Carbon saturation revisited: Effects of aluminium oxides and soil structure on the carbon storage capacity of Swedish agricultural soils

Soils have a large potential to sequester carbon and thereby help mitigating climate change.

Based on recent research, which shows that oxalate-extractable aluminium (Alox) correlate strongly with soil organic carbon (SOC) contents, we hypothesize that Alox largely controls physical protection of SOC in soils and, thereby, the SOC sequestration potential.

To test this hypothesis we will 1) carry out long-term incubation experiments, both with intact soil columns and sieved soil from a field at Bjertorp with large natural variation in SOC, Alox and clay contents, and 2) test how general the observed correlations between SOC and Alox are, by measuring the Alox content in stored samples from the Swedish soil monitoring program “Soil and crop inventory of Swedish arable soils“.

To enable interpretation of the results from part 1 we will also measure root input, root phenotypic properties and column scale soil structure (i.e. characteristics of the macropore networks), which exerts a strong control on microbial accessibility to SOC. Macropore networks will  be quantified by X-ray tomography and image analysis.

Interpretation of the results from part 2 will be facilitated by quantification of silt-sized aggregation, which governs physical protection of SOC.

The results from this project will facilitate more climate smart agricultural management where investments in management for enhanced carbon sequestration are directed to soils where they will be most efficient.