conventional tillage homogenizes the soil and evenly distributes soil organic carbon (SOC) and phosphorus (P) in the ploughed layer, while reduced tillage or direct drilling stratifies them with more accumulation near soil surface. The aim of this project is to evaluate tillage impacts on the stratification and accumulation of SOC and P in Swedish long-term tillage experiments under conventional vs. reduced tillage. The final goal is to propose soil tillage strategies that enhance carbon sequestration with minimum risks for phosphorus losses.
Team: Ararso Etana, Thomas Keller
Publications: Martínez et al. 2016, Soil & Tillage Research, 163;
Funding: The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas), the Royal Swedish Academy of Agriculture and Forestry (KSLA)
Contact: ararso.etana@slu.se
Leaching of phosphorus is studied in a field experiment where we compare grass buffer strips with conventional tillage. The study is long-term to record changes of leaching with changing soil structure, organic matter and phosphorus accumulation in the soil profile.
Preliminary results show that the grass buffer strips reduced the loss of particulate-bound phosphorus via runoff. Removing of the plant material reduced the loss of dissolved reactive phosphorus (DRP), but to a lesser extent. Laboratory experiments on soil columns showed that repeated freezing and thawing may lead to elevated leaching of DRP from the grass buffer strips.
Team: Ararso Etana
Collaborators: Barbro Ullén, SLU.
Funding: The Swedish Farmers’ Foundation for Agricultural Research (SLF)
Contact: ararso.etana@slu.se
A reduction of phosphorus (P) losses from Swedish agricultural land is necessary to meet the “zero eutrophication” target. A great proportion of P losses are associated with P bound to particles in drainage water. However, detailed information on the nature of this P is lacking.
We hypothesize that particulate P in drainage water is a combination of (i) P associated to clay mineral particles, which may be lost due to poor soil structure as influenced by cropping/tillage, and (ii) P associated with Fe-oxyhydroxide colloids, which may form during reduction-oxidation in the subsoil as influenced by soil drainage.
We will use a range of modern techniques to characterize colloidal P in drainage water on samples collected at experimental fields in Southern and Central Sweden. We will investigate whether particle-bound P losses can be predicted from the content and mineralogy of fine clay, and from soil dispersion tests.
Team: Ararso Etana
Collaborators: Magnus Simonsson, Jon Petter Gustafsson, Geert Cornelis, Daniel Lundberg and Helena Aronsson, SLU.
Funding: The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas)
Contact: ararso.etana@slu.se
Terranimo® is a web-based tool for evaluating soil compaction risks caused by agricultural machinery, available at www.terranimo.se. We will refine Terranimo® by including new functionality that allows evaluation of repeated wheeling and by improving the user interface in an on-going project (2018-2021).
Team: Thomas Keller
Collaborators: Per-Anders Algerbo and Mikael Gilbertsson, RISE, Sweden; Marcus Willert, HIR Skåne, Sweden; Matthias Stettler, School of Agricultural, Forest and Food Sciences (HAFL), Switzerland; Per Schjønning and Mathieu Lamandé, Aarhus University, Denmark; Thomas Albert, afca, Switzerland.
Website: www.terranimo.se
Publications: Keller & Arvidsson 2016, Soil & Tillage Research 155; Schjønning et al. 2015, Soil & Tillage Research 152; Stettler et al. 2014, Landtechnik 69; Keller et al. 2007, Soil & Tillage Research 93; Keller 2005, Biosystems Engineering 92; Lima & Keller, 2019, Soil & Tillage Research, 189, Keller et al., 2019, Soil & Tillage Research, 194; ten Damme et al., 2019, Soil & Tillage Research, 194, Schjønning et al., 2020, Soil & Tillage Research, 200
Funding: The Swedish Farmers’ Foundation for Agricultural Research (SLF)
Contact: thomas.keller@slu.se
Earthworms are soil ecosystem engineers and play a key role for soil processes including aggregation, nutrient cycling and carbon turnover. Earthworms create burrows in their search for food by either expanding cavities or ingesting soil, and produce casts within the soil or on the soil surface. The transporting and mixing of soil by earthworms is known as bioturbation and one of the key natural processes that shapes soil structure.
The amount of transported soil by earthworms is considerable and can be several hundred tonnes per hectare and year. The aim of this research is to understand how earthworm burrowing activity is affected by soil conditions. In particular, we aim at quantifying burrowing rates as a function of soil mechanical conditions and soil organic carbon concentration. For this, we combine experiments at various scales.
Team: Elsa M. Arrázola Vásquez, Maria Sandin, Mats Larsbo, Thomas Keller
Collaborators: Yvan Capowiez, INRA Avignon, France; Astrid Taylor, SLU.
Funding: The Faculty of Natural Resources and Agricultural Sciences, SLU
Contact: elsa.arrazola@slu.se
Read about our previous research projects here.
The environmental monitoring programme “soil compaction” was started in 2003, aiming at assessing the temporal evolution of the physical quality Swedish arable soils.
More information is available here (in Swedish).
We currently manage 12 long-term field experiments where we investigate effects of different soil management systems on soil quality and crop productivity.
Department of Soil and Environment
thomas.keller@slu.se
Arrázola-Vásquez E., Larsbo M., Capowiez Y., Taylor A., Sandin M., Iseskog D. & Keller T. 2022. Earthworm burrowing modes and rates depend on earthworm species and soil mechanical resistance. Applied Soil Ecology, 178, 104568.
Colombi T., Chakrawal A., Hermann A.M. 2022. Carbon supply–consumption balance in plant roots: effects of carbon use efficiency and root anatomical plasticity. New Phytologist, 233, 1542-1547.
Keller T., Sandin M., Colombi T., Horn R. & Or D. 2019. Historical increase in agricultural machinery weights enhanced soil stress levels and adversely affected soil functioning. Soil & Tillage Research, 194, 104293.
Sjulgård H., Colombi T., Keller T. 2022. Spatiotemporal patterns of crop diversity reveal potential for diversification in Swedish agriculture. Agriculture, Ecosystems and Environment, 336, 108046.
Sjulgård H., Iseskog D., Kirchgessner N., Bengough A.G., Keller T. & Colombi T. 2021. Reversible and irreversible root phenotypic plasticity under fluctuating soil physical conditions. Environmental and Experimental Botany, 188, 104494.
Williams H., Colombi T. & Keller T. 2020. The influence of soil management on soil health: an on-farm study in southern Sweden. Geoderma, 360, 114010.