An entropy–based parametrization of soil texture via fractal modelling of particle–size distribution

Classification of soil texture is usually carried out by considering different textural classes which group together soils with mass percentages of clay, silt and sand within certain ranges. Soil samples of diverse composition, however, become indistinguishable from each other under the grouping that these classes establish. A parametrization of soil texture based on the entropy dimension is proposed. Following Martín & Taguas, a fractal modelling allows us to compute the entropy dimension of the modelled particle–size distribution (PSD) from readily available textural data. First, the role and meaning of the entropy dimension computed in that manner for soil PSD is discussed. Then the fractal model is applied to compute the value of the entropy dimension for a large number of soils from the Soil Conservation Service (SCS). Soil textural classes can be characterized by the average value of the entropy dimension of soils belonging to each class. Soils with entropy dimensions between prescribed limits are located within a well–defined region of the textural triangle. Thus, entropy dimension, via the fractal model of Martín & Taguas, provides a continuous parameter which is suitable for a fine quantitative characterization of soil textures using conventional textural data.