Deep in the roots of carbon sequestration
Soil can play a major role in mitigating the impact of climate change by sequestering carbon from the atmosphere. We spoke to Professor Thomas Kätterer about his research into the impact of different management practices on soil carbon sequestration, and its wider relevance in helping meet emissions reduction targets.
The process of carbon sequestration is the focus of a great deal of attention in research, as countries across the world seek to reduce carbon emissions and mitigate the impact of climate change. Plants take in carbon dioxide (CO2) from the atmosphere and form biomass, part of which then goes into the soil, where it is stored for sustained periods. “This mitigates the effects of climate change,” explains Thomas Kätterer, Professor in ecosystem ecology at the Swedish University of Agricultural Sciences (SLU). Different crop management practices affect the rate at which CO2 is transported from the atmosphere to soil, a topic central to Professor Kätterer’s research. “We’re looking at how different management practices affect this carbon flux. What management practices favour the storage of carbon in the soil?” he asks. “Building up carbon storage also has other positive effects, including on plants, microbes, fungi and animals that live in soil.”
Carbon sequestration
As the Principal Investigator of a project backed by the Swedish government research council (Formas), Professor Kätterer is now looking to build a fuller picture of the rate at which carbon is sequestered under different crop management practices. Certain practices can lead to an increase in soil carbon or organic matter content, which many governments are keen to encourage. “In Sweden for example farmers are subsidised to use cover crops,” outlines Professor Kätterer. These cover crops grow later in the year after the harvest of main crops, leading to the formation of new biomass that increases the level of soil organic matter, alongside other benefits. “When you have these cover
crops it also reduces erosion problems, as rains in Autumn and Winter transport particles to the waterways, and degrade the soil, by transporting the top soil within the landscape,” explains Professor Kätterer. The project team is now investigating the effects of this practice on rates of carbon soil sequestration, as well as assessing the impact of other practices, such as sowing and rotating different crops. Carbon accumulation in soil is a slow process and annual changes are relatively small, so Professor Kätterer says many years’ worth of data are needed to see measurable changes. “A huge amount of carbon is already there, and changes have to accumulate over a long time before we really see a measurable effect, so we need long-term
studies,” he acknowledges. Researchers are using data from long-term field experiments (LTEs) conducted at different locations, while soil samples are taken from 2,000 fields in Sweden in a long-term monitoring programme. “Researchers go back to the same spot in a field every ten years or so and measure the changes that have occurred,” says Professor Kätterer.
This provides a rich source of data going back several decades in some cases. One experiment started in the town of Ultuna in 1956 for example, with researchers looking at the impact of different treatments within a field on crop yields, and some marked variations in soil carbon content can now be seen. “We measured almost 4 times more
carbon in the soil in the highest treatment compared to the lowest treatment. We have looked at the response of the maize grown over the last 20 years, and have been able to relate maize productivity to changes in soil carbon,” outlines Professor Kätterer. A further important aim in the project is to disentangle the effect of increased nutrient levels from the impact of changes to the soil structure.
“If you increase soil organic carbon you also increase levels of nitrogen and phosphorus, which are constituents of organic material in the soil,” explains Professor Kätterer. A higher turnover of soil organic matter leads to the delivery of more nutrients to crops and increased levels of soil organic matter.
Researchers have been working to separate the impact of this on maize yields from the
says Professor Kätterer. “There is a lot of interest in effective tools to estimate the impact of different management practices on greenhouse gas emissions and carbon sequestration,” he continues. The project team is now working to improve and refine these models further.
“From the LTEs we parameterise models that we then use at the regional scale, or scale the effect up to the country scale,” says Professor Kätterer. “We use different kinds of models, and are building a platform to run models on different data series.”
Researchers are sharing their findings with the agricultural sector, while Professor Kätterer and his colleagues also work together with Sweden’s Environmental Protection Agency. The data they provide on carbon stock changes in Swedish agricultural land is used
“ We’re looking at how different management practices affect this carbon flux . What management practices favour the storage of carbon in the soil?”
physical effects of improved soil structure, which enhances the water-holding capacity of the soil. “We were able to show that the main factor behind increased maize yields was changes in the physical properties of the soil, rather than increased delivery of nutrients,” says Professor Kätterer. Alongside working with data from LTEs, Professor Kätterer and his colleagues are also conducting flux measurements, measuring the exchange of gases between the surface and the atmosphere.
“We have chambers which cover the soilwith or without vegetation, depending on the specific fluxes we are interested in. We can measure the exchange of gases at a small scale,” he explains.
Climate models
These measurements can then be used to inform models of the underlying processes behind soil carbon sequestration, which will be invaluable in terms of understanding which practices can mitigate the impact of climate change. There is also wider interest in these models from beyond the agricultural sector,
every year in compiling the national climate report, illustrating the wider importance of this research. “The national climate report is then delivered to the EU, UN and other bodies,” says Professor Kätterer. This work is very much ongoing, and Professor Kätterer plans to pursue further research in this area, aiming to build a deeper picture of the effects of different land management practices.
“From the soil monitoring programmes and the LTEs we can relate changes in soil properties - like soil organic carbon - to how the land was managed,” he outlines.
The project team is also using other sources of information, including satellite data and public databases, to understand the historical background and then relate that to the changes that researchers see in soil samples today. This can then inform management practices and advice to the agricultural sector, helping farmers improve soil quality and mitigate the impact of climate change.
“The models we are developing can provide valuable insights for farmers,” stresses Professor Kätterer.
Carbon sequesT raT ion in sweD ish CroPlan D soils
Project objectives
This project aims to generate new applicable knowledge from the information we have gained from studies on Swedish long-term field experiments, national soil monitoring, and other databases, and integrate it into a novel modeling approach to advance our estimates of the carbon sequestration potential in agricultural soils under Swedish conditions.
Project Funding
This project is funded by the Swedish Research Council under Grant Number 2022-00214_Formas.
https://www.vr.se/english/swecris. html?project=2022-00214_Formas#/
Project Team
Contact Details
Project Coordinator:
Professor Thomas Kätterer
Department of Ecology P.O. Box 7044 750 07 UPPSALA T: +4618672425
e: thomas.katterer@slu.se w: https://www.slu.se/en/ew-cv/thomaskatterer2/
https://www.lantbruksforskning.se/projektdatabasen/ fang-och-mellangrodors-bidrag-till-kolinlagringmullens-betydelse-for-skord-och-skordestabilitet/ ff80818182a02a440182d5881d4b084c/ https://ejpsoil.eu/soil-research/carboseq/ https://ejpsoil.eu/soil-research/eom4soil/intodialogue/simple
https://www.nibio.no/en/projects/captureassessment-of-cover-cropping-as-climate-action-incereal-production-in-norway?locationfilter=true
and an elected fellow of The Royal Swedish Agricultural Academy. He has a background in agronomy, soil science, ecology, and environmental sciences. His research focuses on carbon and nutrient cycling in agroecosystems, particularly agricultural management practices related to mitigation and adaptation to climate change.
