soil management: A good soil management, proper tillage with a good crop rotation system maintains the soil in a good state of aggregation.
Adsorbed cations: Na+ and K+ ions disperse the soil, while Ca2+, Ba2+ have favorable effects on the aggregation.
Micro-Organisms: Filamentous fungi and microbial decomposition products of O.M. have a binding effect on soil particles, burrowing activities of insects, excrements of earthworms change the soil structure.
Variation of soil moisture: Drying of soil forms cracks and big clods. Poorly drained soils have unfavorable structure.
Influence of O.M. : Binding effect, water-holding capacity, porosity are increased by adding O.M. to the soil. Cementing action of humus is equivalent to certain inorganic compounds like oxides of Fe which provide most of the long term aggregate stability.
the only practical way to improve the soil structure is to add O.M to the soil.