Particles are physically pushed closer together by freezing and thawing, wetting and drying, and roots pushing through the soil. At the molecular level, electrochemical charges bond clay particles together. In tropical and semitropical soils, iron oxides can cement together aggregates. Rain drops break apart soil aggregates and then fine clay particles clog the spaces between aggregates and form a crust on the soil. Organic matter management.
Regular additions feed the organisms that build soil structure.
Tillage practices . Over time, tillage increases the decomposition of soil organic matter and breaks up aggregates - especially when tillage is done in wet soil. Residue left at the surface protects surface aggregates from rain and encourages the growth of fungi that help stabilize aggregates. Compaction prevention . Compaction pushes aggregates together and eventually breaks them down.