Particle-size distribution

Soil texture

Important parameter for the characterisation of soils

Based on the particle-size distribution a soil can be assigned to a distinct soil texture. This procedure considers only the fine soil which comprises all particles with an equivalent diameter smaller than 2 mm (= 2000 µm). Soil constituents bigger than 2 mm are referred to as soil skeleton or coarse soil. The fine soil is composed of different particle-size fractions, i.e., sand (S), silt (U) and clay (T) which - according to the German particle-size classification - include the following particle sizes:

  • Sand: 2000 - 63 µm
  • Silt: 63 - 2 µm
  • Clay: < 2 µm

Under natural conditions these particle-size fractions mostly occur as mixtures and only rarely in their pure form. The ratio of the size fractions to one another determines the soil texture and the properties of the soil. The mixtures can be described by frequency distributions and summation diagrams.

The predominant particle-size fraction is name-giving, e.g. loamy-sand means a sandy soil containing a smaller loam fraction. The term 'loam' refers to a soil containing more or less equal fractions of sand, silt and clay.

As one of the most conservative soil features the particle-size distribution is an especially useful and meaningful parameter.

The particle-size distribution is also determined in suspended particulate matter (SPM) and in sediments.

Substances

  • Sand
    Particle-size fraction with an equivalent diameter of 2000 - 63 µm
  • Silt
    Particle-size fraction with an equivalent diameter of 63 - 2 µm
  • Clay
    Particle-size fraction with an equivalent diameter < 2 µm

Specimen

  • Fine insoluble mineral or organic particles in the water phase
  • Soil is livelihood and biosphere for humans, animals, plants and soil organisms. All the substances brought in are transported, transformed and/or accumulated in the soil.

Sampling area

Sampling period

2002 - 2018