Original data for the manuscript "Tillage-induced organic matter increase in a grassland subsoil across fractions, horizons, and land use change"

Soil samples were gathered from a plowed cropfield and a neighbouring permanent grassland to analyse land use-induced variations in soil organic matter (SOM) content and composition. The sampling aimed at the "Atop", "Asub", and "ACk" horizons up to 80 cm depth. The stable and labile SOM pools were separated by dividing the fine fraction (<63 microns) and the aggregates + sand, respectively. Particle size distribution, pH, and EC were measured in bulk soil; total and inorganic carbon, nitrogen, and sulfur contents were measured in both soil and fractions; and the composition of SOM was measured in the fractions using Fourier Transform Infrared Spectroscopy.