Soil Science

Particle sizes

diagram comparing particle sizes
In Australia, we utilize the International system to classify particle sizes, which are as follows:

  • Clay (< 2 μm equivalent diameter)
  • Silt (2-20 μm)
  • Fine sand (20-200 μm)
  • Coarse sand (0.2-2 mm)

To illustrate the magnitude of these sizes, if the smallest clay particle were the size of a flea, comparatively, the largest sand particle would be the size of a small office building.

Soil texture classification is based on the fine earth fraction (< 2mm), while the amount of gravel (> 2mm) may also be recorded. Soil chemical analyses are typically conducted on the fine earth fraction.

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