Soil Mechanics and Soil Management

Soil compaction: towards reduced risks of soil compaction in agriculture, forestry and construction work

The use of agricultural, forestry, construction and other off-road vehicles can cause soil compaction when the induced mechanical stresses exceed the internal strength of soil. Consequences of compaction include decreased plant productivity, reduced carbon inputs to soil, reduced water infiltration and storage, and potentially increased greenhouse gas emissions. While compaction can occur within seconds, compaction recovery may take decades. Hence, prevention of compaction is of high priority.

Our research aims at improved description of soil mechanical behaviour as a basis to propose sustainable soil management that minimises compaction risks. In-situ soil stress measurements for different combinations of machinery and soil conditions help us to better understand how stress propagates in soil. In the laboratory, we quantify soil stress-strain behaviour to evaluate how soil characteristics and moisture conditions affect soil deformation and soil strength, and to describe relationships between soil deformation and changes in functional soil properties. Long-term field experiments are used to monitor how soil structure recovers following compaction. We combine experimental work with simulation studies to generalise our findings and to predict compaction risks for different soil management scenarios and for future climatic conditions.

On-going research project involve collaboration with farmers and advisers. For example, we characterise soil mechanical properties and continuously measure soil moisture in several farmer fields in major Swedish cropping areas to quantify the spatial and temporal dynamics of compaction risks in Sweden. We discuss our findings with farmers and advisers, and together develop sustainable soil management strategies.

Selected publications: Torres et al., 2024, Soil & Tillage Research 244, 106225; Keller et al., 2019, Soil & Tillage Research 194, 104293; Keller & Or, 2022, Proceedings of the National Academy of Sciences 119, e2117699119; Parvin et al., 2022, Soil Security 6, 100044.

On-going projects

• Implementation of soil compaction risk assessment system – end user’s evaluation of potentials and barriers (SoCoRisk)
• Mapping and alleviating soil compaction in a climate change context (SoilCompaC)
• Assessment methodologies and mitigation measures for the impacts of road projects on soils (ROADSOIL)
• Soil compaction risks in Sweden: spatio-temporal assessment under current and future climate; Environmental Monitoring “Soil compaction”

Funding: Swedish Research Council for Sustainable Development (Formas), Swedish farmers’ foundation for agricultural research (SLF), European Union´s Horizon 2020 research and innovation programme through ICT-AGRI-FOOD and through EJP Soil; Swedish Environmental Protection Agency.

Team: Lorena Chagas Torres; Maria Sandin; Konsta Sarvela, Ararso Etana, Daniel Iseskog, and Thomas Keller

Contact person: Lorena Chagas Torres, lorena.chagas.torres@slu.se

Soil provides habitat for an unimaginable number and diversity of organisms and supports numerous functions and ecosystem services, including plant production, nutrient cycling, and water and climate regulation. Land use and soil management have strong impacts on overall soil health and functioning. Soil management can be a driver of soil degradation, but soil management can also enhance soil functioning and is key to solving one of today’s largest challenges: to feed a growing population while minimizing negative impacts on the environment. The changing climate, with more frequent and intense extreme weather events (droughts, floods), adds to the challenge.

The aim of our research is to understand links and feedbacks between soil management, climate, soil health, and soil ecosystem services. We use (long-term) field experiments, on-farm studies in collaboration with farmers, and long-term data records in (national) databases to address specific research questions. We consider a wide array of soil and crop management but focus on impacts of tillage, crop rotations including cover crops, organic amendments, and liming. Soil health or soil quality is evaluated by measuring different soil indicators, involving physical, chemical and biological aspects. Crop productivity, both in terms of yield level and yield stability, is a central aspect in our analyses, but we also consider other soil functions and processes (e.g. soil carbon stocks, greenhouse gas emissions) to identify synergies and trade-offs between soil ecosystem services.       

Selected publications: Sjulgård et al., 2024; Agricultural Systems 211, 103757; Sjulgård et al., 2022, Agriculture, Ecosystems & Environment 336, 108046; Williams et al., 2020, Geoderma 360, 114010; Etana et al., 2020, Acta Agriculturae Scandinavica B 70, 333-340.

On-going projects: Soil management for improved soil quality and higher yield stability under extreme weather; Analysis of historical data to evaluate effects of precipitation and temperatures on Swedish crop yields; A simple method for investigating phosphorous leaching from agricultural soils; Soil health for increased carbon sequestration and adaptation to a changing climate; The capacity of crops for enhanced carbon allocation to soil in a changing climate – synergies and trade-offs (“C4C”); Mixed cultivar systems to mitigate drought effects on Nordic crop production (“Rootmix”); Long-term effects of structural liming on phosphorus losses from arable land and the impact of tillage.

Funding: Swedish farmers’ foundation for agricultural research (SLF); Swedish Board of Agriculture (Jordbruksverket); Swedish Research Council for Sustainable Development (Formas), Novo Nordisk Foundation, Swedish Royal Academy of Forest and Agricultural Sciences (KSLA); European Union´s Horizon 2020 research and innovation programme through EJP Soil.

