A modified model for estimating the full description of soil particle size distribution

Abstract

A modified model for estimating the full description of soil particle size distribution. Can. J. Soil Sci. 93: 65Á72. A full description of the particle size distribution (PSD) curve is widely used as a basis for estimating soil hydraulic properties. However, the incomplete experimental data of PSD sets (i.e., percent clay, silt, and sand) often limit its uses. In this study, an empirical model modified from the Weibull model was used to estimate the complete description PSD from clay, silt and sand fractions. Results show that the estimated distribution agrees reasonably well with the actual distribution for 168 soils samples studied within six different textures. The values of coefficients of determination, the average absolute deviation and the maximum absolute deviation were 98.6%, 3.3% and 12.6%, respectively. The modified model performed best for silt loam samples containing about 70% silt content. The estimation accuracy varied with radii interval. For the estimated PSD curve, a 0.05Á0.1 mm size interval was most poorly estimated and had the maximum deviation (28.2%), while the 0.5Á1 mm interval was estimated well by the modified model. The model is recommended to estimate complete soil PSD using only clay, silt and sand fractions, which can be well fitted by the Weibull model. Further studies are suggested to validate the PSD estimation by this model when applied to soils with greater variation in texture.