Tillage Intensity Shapes Soil Carbon Stabilization Pathways Differently in Contrasting Soil Textures: 11-Year Field Experiments

Carbon losses from decomposition and erosion threaten intensive crop production systems. While conservation tillage enhances soil organic carbon (SOC), soil tex-ture-dependent responses and time-scales of soil quality change remain poorly understood. We addressed this gap using a dual time-scale design: 11 years of minimum tillage (MT) versus conventional ploughing (CT), followed by 5-year transitions to no-till (NT) in contrasting textures (loamy vs. silty clay) in NE Slovenia. In loamy soils, reduced tillage significantly increased SOC, dissolved organic carbon (DOC), permanganate oxidizable carbon (POX-C), particulate organic carbon (POC), and mineral-associated organic carbon (MAOC < 50 μm) in the 0-10 cm layer. In silty clay soils, high clay content provided baseline protection that masked tillage effects on bulk SOC, though POX-C and POC showed vertical stratification. MAOC in the fine fraction (< 20 μm) remained consistent (2.0-2.5%) across treatments and textures, except under CT in loamy soil (1.73%), indicating accelerated decomposition. Tillage intensity drove aggregate distribution: CT fragmented soil structure (fewer macroaggregates, higher Dm), while MT and NT promoted macroaggregate formation. Structural indices (MWD, GMD, Dm) correlated strongly with C fractions, confirming physical protection mechanisms. Our dual time-scale approach reveals labile C pools and aggregate recovery respond within 5 years of NT, while texture modulates response magnitude and detectability. Reducing tillage intensity consistently supports C preservation across textures, though lighter soils show faster, more pronounced responses.