Particle-Size Distribution (PSD)
Definition
The proportion by mass of soil particles falling within each size fraction. Expressed as a curve or a table of percentages, and the central analytical output of particle-size analysis.
- Basis
- Proportion by mass per size fraction
- Output
- Curve or table of percentages
- Role
- Central output of particle-size analysis
Common questions
How is particle-size distribution typically reported?+
As a cumulative curve plotting percentage passing against particle diameter, or as a table breaking down the percentage by mass in each size fraction.
Why is mass used rather than particle count?+
Mass better reflects the practical composition of a soil sample and is what sieving and sedimentation methods directly measure, rather than requiring individual particles to be counted.
Related terms
- Hydrometer Method
- A sedimentation technique that uses Stokes' Law to determine the proportion of silt and clay from the rate at which particles settle...
- Laser Diffraction
- An instrumental method where a dispersed sample passes through a laser beam and the angular diffraction pattern is inverted to produce a...
- Ribbon Test
- A field method for estimating texture by wetting a small amount of soil and extruding it between thumb and finger. The length...
- Sieve Analysis
- Mechanical separation of soil particles by passing a dried, dispersed sample through a stack of sieves with calibrated apertures from 2 mm...
- Textural Triangle
- A ternary diagram with sand, silt, and clay at the three apices. A point plotted from the measured percentages of those three...