Organic amendments and gypsum reduce dispersion and increase aggregation of two sodic Vertisols

•Organic amendments and gypsum effected soil dispersion and aggregation.•Gypsum can reduce dispersion but has no effect on mean weight diameter.•Lucerne increases large macro aggregates but cannot control dispersion.•Aryl C and O-aryl C functional groups can control dispersion in the sodic soils.•Not all organic amendments can control soil dispersion and aggregation equally.