Organic matter stabilisation during paddy soil development depending on soil type

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The aim of project is to identify the role of microaggregation, organo-mineral complexes, and charred organic carbon for the stabilisation of organic carbon in paddy soils. A method consisting of a combination of physical (particle-size and density) and chemical fractionation methods will be adapted to each soil type specifically to isolate aggregates and organo-mineral complexes in soil-type specific soil organic matter (SOM) fractions. The isolated fractions will then be analyzed for the chemical composition of the organic matter by solid-state 13C NMR spectroscopy and specifically for the hydrolysable carbohydrate content by GC-MS. The age of the stable organic matter in selected fractions will be assessed by radiocarbon analysis. The organo-mineral associations will be characterized by selective or total removal of minerals and organic substances in combination with analysis of specific surface area. Soil fractions will be investigated by SEM and NanoSIMS to elucidate the composition of microaggregates and organo-mineral complexes. This will enable us to understand the influence of the parent soil type on aggregation and soil organic carbon stabilisation in dependence of e.g. type and content of iron oxides, and to evaluate the contribution of the different SOM stabilisation processes during paddy soil formation.