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In agricultural ecosystems, one optimized crop residue management practice, i.e., incorporating biochar produced from crop residues via pyrolysis to the soil, is considered a promising technology for mitigating climate change and improving soil quality. However, the potential mechanisms are still not well known. In this study, a five-year (2011–2015) field experiment in a Mollisol of Northeast China that included four treatments, i.e., CK (no fertilizer), NPK (mineral nitrogen, phosphorus and potassium fertilizers), NPKS (NPK plus maize straw) and NPKB (NPK plus maize straw-derived biochar), was conducted to evaluate the effects of maize straw and its derived biochar application on the following: 1) the size distribution and water stability of soil aggregates; 2) the concentrations of organic and humic carbon (C) in bulk soil and water-stable aggregate fractions; and 3) the chemical compositions of organic and humic C in water-stable aggregate fractions. Compared with the CK and NPK treatments, the proportion of macroaggregates (>0.25 mm) [mainly large macroaggregates (>2 mm)] increased whereas the proportions of microaggregates (0.25–0.053 mm) and silt + clay fractions (

Application of organic amendments, such as maize straw and its derived biochar and compost are considered as effective strategies for sustaining soil productivity. However, limited information available on the variation of soil carbon sequestration, soil quality and crop yield responses to these amendments, especially in the highly rich organic matter soils. The field experiment was conducted in a Mollisol since the fall of 2011 to evaluate the impact of chemical fertilizer plus maize residue driven materials amendments on continuous maize yield, soil carbon sequestration and soil quality parameters. The experiment consisted of five treatments: CK (no fertilizer), NPK (chemical fertilizer), NPK+ST (NPK plus maize straw), NPK+CP (NPK plus straw compost), and NPK+BR (NPK plus straw biochar). The organic materials were applied on an equal carbon input basis (3.2 Mg ha−1 per year). Soil samples were collected from 0 to 10 cm and 10–20 cm soil depths in 2017, and analyzed for contents of soil organic carbon (SOC), readily oxidizable organic carbon (ROC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), nutrients and aggregates-size distribution. The NPK+BR and NPK+CP significantly increased SOC stock at the topsoil (0–20 cm) relative to CK and NPK treatments. The amount of soil carbon sequestration (relative to SOC baseline in 2011) associated with different treatments was as follow: NPK+BR (13.1 Mg ha−1) > NPK+CP (5.60 Mg ha−1) > NPK+ST (2.90 Mg ha−1) > NPK (0.50 Mg ha−1) > CK (−1.90 Mg ha−1). However, the greatest concentrations of ROC, DOC and MBC at the topsoil were observed in NPK+CP treatment, with greater supply of available nutrients than other treatments. The NPK+BR reduced the fraction percentage of microaggregates significantly (