Increasing crop rotational diversity, e.g., by including grass-clover ley crops, can increase soil organic carbon (SOC) and support climate change mitigation and adaptation, with economic and environmental co-benefits. Here, we apply a method for using large and continuously updated geospatial datasets on (i) agricultural land use and (ii) soil properties, from the Swedish national soil inventory, to analyze how grass-clover (ley) cultivation in rotation with annual crops influences SOC content and soil structure quality (SOC/clay ratio). The results suggest a positive correlation between the occurrence of ley in crop rotations and SOC content. The method used in this study can build on and complement long-term field experiments and can enable the use of spatially explicit soil structure indicators for mapping and analyzing effects of land management, providing input to inform development and implementation of policies for land-based climate change mitigation.