Since several years the fractal fragmentation model has attracted the attention of researchers, as a logic way to describe and interprete observed particle size distributions. Textural analysis has shown to be very important because of its usefulness in the dignosis and inferences about soil functioning and use. Most popular methods of textural analysis employ sedimentation of particles in water using the hydrometer or the pipet. Both have the objective of determining the particle fraction remaining in suspension at predetermined time and to relate them with particle diameters. In the present work a new power law relationship between the mass fraction in suspension and the time was developed. Using this relationship it was possible to determine the fragmentation fractal dimension of a set of particles in sedimentation. The new equation has been checked with data obtained in this research by the Bouyoucos's hydrometer, and others published in the literature, using the Robinson's pipet method. The agreement between the model and the experimental data, using non linear regression, was excellent. Resulting fractal fragmentation dimensions ranged from 2.404 to 2.512, for samples from La Plata, Argentina, and between 2.434 and 2.819 for soils from California, USA. Determination coefficients, R², were always higher than 0.9.
soils; texture; fragmentation
