Variation of the hydraulic properties and solute transport mechanisms in a silty-clay soil amended with natural zeolites

• Soil column amended with zeolites shows higher volumetric water content and storage.
• Numerical modeling assesses the changes in physical soil properties induced by zeolites.
• Natural zeolite amendment can limit water and solute losses from soils.

This study aims to quantify changes in flow and transport parameters induced by the addition of zeolites in a silty-clay soil. Hydraulic and physical processes governing solute transport under variably saturated flow conditions were studied in a laboratory scale analog model (AM) irrigated with canal water for seven weeks. One plot of the AM was fertilized with 270 kg-N/ha of urea while the other plot was amended with 5 kg/m2 of NH4+-enriched chabazite. The observed water flow was inversely simulated using the single porosity (SP) and the dual porosity (DP) approaches; solute transport was inversely simulated using the convection–dispersion equation (CDE) and the mobile–immobile (MIM) approaches using HYDRUS-1D. Total domain reflectometry (TDR) probes were used to track soil water content and salinity while moisture sensors allowed obtaining the matric potential. The transport of bulk solutes through the soil could be coherently described using a simple approach (SP + CDE). Inverse parameter estimation suggested that percolation and solute front can be confidently predicted in silty-clay soils in case of low precipitation intensity using a combination of TDR and matric potential monitoring techniques. This study shows that NH4+-enriched zeolites increase the water retention capacity even in silty-clay soils, thus limiting water and solute losses.