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Soil Structure

  • Soil Health

  • Physical

Summary

Soil structure refers to the arrangement of soil particles into distinct geometric patterns (Dexter, 1988). Soil structure, in conjunction with soil texture, collectively governs parameters such as total porosity, pore size and distribution, thereby influencing the retention and movement of water within the soil matrix. The complexity of soil structure arises from a confluence of diverse factors, including environmental conditions, soil management practices, mineral composition, textural attributes, the presence of soil organic matter, pedogenic (soil-forming) processes, microbial activity, and the prevailing moisture regime (Bronick & Lal, 2005; Osman, 2013; Pagliai et al., 2004).

Soil structure has the capacity to serve as an indicator of ecosystem structure or habitat extent (Guerra et al., 2021).

Methodology summary

Soil structure can be measured through Visual Evaluation of Soil Structure (VESS):

  • Dig out one spade-sized block of soil (depth approximately 30 cm)
  • Cut down on three sides and then lever the block out, leaving one side undisturbed
  • If the soil block falls apart easily, dig out one block and then a second next to it to assess
  • Lay the soil block on a plastic sheet or tray
  • If the structure is uniform, assess the block as a whole
  • If there are two or more horizontal layers of differing structure, identify the layer with the poorest structure (the limiting layer)
  • Record the depth of this limiting layer and carry out the rest of the assessment on this layer
  • Assign a score following instructions on the below leaflet from AHDB

A detailed guide on visual evaluation of soil structure on site can be found at the AHDB website https://ahdb.org.uk/knowledge-library/how-to-assess-soil-structure

Metric threshold or direction of change

Score can be good moderate and poor.

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).

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

Scale

  • Community

Cost

  • Low

Tier

  • Tier 1

Technical expertise

  • Low

Standardised methodology

  • Yes