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Competency Area 1: Basic Soil Properties

PO 3. Know the particle size fractions and size ranges.

  1. Sand, silt, and clay; coarse fragments.
    • Sand = 2.0-0.05 mm diameter particles
    • Silt = 0.05-0.002 mm diameter
    • Clay = <0.002 mm diameter
    • Coarse fragments = > 2 mm diameter
  2. Understand and use the textural triangle.

The textural triangle helps determine the soil textural classification of a soil based on its fine-earth fraction (particles <2mm, that is sand, silt and clay). On the bottom, find the percent sand, on the left hand, percent clay, and on the right hand, percent silt. As an example, a soil has 15% sand, 60% silt, and 25% clay – this soil would be classified as a silt loam (Figure from Soil Survey).


textural triangle.JPG

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