Estimating soil particle-size distribution for Sicilian soils

The soil particle-size distribution (PSD) is commonly used for soil classification and for estimating soil behavior. An accurate mathematical representation of PSD is required to estimate soil hydraulic properties and to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of three PSD models (LN2D, HPD and FD3) to fit 243 measured PSDs from a wide range of soil textures in Sicily and to test the effect of the number of measured particle diameters on the fitting of the theoretical PSD. The worst fitting performance, established using three statistical indices (MXE, ME, RMSE), was obtained for the LN2D whereas the HPD and FD3 distributions yielded relatively similar fitting performances. However, for each textural class the best performance to the measured PSD was detected for the FD3 model. Decreasing the number of measured data pairs from 14 to eight determined a worse fitting of the theoretical distribution to the measured one. It was concluded that the FD3 has a wide applicability for Sicilian soils and that the comparison of different PSD investigations can be affected by the number of data pairs measured by the investigators.