Straw management stabilizes chemical composition of SOC and their relationship with aggregate‐associated C in rice‐rape rotation

Soil organic matter stored in soil aggregate fractions is a major soil organic carbon (SOC) stabilization process. The distribution of SOC within soil aggregate fractions and their association with SOC chemical compounds in the agroecosystem is not well understood. Our long‐term study (6 and 9 years) in central China examined the effects of tillage and straw management practices on chemical functional components of SOC, SOC contents of soil aggregates, and the relationship of the SOC composition with aggregate‐associated C in a rice‐rape cropping system. The soil samples from 2 sites were separated into six aggregate classes (>5, 5–2, 2–1, 1–0.5, 0.5–0.25, and 5 mm, 5–2 mm, 2–1 mm aggregates and 5–10% was stored in other aggregate fractions (1–0.5 mm, 0.5–0.25 mm and <0.25 mm) after straw return. SOC Chemical components were positively and negatively correlated with aggregate‐associated C fractions. This study concluded that straw management improved the chemical composition of SOC and increased the SOC contents of bulk soil as well as helped store more organic matter in macroaggregates.