Soil structure | Soil Science 

Terms: physical properties: structure, macropore, micropore, aggregate
Whereas soil texture describes the particle sizes of soil and their relative proportions, soil structure explains how the individual particles are organized into larger structures called aggregates.
A soil aggregate often takes on one of a few forms: spherical, flat, blocky, and columnar or prism-shaped. They can be formed by physical processes, chemical interactions, or as a result of biological activity - e.g. earthworm, termite excrement; biological “glues” or exudates from plants, bacteria and roots. Organic matter is very helpful in creating aggregates.
Because the aggregates are larger than individual particles, there are larger pore spaces between them - these are called macropores and are important for water, air and roots. Inside an aggregate however you will still have smaller pores between the particles, which are called micropores. The micropores are important for holding water for plant use, since water drains out of the larger macropores soon after irrigation or rain.
Soil structure is delicate and easily damaged by a variety of human activities. It’s best to buffer the soil using a thick layer of wood chips that also continuously contributes organic matter to the soil.
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