What actually is soil health?

On 4 December, a workshop was held for SLU researchers focusing on the concept of soil health. The discussions centred on whether soil health is a useful concept and what it actually means. 

– The concept is good for communicating about soil issues because it emphasizes soil and land as a living organism that needs to be taken care of, and such an approach is good for raising the status of soil issues, said Leon Biundo, Production Manager at Alnarp's Agroecology Farm.

However, the understanding of soil health needs to be adapted to different soil types and land uses because we want soils to fulfil different functions depending on where they are and what they are used for. How we understand soil health is therefore closely linked to the respective soil function – and the desired soil functions differ between different land uses and their geographical location.

Challenges of using the same indicators for soils of different land uses

Many of the indicators proposed for the EU Soil Directive are aimed at agriculture, but the same indicators do not necessarily reflect what soil health is in forest soils because their physical, chemical and biological conditions as well as their intended functions are very different. In addition, indicators need to be able to show changes in soil functions. For example, soil basal respiration, meaning the release of CO₂ from the soil, is suggested as an indicator of soil biodiversity for the EU Soil Directive. While soil respiration is affected by the activity of microbes, it does not necessarily reflect a diverse microbial community.

Urban soils have their own unique challenges. Urban soils are often expected to fulfil very diverse functions while being exposed to a range of additional pressures, such as surface sealing or metal and organic contaminants. In addition to identifying the appropriate soil health indicators for urban soils, the key question is what exactly defines an urban soil and who holds the responsibility for addressing issues related to urban soils given their highly fragmented ownership.

– This is why it is important that soil health indicators are adapted to reflect different types of soils, so that we measure the right functions, said Johan Stendahl, researcher at SLU.

Several actors need to work together

Another dilemma that requires dialogue and collaboration is what information is useful for landowners, and for scientists to communicate what the values of the different indicators of soil health actually mean and what actions can improve them. Policies aim at a uniform assessment over a large geographical area, but strategies are implemented locally by landowners that are often facing more complex situations. Soil health but also strategies for improving soil health need to be contextualized spatially because certain measures can have different scales of effect for different soil types and land uses.

– Co-learning is critical! Different actors should be involved from the beginning to get a common direction on how to monitor soil health, and to gather data that makes it possible for landowners to act and adapt, said Tor-Gunnar Vågen, researcher at CIFOR-ICRAF in Kenya.