A hidden architecture

What truly matters is how soil components are arranged. Soil structure describes how sand, silt, and clay particles, along with organic matter, water, and air, are organised in space.

These components form aggregates — small clusters of particles — that create a porous structure with many interconnected spaces, known as pores. Aggregates form when soil particles are bound together by physical, chemical, and biological processes. Clay particles and organic matter act as natural binding agents. Soil organisms — plant roots, fungal threads, microorganisms, earthworms — further shape aggregates.

A useful way to visualise soil structure is to compare soil to a city: the solid particles and aggregates are like buildings, while the pores are like streets and open spaces that allow movement and exchange.