Aggregation: Physical Aspects

A soil aggregate is “a group of primary soil particles that cohere to each other more strongly than to other surrounding particles.” Soil aggregates form through the combined action of aggregation and fragmentation processes. That is, attractive and disruptive forces act on the particles in the soil to cause greater cohesion among some particles, and groups of particles, than others. Most soils break up naturally into some form of aggregates, as pictured in Figure 1. Important physical aspects of aggregates include their size, density, stability, structure, and their effect on the transport of fluids, solutes, colloids, and heat.