Effects of long-term different fertilization on soil aggregates and organic carbon fractions on sloping upland of purple soil

Long-term fertilization has a significant impact on soil organic carbon (SOC) stock. However, fertilization impact on physical fractions of SOC is still poorly understood on sloping upland of purple soil in the central Sichuan Basin, southwestern China. Therefore, this study assessed the impact of long-term different fertilization on soil aggregates distribution and its organic carbon factions under an intensive wheat (Triticum Aestivium L.)-maize (Zea mays L.) cropping system through four fertilization treatments, no fertilizer (CK), applied mineral fertilizer (NPK), pig manure matched with mineral fertilizer (OMNPK), and crop straw residue matched with mineral fertilizer (RSDNPK). Soil samples from 0~20 cm soil layer were separated into four soil aggregations (>2 mm large macroaggregates-LM, 0.25~2 mm small macroaggregates-SM,