The Sättra Method – a Simpler Approach Towards Increased Soil Carbon Sequestration?

Can a light version of Conservation Agriculture be key to increasing carbon sequestration in the soil? The method known as the “Sättra Method” is practiced at and around the fields of Torsåker Farm, Axfoundation’s test farm and practical center for the sustainable food systems of the future. With reduced tillage, fewer working hours, lower carbon emissions from machinery and maintained or increased crop yields, the method certainly had its advantages. But does it also increase soil carbon sequestration? Together with researchers and farm advisors, Axfoundation set out to scientifically evaluate the method’s long-term effects on the ground. A journey that proved harder than anticipated.

One key indicator for soil health is soil organic carbon, which can be improved through certain agricultural techniques.

The Issue

It is well known that healthy soils are essential for the provision of ecosystem services, and soils’ importance for mitigating and adapting to climate change is increasingly being acknowledged. One key indicator for soil health is soil organic carbon, referring to the carbon stored in the organic matter of soil, which can be improved through certain agricultural techniques. However, which techniques farmers in Sweden should use and how well these contribute to an increase in carbon sequestration is still debated.

Our Solution

In order to evaluate the effects of one such carbon sequestration technique, Axfoundation teamed up with the farmer Mats Eriksson, who had practiced a light version of Conservation Agriculture for over 20 years – starting with one small field in 2000, and implementing it in over 120 fields two decades later.

The method ensures that the ground that will be used for spring crops is undisturbed from the threshing in the fall to the cultivation in the spring. This differs from the traditional farming system where the land is plowed or cultivated in the fall, even in fields that will be sown in the spring. According to Mats, the fields where the Sättra-method has been used show, among other things, maintained or even increased crop yields, lower carbon emissions from machinery, and reduced hours worked per hectare.

The Sättra Method

The Sättra Method could be classified as a “light version” of Conservation Agriculture. The method ensures that the ground is either planted directly after the harvest or left undisturbed until the cultivation in the spring. No plowing is done in the fall so there is no bare soil during winter. The straw from the crop is left on the field and contributes to building carbon storage in the soil.

According to farmer Mats Eriksson, who developed the method, the initial results show increased fertility and biological activity, reduced problems with soil erosion, increased mineralization, improved drainage and a maintained or increased harvest. This combined with reduced fuel consumption and fewer hours worked per hectare indicates that it is a method worth exploring further.

Conservation Agriculture

Conservation Agriculture is a combination of different sustainable farming methods that promote maintenance of a permanent soil cover, minimum soil disturbance and diversification of plant species. Methods the farmer can use include:

Avoid or reduce mechanical soil disturbance to an absolute minimum.
Keep the fields green for as large a part of the year as possible to sequester the carbon in the ground
through photosynthesis.
Grind down the cover crop into the soil just before sowing.
Direct drilling, i.e. seed placement without plowing.
Arrange the rotation of plants as efficiently as possible, this leads to a wide variety of crops, minimizing
the use of plant-protectant products and maximizing biodiversity.

Our Work

Axfoundation collaborated with researchers and farmers to analyze the effects of the Sättra-method in the fields at and around Torsåker Farm. The aim was to determine if this method could contribute to higher levels of soil organic carbon, resulting in increased carbon sequestration compared to conventional farming methods.

Results

After careful mapping of fields, researchers from the Swedish University of Agricultural Sciences (SLU) and Örebro University, set out to collect and analyze soil samples in the layers to 25 cm depth for evaluating potential differences in soil organic carbon.

An in-depth comparison was made between fields that had been farmed with the Sättra Method using reduced tillage for 5-20 years, and with reference fields. Unfortunately, no significant differences in the soil organic carbon could be found. Other physical and biological indicators that were measured, such as soil bulk density and total earthworm biomass, did not show any significant effects either.

The Swedish carbon market is in its infancy, and developing the system is important in order to verify what actually works. Our tests showed that even with long-term live trials using Conservation Agriculture techniques, individual variation between fields made it difficult to verify changes in soil carbon stocks. – Maria Lundesjö, Project Manager Future Food, Axfoundation

Progress Report 2023

Why did it fail?

The answer to this could be many things. It is difficult to verify differences in soil organic carbon stocks as annual changes are minor compared with total soil organic carbon stocks. It is possible that the potential effects on soil organic carbon were overshadowed by within-field variation, still after 20 years of practicing this method. The differences were therefore not statistically significant.

What did we learn?

Though the results of the project were disappointing, lessons were learned that could be implemented in further research. Verification of soil organic carbon response to different management regimes in farmer’s fields is a huge challenge and obstacle for current carbon farming initiatives. This project confirms that.

Going forward, Axfoundation is digging deeper, quite literally. In a continuing project, samples will be taken over a five-year period, making yearly measurements of several soil properties down to 90 cm depth. By doing so, we hope to come closer to correctly predicting and verifying carbon sequestration in soils. Such verification is an important parameter for a healthy market for Swedish carbon credits.

Successful or not, the results from the intensive study site will be made available for scientists to use in further research to speed up both market mechanisms and research.