Stabilization of soil aggregate and organic matter under the application of three organic resources and biochar-based compound fertilizer

Purpose Biochar mediation of soil structure and carbon (C) sequestration has been tested, but the underlying mechanisms in this process are poorly understood. We investigated the effects of different organic matter applications on soil aggregation and associated C in Northeast China. Materials and methods Non-disrupted soil samples (0–20 cm in depth) were collected from the field improvement experiment (established in 2009) with four addition treatments: (1) corn straw (CS), (2) pig manure compost (PMC), (3) biochar from corncob (BIO), and (4) biochar-based compound fertilizer (BF), of which CS, PMC, and BIO were combined with extra mineral fertilizers including nitrogen (N), phosphorus (P), and potassium (K). Soil aggregate distribution and associated C concentrations were estimated using physical fractionation techniques. Results and discussion The CS and PMC additions increased mean weight diameter (MWD), large macroaggregate fractions (>2 mm), and small macroaggregate fractions (0.25–2 mm). In contrast, BIO and BF significantly increased silt + clay fractions (