Humus Observation from Space: A Giant Peek into Mankind

The humus content of soils is one of the most important indicators of soil fertility. Detecting humus changes by sampling soils is very time-consuming and expensive. A new method enables the direct observation of humus changes with satellite images.

Posing a threat to soil fertility and sustainable farming, the humus stock of agricultural soils in Germany is declining. Researchers from the Thünen Institute of Farm Economics have achieved a groundbreaking milestone by demonstrating that changes in humus content can be observed from space. This pioneering study used data from the Bavarian State Research Centre for Agriculture (LfL), gathered over several years from 100 arable sites in Bavaria.

The team leveraged satellite imagery to detect subtle changes in soil color, as humus-rich soil appears darker. However, isolating these signals required advanced filtering techniques to address interferences like vegetation cover and soil moisture. This labor-intensive process was led by Tom Brög, a scientist from the Remote Sensing Group at the Thünen Institute.

By comparing satellite data with ground-based observations, the researchers could identify fields where humus levels were increasing or decreasing with remarkable precision. While this method excels in distinguishing trends over extended periods—spanning several years to decades—it cannot yet provide exact rates of humus accumulation or loss.

Instrument for carbon farming

The groundbreaking method developed by researchers at the Thünen Institute has far-reaching implications beyond soil fertility—it provides a critical foundation for carbon farming, an innovative approach to climate protection. By leveraging this technology, farmers can not only enhance soil health but also contribute to reducing greenhouse gas emissions while reaping financial rewards.

Carbon farming aims to mitigate climate change by encouraging practices that increase humus content in soils, effectively sequestering carbon. To make this approach viable, it’s essential to quantify and verify the reduction in greenhouse gas emissions achieved through humus build-up. The European Council recently approved a regulation enabling the generation of CO₂ certificates for the voluntary carbon market. These certificates offer farmers financial incentives for implementing practices that build humus or lower soil-based greenhouse gas emissions.

For these certificates to maintain credibility in climate protection efforts, independent verification of humus changes is crucial. The Thünen Institute’s satellite-based method provides a reliable solution. High-resolution satellite images, increasingly available for soils worldwide, allow for precise and independent assessments of humus formation. This ensures that claims about carbon sequestration and greenhouse gas reductions are transparent and trustworthy.

Humus for soil health and climate

Humus plays an essential role in maintaining soil stability and supporting the intricate ecosystem of life beneath the surface. Beyond its agricultural importance, humus is a key factor in climate regulation. When humus is lost, it contributes to carbon dioxide emissions, exacerbating climate change. Conversely, increasing humus content in soils can help sequester carbon, offering a natural solution to mitigate greenhouse gas emissions.

The ability of soils to lose or build up humus depends on several factors, including soil management practices, historical land use, and climate conditions. Poor soil management can lead to humus degradation, while sustainable practices can promote its accumulation. Climate factors, such as temperature and rainfall, also significantly influence humus dynamics.

However, detecting these changes presents a considerable challenge. Within a single field, humus content can vary greatly due to natural soil heterogeneity. Additionally, changes in humus stocks are often minuscule, typically noticeable only in the second decimal place even after several years. This makes conventional methods, like repeated soil sampling, both time-intensive and imprecise for monitoring humus dynamics.

Unlocking the Future of Soil and Climate Health from Space

The innovative use of satellite imagery to monitor humus content marks a transformative step in soil science and climate action. By enabling accurate, large-scale observation of humus changes, researchers from the Thünen Institute have unlocked a cost-effective and efficient method to track soil health.

As satellite technology continues to evolve, this method offers a scalable solution for monitoring soil health worldwide. By bridging the gap between space technology and sustainable land management, this innovation paves the way for a more resilient and climate-conscious agricultural future.

Press release: https://www.thuenen.de/de/newsroom/presse/aktuelle-pressemitteilungen/detailansicht/humusbeobachtung-aus-dem-all

Original publication
Broeg, T., Don, A., Wiesmeier, M., Scholten, T., & Erasmi, S. (2024)
Journal: Global Change Biology
Article Title: Spatiotemporal Monitoring of Cropland Soil Organic Carbon Changes From Space
Article Publication Date: 09-12-2024
DOI: https://doi.org/10.1111/gcb.17608

Contact
Dr. Stefan Erasmi (Project Leader)
Thünen Institute of Business Administration, Braunschweig
Phone: +49 531 2570 2052
Mail: stefan.erasmi@thuenen.de

Further information
Projekthomepage

Spokesperson
Nadine Kraft
Thünen-Institut
Bundesallee 50
38116 Braunschweig
Phone: 0531 25 70 18 65
Mob: 0151 15 29 08 50
Mail: nadine.kraft@thuenen.de
Web: www.thuenen.de