Addition of Fine Sand in the Low‐Permeability Dryland Saline‐Sodic Soil Increases the Permeability and Soil Moisture Conservation

ABSTRACT Soil salinization poses a significant challenge to farmland tillage and production worldwide, especially in the dryland saline‐sodic soils area characterized by clayey texture, low permeability, and high compaction. How to solve soil water infiltration of the low‐permeability saline‐sodic soils is an important practical problem that has been restricting its agricultural production availability. In this study, fine sand with particle sizes of 0.15–0.50 mm was used for two treatments: covering soil with a 0.5 cm thick layer and mixing at a 1:2 ratio (fine sand: saline‐sodic soil) to evaluate sand addition effects on soil physical and hydraulic properties. Results showed that the addition of fine sand to the low‐permeability soil significantly improved the soil physical properties. Mixing fine sand into low‐permeability soil reduced bulk density ( BD ) and soil compressive strength ( SCS ) of surface soil by 2.8% and 41.5%, while increasing total porosity ( TP ), non‐capillary porosity ( NCP ) and soil water content ( SWC ) by 3.0%, 11.3%, and 26.6%, respectively. Additionally, fine sand covering onto the low‐permeability dryland soils led to a significant decrease in SCS , TP , and NCP by 30.1%, 4.6%, and 20.3%, respectively, while SWC increased by 81%. Soil infiltration rate was increased due to mixing fine sand into the soil. The initial infiltration rate (IIR) and steady‐state infiltration rate (SIR) significantly increased by 65.1% and 44.5% after mixing fine sand into the soil, respectively. BD and NCP were the dominant influence factors on SIR, and SCS and NCP were identified as the main influence factors on IIR when employing fine sand covering and mixing for the low‐permeability soils. Therefore, this study's findings highlighted the effectiveness of the addition of fine sand in improving soil permeability and soil water conservation and provided a tested practical basis for the addition of fine sand to enhance the sustainability of the saline‐sodic soils.