Revealing soil‐borne hydrogel effects on soil hydraulic properties using a roughness‐triangular pore space model

Abstract

AbstractUnderstanding the influence of soil‐borne hydrogels (e.g., bacterial extracellular polymeric substances [EPS] and biofilm or root‐derived mucilage) on soil hydraulic properties is crucial for accurate modeling of flow and transport in porous media. The underlying mechanisms of how hydrogels modify soil physical and hydraulic properties, however, remain unclear. In this study, we applied a roughness‐triangular pore space model (R‐TPSM) to simulate water retention curve and hydraulic conductivity of hydrogel‐affected soils. The model considers the effective soil pore size distribution and physicochemical properties (e.g., surface tension and surface roughness) of soil and soil solution. The modeling results are in good agreement with measured water retention curves and hydraulic conductivity for different textured soils. Comparison of the fitted model parameters between control and hydrogel‐treated soil samples indicates that hydrogels reduce surface tension and shift the effective pore size distribution to a narrower size range. Hydrogels generally increase water retention in the form of adsorptive films and reduce film flow under relatively dry conditions. This study highlights the importance of considering reduced surface tension and mean pore size by hydrogels in changing soil hydraulic properties, which has important implications for accurate modeling of water distribution and flow in the rhizosphere.