This dataset includes measurements made during a laboratory-based study conducted between 10/2020 – 03/2021 on mineral amended soils with additions of two 13C labelled plant litters of contrasting quality. Data collected include: soil respiration (Carbon Dioxide (CO2))¬, total C content of bulk and soil fractions including mass and C recovery as a measure of the efficacy of the fractionation method, 13C enrichment of CO2 and soil fractions expressed as litter derived C, microbial data from bacterial (16S Small subunit ribosomal RNA) and fungal (internal transcribed spacer region 2) high throughput sequences. These data were collected to determine the relative effects of litter quality and soil mineralogy on the formation of soil C from plant material and may be useful to link plant inputs, soil microbes and soil mineralogy in the next generation of SOC models. Resolving the key fundamental mechanisms that control SOM persistence is crucial to optimise land management for SOC and predict soil C feedback to climate change. The experiment was part of the NERC project NE/S005137/2 Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/fddf7d9d-9694-4167-bbfe-8fb9d49f02a7