A geometric equation for representing morphological field information in horizons with compound structure

Recent advances in the quantification of ped geometry have revealed a need to integrate the values obtained from individual peds within horizons that contain multiple ped sizes, grades, and/or types. Here we propose a general equation to represent with a single value the structural character of a horizon that may contain single, multiple, and/or compound structure. The equation is based on the calculation of a weighting parameter from estimates of the vertical cross-sectional area of each unique structure class present in a horizon. The equation can be used to integrate quantifiable aspects of either structure size, grade, or shape. We demonstrate the usefulness of this equation in two soils—the Alloway series (Aquic Paleudults) and Holdredge series (Typic Argiustolls)—that exhibit multiple or compound structure in each horizon. This work may extend the applicability of structural information from previously described soils, enhance existing profile development indices, and aid the formulations of mechanistic soil hydrological models that account for the depth distributions of soil structural properties.