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DATA · GLOSSARY · SUBSTRATE PROPERTIES

What is air-filled porosity (AFP)?

Coir glossary · Updated 2026-09-22 · Also in Português →

Volume of air remaining in the substrate after gravitational drainage, expressed as a percentage of total container volume. AFP is critical for root respiration; insufficient air causes root suffocation and disease. Coir pith: 10–30% AFP depending on particle size. Peat moss: 5–15%. Blending coir chips with pith increases AFP.

Air-filled porosity (AFP): equivalents.

PT: porosidade de aeramento · ES: porosidad de aireación

Source: Blok/WUR · EN 13041. Definition from the Carve coir glossary, where the full source list is given.

Related terms.

Bulk density: Mass of substrate per unit volume, measured on a dry basis. Unit: kg/m³ or g/L. Coir pith bulk density: 40–90 kg/m³.

Cation exchange capacity (CEC): Measure of a substrate’s ability to hold and exchange positively charged nutrient ions such as Ca2+, Mg2+, K+ and Na+.

See also: Coir pith from Brazil: specification checklist · back to the coir glossary.

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About this page. Part of the coir glossary maintained by Carve Biorrefinaria Agroindustrial Ltda, a coir pith and fiber producer in Paraipaba, Ceará, Brazil. Corrections: [email protected].