Effect of water salinity and sodicity on soil least limiting water range

Abstract

This study aimed to evaluate the effects of water salinity and sodicity on the least limiting water range (LLWR) of two clay loam and sandy loam soils. The undisturbed soil samples were subjected to different water qualities, including three levels of sodium adsorption ratio (SAR, 1, 5, and 12) and electrical conductivity (EC, 1, 6, and 10 dS m⁻¹). Our findings indicate that increasing EC at each SAR led to greater soil water retention. This was attributed to salinity affecting pore size distribution toward smaller pores by altering the diffuse double layer and causing soil particle flocculation. With increasing SAR levels at each EC level, soil water content at the wilting point also rose due to structural changes, clay swelling, and dispersion, resulting in more micropores and increased adsorptive surfaces in the soil. Additionally, soil volumetric water content at a 10% air-filled porosity decreased, while values at a critical penetration resistance of 2 MPa increased with higher bulk density across all treatments. The LLWR showed a negative correlation with bulk density in clay loam soil across all SAR and EC treatments. The LLWR increased with higher water EC but decreased with increasing water SAR. The highest LLWR was observed at SAR = 1 and EC = 10 dS m⁻¹, while the lowest occurred at SAR = 12 and EC = 1 dS m⁻¹. The results revealed that elevated values of SAR in irrigation water reduced soil water accessibility for plants. However, as irrigation water salinity increased, the detrimental effects of SAR diminished.