Main research question/goal
This PhD research investigates the relative contribution of belowground versus aboveground biomass to the buildup of stable soil organic carbon (SOC) pool. This ratio appears to be a key factor that decides whether plant tissue carbon will take the form of either mineralised CO2 or as stabilised SOC. It is also well known that P deficiency induces a reduction in primary root growth and promotes lateral root and root hair growth, possibly promoting the formation of aggregate occluded SOC. This incorporation of C into aggregates, especially micro-aggregates, is an important mechanism for C sequestration in the long term, as it physically protects SOC from microbial decomposition. Amongst other mechanisms, this physical occlusion could explain why root-derived C is less prone to decomposition than aboveground-derived C.Research approach
The purpose of this research is to track the fate of maize-derived SOC, more specifically the root-derived C, that is physically protected in the soil. We quantify stabilised root-derived SOC by physical fractionation and 13C isotope analysis. We compare different maize varieties and soil textures in pot experiments as well as in existing field experiments to account for long-term effects.Relevance/Valorisation
Crop residues not only return organic matter and nutrients to the agricultural soil, but also form a potentially interesting resource for other uses such as renewable energy production. Because biomass resources are not infinite, their efficient and sustainable use is important. Therefore the contribution of aboveground- as well as belowground-derived crop residues to the stable SOC pool should be known. Better understanding of the turnover kinetics and physical protection of the belowground crop residues in micro-aggregates is particularly important.