The potential of agricultural soils to offset human-induced CO2 emissions – and why soil structure is important for that

Soil is a natural resource that provides valuable ecosystem services for human life and society, e.g., water and nutrient storage, water filtering, food and fiber production, cultural heritage archiving, substrate for housing and infrastructure etc). In brief, soils are vital for human existence on our planet. In addition to that, soils store large amounts of organic carbon (C). Globally, approximately three times more C is stored in the top meter of soils than in all the vegetation, and twice as much C as in the atmosphere. This means that small changes in soil C stocks can have significant impacts on the atmospheric concentration of carbon dioxide (CO2) and methane (CH4). On the other hand, actively increasing the amount of C stored in soil can help offset human-induced CO2 emissions, stabilize the climate and ensure food security.

Following human activity, such as unsustainable agriculture, soil organic carbon (SOC) contents are declining in many soils. Against the background, that SOC is critical to the majority of services mentioned above, this issue becomes particularly critical with regard to an estimated increasing human population. The European Commission (EC) included SOC storage in their framework for the protection of important soil functions, and meanwhile, declining SOC is considered a European (and global) threat. Achieving sustainable soil management in the European Union (EU) is therefore crucial for several of the planned actions within the European Green Deal. The important role of soil in the future agricultural policy is, among others, included in the Farm to Fork strategy, aiming to make food systems fair, healthy, and environmentally friendly. Soil protection is further given attention in strategies on environmental protection (Biodiversity strategy) and climate change (Climate Law).

In my lecture, I will present different aspects of my research in which I use both already published data, own observations, as well as mathematical modelling in order to better understand the influences of soil management on SOC stocks and the underlying processes that might help to sequester more C in agricultural soils. I will show results of a meta-analysis on how tillage influences SOC stocks and, more specifically, the depth distribution of C in the soil. On a much smaller scale, I will show how biological activity, i.e. growth of plant roots and earthworm bioturbation affects the SOC stored in the soil, primarily by their influence on the soil´s structure. In addition to that, I will present the performance of a model that, for the first time, links the two-way interactions between SOC contents and soil structure dynamics – a fact that has been ignored by SOC models so far, but is that has to be included e.g., when making projections on the fate of C under a future climate. I will further introduce how this work is further developed within projects related to EJP SOIL program. In those projects, I work on extending the above-mentioned model towards crop growth and soil hydrology and, in particular. This is needed in order to better describe C that is brought into the soil by plant roots. This work is in strong collaboration with a consortium of researchers across Europe, which will make outputs representative on the European level.