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

Classification of soil texture is usually carried out by considering differ ent textural classes which group together soils with mass percentages of cl ay, silt and sand within certain ranges. Soil samples of diverse compositio n, however, become indistinguishable from each other under the grouping tha t these classes establish. A parametrization of soil texture based on the e ntropy dimension is proposed. Following Martin & Taguas, a fractal modellin g allows us to compute the entropy dimension of the modelled particle-size distribution (PSD) from readily available textural data. First, the role an d 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 en tropy dimension for a large number of soils from the Soil Conservation Serv ice (SCS). Soil textural classes can be characterized by the average value of the entropy dimension of soils belonging to each class. Soils with entro py dimensions between prescribed limits are located within a well-defined r egion of the textural triangle. Thus, entropy dimension, via the fractal mo del of Martin & Taguas, provides a continuous parameter which is suitable f or a fine quantitative characterization of soil textures using conventional textural data.