Tillage effects on residue-derived carbon distribution among soil fractions in a Mollisol

•Different modes of residue return lead to the same enrichment of RDC in plough layer.•Tillage had no effects on RDC distribution in labile and recalcitrant fractions.•No-tillage provided strong protection for newly derived carbon via macroaggregate.•RDC could reach 10–20 cm in no-tillage through leaching and stored in MAOC. The soil organic carbon (SOC) cycle is dynamic and exhibits both addition of new carbon and consumption of existing SOC; carbon inventory in the soil is the net result of these two opposing processes. Quantifying the residue-derived carbon (RDC) under different tillage systems via 13C tracing technique provides an objective appraisal of the contribution of returned residue to soil carbon sequestration in bulk soil and different fractions. We used 13C-labelled maize residue to monitor the fate of RDC stock (RDCstock) in different soil fractions under no-tillage (NT) and mouldboard ploughing (MP). Accumulation of RDC increased in the surface layer under NT while it decreased in all layers under MP over time. After two years, both NT and MP stored an equivalent amount of RDCstock with a RDCconversion rate of 16.8–17.0 %. Tillage had no effect on the RDC concentration (RDCcon) in microaggregate (Mic), silt–clay (Si-Cl), labile organic carbon (LP-C) and recalcitrant carbon (RP-C), but affected the RDCcon in macroaggregate (Mac) and particulate organic carbon (POC). NT generated more RDCstock in Mac than MP, which was induced by the higher RDCstock in coarse particulate organic matter (cPOM) and occluded silt–clay (O-Si-Cl). The percentage of RDCstock in mineral-associated organic carbon (MAOC) contributed more to total RDCstock than POC in both NT and MP, but RDCstock in POC was higher in NT (47 %) than MP (18 %). Most (70 %-75 %) of RDCstock existed as LP-C in both tillage practices. Our results showed that although the total RDCstock reached the same status in both NT and MP, the distribution in soil fractions varied, especially in physical fractions. RDC reached 10–20 cm in NT through leaching and was stored in MAOC, and NT provided strong protection for newly derived carbon via macroaggregates. It also inferred that tillage practices strongly affected the way that newly derived carbon was stored.