A Unifying Quantitative Analysis of Soil Texture: Improvement of Precision and Extension of Scale
- Mostafa A. Shirazi ,
- J. Warren Hart and
- Larry Boersma
This paper extends a procedure for transforming the standard textural triangle into a new diagram based on mean particle size, dg, and standard deviations of particle size, σg. Values of dg and σg, obtained from the mechanical analysis on percents of clay, silt, and sand, provide a unified basis for comparing soils and physical and chemical properties of the soils. It is shown that the procedure proposed earlier is valid for samples that do not have a lognormal distribution for the whole sample. Using this approach, samples with very different distributions of each fraction can be accurately described. Information from different classification systems (e.g., USDA, ISSS, and engineering) can be used to calculate dg and σg, thus making it possible to unify the systems. The procedure further makes it possible to extend the scale to include particles with diameters > 2 mm. Mean particle size and standard deviates are correlated with soil properties. An application is shown in the from of a relationship between water retention and dg and σg.
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