DESCRIPTION OF SOIL PORE-SIZE DISTRIBUTION WITH MEAN WEIGHTED PORE DIAMETER AND COEFFICIENT OF UNIFORMITY

Mean weighted pore diameter and coefficient of uniformity concepts are introduced to describe the soil pore size distribution using only soil moisture characteristic data. Mean weighted pore diameter gives the mean pore size and coefficient of uniformity details the heterogeneity of the pore size distribution. Representing soil water characteristic information with single variables allows this information to be easily included in statistical analysis and readily interpreted with respect to other agronomic factors. The cummulative percentage of pore volume versus pore diameter (calculated from pore water tension) is plotted, an equation fitted to the curve, and the area above it integrated, resulting in an areal determination from which the mean weighted pore diameter is calculated. From the same plot, the pore diameter of the 75th and 25th percentiles are determined, and the coefficient of uniformity equals their ratio; it is ranked on an indexed scale to assess the degree of pore size heterogeneity. Different boundaries may be defined for the pore size range under consideration to allow one to investigate specific changes in macro-, meso-, or micropores. Examples are shown for a typic Paleudult and a typic Hapludult.