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  • Soil Health

  • Physical


Soil porosity pertains to the interstitial voids existing between soil particles and aggregates, serving as conduits through which water and air can move. These voids create essential habitats for the proliferation of roots and microorganisms (Nimmo, 2004; Osman, 2013). Porosity exerts significant influence over a multitude of critical soil processes, which depend on pore dimensions, shapes, and continuity (Pagliai et al., 2004).

Management practices can alter the soil’s pore structure, leading to modifications in its physical attributes. These transformations, in turn, can have significant ramifications for long-term sustainability and soil functionality (Bodner et al., 2013; de Andrade Bonetti et al., 2017; de Oliveira et al., 2021). Total porosity has indirect links with several critical ecosystem functions, including but not limited to, biomass production, filtration, buffering, transformation of substances within the soil matrix, safeguarding the genetic diversity within the soil’s gene pool, maintenance of soil structural integrity and the regulation of soil hydrological processes (Guerra et al., 2021).

The number, activity and biodiversity of micro-organisms and earthworms are also greatest in well aerated soils and they are able to decompose and cycle organic matter and nutrients more efficiently (Soil Testing Methods Global Soil Doctors Programme, FAO).

Methodology summary

Porosity can easily be calculated if the bulk density and the particle density of the soil are known with no need for extra sampling, with the following formula: Porosity %=(1-(Bulk density)/(Particle density))×100

Particle density of mineral soils is relatively consistent and is often considered to be around 2.65 g/cm³
If particle density of organic soils is unknown, to calculate the bulk density you can use a range from 0.1 to 0.3 g/cm³

To do a visual assessment of porosity you can refer to FAO Soil Doctor guide pg. 72-73.

Metric threshold or direction of change

Thresholds are context (habitat, land use, vegetation type, soil type, etc) dependent. For example, well-drained soils with higher porosity may be suitable for grasslands, while wetland habitats might benefit from soils with lower porosity to retain more water.

Technological innovations

Electrical Resistivity Tomography (ERT) can measure how much space there is between soil particles by looking at how easily an electrical signal passes through them. The size of the particles affects this, and ERT helps us understand soil structure without digging. ERT is a promising technology for assessing soil porosity, soil structure, water movement, and overall soil health. Advances in instrumentation and data interpretation methods may further enhance its applicability. At present the accuracy of ERT results can be affected by the presence of metallic objects or infrastructure in the subsurface, which can cause distortions in the electrical signal, it has limited resolution at greater depths. ERT is time-consuming, as it requires the collection of multiple measurements along a survey line or grid, which can limit its applicability for large-scale investigations (Abd Malik et al., 2023; Azevedo & Pereira, 2023).


  • Agricultural
  • Forest
  • Grassland
  • Peatland
  • Saltmarsh
  • Wetland


  • Community


  • Low


  • Tier 1

Technical expertise

  • Medium

Standardised methodology

  • Yes