Soil structure has been degraded by conventional arable farming resulting in reduced capacity of soil to store carbon, water and nutrients, with effects that impact on crop production and environmental risks such as flooding. This project will use state-of-the-art metabolomic and metagenomic analyses to determine the mechanisms of chemical and microbial interactions involved in the aggregation of soil particles into structures that restore and deliver high soil quality. It will focus on how the use of grass-clover rotations improves soil structure through microbial and chemical interactions in soils using plots established in replicated conventionally managed arable fields. Using a portable mass-spectrometer metabolonic ‘fingerprints’ will be developed for extracts of soil immediately after removal from the field plots, for soil crumbs of different sizes. In parallel, the microbial communities found in crumbs of different sizes and will be determined by metagenomic analyses. The work will help resolve the microbial and biochemical components that are important for holding soil crumbs together to guide future trait selection in crops and in soil management to restore the larger soil crumb structures that are important for good soil health.