Team: Hanna Sjulgård, Ararso Etana, Lorena Chagas Torres, Elsa Arrázola Vásquez, Pascal Benard, Konsta Sarvela, Mats Larsbo, and Thomas Keller

Contact person: Hanna Sjulgård, hanna.sjulgard@slu.se

Earthworms are recognized “soil ecosystem engineers”. Through their burrowing activity, they create pore space and mix soil, which is of key importance for many soil processes and functions. Earthworm burrowing supports soil structure maintenance and facilitates water regulation, root proliferation, carbon cycling and nutrient availability.

Our research aims at quantifying earthworm burrowing rates, i.e. how fast earthworms burrow, at how burrowing rates are affected by soil conditions and vary between earthworm species, and at how much energy earthworms need to burrow. We focus primarily on soil physical constraints for burrowing, such as temperature, soil moisture and bulk density – the latter two governing soil mechanical resistance.

We use experimental approaches in the laboratory to study earthworm behaviour and to quantify earthworm burrowing and associated energy costs at time scales of days, and perform experiments under field conditions to monitor burrowing over several months. Our research contributes to improved quantitative understanding of how earthworm burrowing is affected by changes in land use, soil management and climate, which is fundamental knowledge needed to estimate consequences on earthworm-mediated soil processes and functions.

Selected publications: Arrázola-Vásquez et al., 2024, European Journal of Soil Biology 121, 103619; Arrázola-Vásquez et al., 2022, Applied Soil Ecology 178, 104568; Arrázola-Vásquez, 2023, Doctoral Thesis No 2023:34.

On-going projects: Bioturbation by earthworms in Sweden: impacts of climate and land use; Quantifying the energy costs of earthworms burrowing activity under a climate change scenario

Funding: Swedish Research Council for Sustainable Development (Formas), Swedish Royal Academy of Forest and Agricultural Sciences (KSLA)

Team: Elsa Arrázola Vásquez, Rebecca Naomi ter Borg, Mats Larsbo, Daniel Iseskog, and Thomas Keller

Contact person: Elsa Arrázola Vásquez, elsa.arrazola@slu.se

Crop production is driven by interactions between plant physiology, soil physical, chemical and biological processes, climatic conditions, and agricultural management. The goal of our research is to uncover mechanisms at the root-soil interface underpinning long-term crop productivity and carbon sequestration.

We are committed to an interdisciplinary approach that integrates plant and soil science with agronomy and ecology. We combine experimental work at scales from the single root to the field with theoretical approaches.

On-going projects focus on the potential of mixed cultivar systems consisting of shallow and deep rooting cereals to increase resource use efficiency and climate resilience of Nordic cropping systems, and on the potential of cover crops, mixed cultivar systems, and specific root ideotypes to enhance carbon inputs into soil. Moreover, current research aims at identifying root traits that can improve crop growth on dry and/or compacted soil by elucidating links between root-soil biophysics and whole plant physiology.

Our research contributes to fundamental new knowledge as a basis for enhancing overall functioning of arable soils and for securing crop productivity.

Selected publications: Colombi et al., 2024, Trends in Plant Science 29, 856-864; Colombi et al., 2022, New Phytologist 233, 1542-1547; Colombi et al. 2019, Plant Physiology 180, 2049-2060.

On-going projects: Mixed cultivar systems to mitigate drought effects on Nordic crop production (“Rootmix”); The capacity of crops for enhanced carbon allocation to soil in a changing climate – synergies and trade-offs (“C4C”); Crop production in a changing climate: The role of soil management and crop selection in mitigating extreme weather impacts under Swedish conditions.

Funding: Novo Nordisk Foundation, Swedish Research Council for Sustainable Development (Formas), Lantmännen Research Foundation, Swedish Royal Academy of Forest and Agricultural Sciences (KSLA); Stiftelsen JTI, Swedish farmers’ foundation for agricultural research (SLF) . 

Team: Pascal Benard, Elsa Arrázola Vásquez, Hanna Sjulgård, Lorena Chagas Torres, Mats Larsbo, Daniel Iseskog, and Thomas Keller

Contact person: Thomas Keller, thomas.keller@slu.se

Addressing research questions often requires specific, customized experimental set-ups. We have our own laboratory where we can design and create completely new experimental set-ups. We use computer-aided design (CAD) to sketch components or entire experimental set-ups, which are then produced by in-house 3-D printing or using contract manufacturing. We combine the manufactured parts with optical sensors for imaging, and loggers for data acquisition into experimental set-ups.

We use open source solutions (e.g. Arduino, Raspberry pie) to combine and control various parts of set-ups. Some of our customized set-ups are installed inside our own climate chambers, which allows us to do experiments with plants or earthworms under controlled environmental conditions. We have also designed and produced specific measurement equipment, for example for measurement of soil mechanical properties.

We are happy to assist scientists from other research groups – if you are interested, get in contact with us.

Selected publications: Sjulgård et al., 2021, Environmental and Experimental Botany 188, 104494; Colombi et al., 2021, Soil & Tillage Research 205, 104769; Arrazola et al., 2022, Applied Soil Ecology 178, 104568.

On-going projects: The lab facilities and resources are important for several of our on-going research projects.

Contact person: Daniel Iseskog, daniel.iseskog@slu.se