Aggregates are a basic unit of soil structure. Maintenance of soil structure is key to sustainable agroecosytems. Good soil structure promotes favorable water relations and rooting environment for plants. Well-structured soils build up organic matter and are less susceptible to erosion.
Organic materials are the main stabilizers of soil aggregates .
Microbes contribute much of that by their activity in decomposing plant, animal, and microbial remains , by their own biomass, and by the products they form while decomposing organic residues. As you will see further in this website, bacteria tend to stabilize smaller particles, while fungi bind together larger particles and enmesh soil particles and small aggregates into larger aggregates.