Performance and modeling of infiltration flow in cracked saline soils

Increasing soil salinization and cracking pose threats to agricultural productivity worldwide and can lead to long-term adverse consequences on soil hydrology. However, the combined effects of salts and cracks on water–salt migration and distribution remain unclarified. Furthermore, a numerical approach for modeling infiltration flow in cracked saline soils has not been developed. Therefore, we aimed to investigate the effects of salinity, crack angle, and crack depth on water and salt flows during the infiltration process. By integrating Richards’ equation, the convection–dispersion equation, and cubic law, a two-dimensional numerical approach was proposed and a model based on finite-element theory was established to simulate the infiltration process and soil water and salt distribution in cracked soils. The experimental observations indicated that soil salts and cracks had profound effects on the infiltration process. Specifically, higher soil salinity reduced cumulative infiltration, whereas larger crack angles and smaller crack depths increased it. However, differences in salinity did not significantly affect wetting pattern morphology. Conversely, differences in crack patterns caused differences in wetting pattern morphology, but the differences in the morphological characteristics gradually diminished when the crack depth exceeded 5 cm. After infiltration, the final average soil moisture showed a tendency to decrease with an increase in soil salinity and decrease in crack angle, and changes in the crack depth caused marked changes in the soil water distribution. Additionally, large crack angles and small crack depths facilitated salt leaching. The proposed model was employed and validated through comparisons between experimental observations and numerical simulations, which showed its high accuracy in simulating the infiltration process and water and salt distribution in cracked saline soils, with R² values of 0.996–0.999, 0.985–0.999, 0.257–0.999, and 0.985–0.999 for cumulative infiltration, wetting pattern morphology, and distribution of water and salts, respectively, in all treatments. Our findings elucidate the influence of soil salts and cracks on water flow and confirm the potential of using simulation to predict water infiltration in cracked saline soils.