2025 journal article
Modeling compaction effects on soil water retention across the full moisture range: Calibration and validation
VADOSE ZONE JOURNAL, 24(1).
open access via doi.org (publisher)Abstract Soil compaction leads to an increase in bulk density () and results in a shift in pore‐size distribution toward smaller pores. These changes alter the soil hydraulic properties (SHPs), that is, the water retention curve and the hydraulic conductivity curve. Most existing models that address the impact of changes in on SHP have been confined to SHP models that consider only capillary water, neglecting water stored and transmitted within adsorbed films (noncapillary water). Recently, a new prediction model was developed that combines the Peters–Durner–Iden (PDI) SHP model system, which accounts for capillary and noncapillary water, with a prediction scheme for compaction effects. However, this new approach has yet to be calibrated and tested against data from soils with varying textures. The objective of this study was to calibrate and evaluate the new water retention model using a comprehensive dataset from the literature. Two different variants, which vary in the number of degrees of freedom have been tested. Remarkably, the variant with only one adjustable parameter, the one that shifts the pore‐size distribution by scaling the pressure head, was sufficient to accurately describe the data. All other parameters can either be fixed at the reference value or scaled based on straightforward physical reasoning. The model achieved low calibration errors (median root mean square error [RMSE]: 0.013; median mean error [ME]: 0.0014) and performed satisfactorily in validation (median RMSE: 0.025; median ME: −0.014). Based on our results, we hypothesize that the scaling approach is independent of the capillary saturation function and that this method might be applied to other models within the PDI system without new calibration.