Effects of soil morphology on hydraulic properties: I. Quantification of soil morphology

Utilization of existing soil survey databases for characterizing water flow and solute transport in field soils has practical value. However, the lack of a proper means for quantifying soil morphology limits the incorporation of soil structural information into models. In this study, we examined basic relationships between five major soil morphological features (texture, initial moisture, pedality, macroporosity, and root density) and steady infiltration rates for 96 soil horizons of varying structure. Based on these relationships, a point scale system was developed as an approach to quantify soil morphology. Descriptive morphological classes were first rated with respect to their potential impacts on soil water flow rate. Points that provided the best correlation with the measured steady infiltration rates were then obtained for each morphological class through a computer optimization program. The optimal points assigned to each morphological feature were divided by the maximum value to yield a morphometric index of 0 to 1. Such an approach permitted the determination of interrelationships among different morphological features that would otherwise be difficult with qualitative descriptors. The proposed morphology quantification system also has potential in facilitating pedotransfer studies of estimating water flow and chemical transport parameters from soil survey databases including structural descriptors.