Soil structure development and preferential solute flow

Abstract

Soil structure and preferential flow are thought to be highly related, but quantification of this relationship has remained problematic. A combination of experiments on two soils at local and field scale was used to study the relationships between the degree of structural development, saturated conductivities Ks, moisture release, breakthrough parameters, and observations of preferential flow at the field scale. The convection dispersion equation and mobile‐immobile model were fitted to breakthrough curves, and flow channels were stained with dye. Well‐developed structure was associated with high dispersivities, a high coefficient of variation of Ks, and low mobile water contents, low exchange coefficients, and a low dyed area. Field‐scale observations matched the differences in structure and preferential flow parameters observed at the local scales. Local‐scale preferential flow appeared to highly influence field‐scale solute transport, indicating that this is an important local‐scale process which is not dampened at the field scale. A conceptual model of subsoil structural development was expanded with physical parameters matching the structural development stage to predict the likelihood of preferential flow on the basis of the saturation regime of the horizon or pedon.