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

Soil texture-dependent responses and time-scales of soil quality change, especially soil carbon, remain poorly understood. We addressed this gap using a dual time-scale design of long-term field experiments: 11 years of minimum (MT) versus ploughing tillage (CT), both followed by 5-year transitions to no-till (NT) in contrasting textures (loamy vs. silty clay) in NE Slovenia. In loamy soils, reduced tillage in the 0–10 cm layer increased soil organic carbon by 40–48%, dissolved organic carbon by 36–64%, permanganate oxidizable carbon by 67–84%, particulate organic carbon by 76–95%, and mineral-associated organic carbon (MAOC < 50 μm) by 28–34%. In silty clay soils, high clay content masked tillage effects, though labile pools showed stratification. MAOC < 20 μm remained stable across treatments and textures (2.0–2.5%), except under CT in loamy soil (1.73%), indicating enhanced decomposition. In loamy soils CT increased by 0.5–1 and 1–2 mm and decreased >20 mm and in silty clay soils increased <0.5, 1–2 and 2–4 mm aggregate formations. The MWD, GMD, Dm indices 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.