macroporosity

Macroporosity refers to the portion of a porous material’s pore space that consists of large, interconnected voids. These macropores are typically tens to hundreds of micrometers in diameter or larger and allow rapid movement of water and air through the material, in contrast to smaller pores that hold water by capillary forces and restrict flow.

In soils, macroporosity is strongly influenced by structure and biology. Pore networks form through soil aggregation, root channels, and bioturbation by earthworms and other organisms. Macropores dominate rapid infiltration and drainage, facilitate gas exchange, and promote deep rooting. They are, however, vulnerable to compaction and disturbance, which can collapse channels and reduce drainage.

Measurement and analysis: Macroporosity is often assessed by infiltration rate tests, dye-tracing, or image-based approaches. Direct methods include double-ring infiltrometry and measurements of saturated hydraulic conductivity that reflect large pores. Non-destructive imaging techniques, such as X-ray computed tomography, can quantify pore-size distributions and connectivity in three dimensions, although access may be limited to small samples. Macroporosity is distinct from microporosity and mesoporosity, which involve smaller, less connected pores associated with water retention and surface area.

Applications and relevance: In agriculture and hydrology, macroporosity controls infiltration, drainage, drought resilience, and root growth. In geological materials, including fractured rock, stones, ceramics, and concrete, macropores govern fluid flow, weathering, and durability. Preservation or enhancement of macroporosity is a consideration in soil and material management as well as in the design of engineered porous media.