A Two Domain Mesopore and Matrix Model for Cracking Soils.

The Precision Agriculture Landscape Modeling System (PALMS) is a biophysical model that uses a two-domain, mesopore and matrix, model to simulate water flow in soil.  The model was developed to utilize knowledge of the vertical distributions of the coefficient of linear extensibility and soil water content as the primary information needed to  partition porosity between the mesopore and matrix domains at any given time.  The overall goal of this project is to evaluate how effectively the mesopore and matrix model can simulate water infiltration and redistribution in soils that develop large cracks with widths well greater than those that are considered mesopores - using the same two parameters to predict the larger cracks.  In the study reported here, modeled and measured areal densities of cracks are compared.  Three soils were chosen for the comparison.  With each of the three soils, soil water content and areal density of cracks were measured with depth. The areal densities of cracks were quantified by filling them with a thin cement mixture, allowing time for it to cure, and then horizontally excavating and photographing the exposed surfaces. Estimates of the areal density of cracks from the model were compared to those measured using cement infilling and photography. Comparisons with predictions from the present form of the model and from modifications of the model were discussed.