Vertical distribution of soil water repellency in ortsteinic soils in relation to land use

Abstract

Land use, soil organic carbon content and bulk density are important factors influencing the occurrence of soil water repellency (SWR) and water flow through the soil profile. This study elucidated the relations between the repellency index (RI) and contents of soil organic carbon (SOC), organic-complexed aluminium (Alp) and iron (Fep), pH, specific surface area (SSA) and bulk density in the ortstein horizon and the overlying and underlying horizons in two podzolic soils under grassland and forest. The soil under grassland was originally used as a cropland. The RI was quantified from the ethanol/water sorptivity ratio. The results showed that the RI in the ortstein horizon (20.6–27.3) in the air-dried state in both soils was many times greater than in the overlying (7.2–19.0) and underlying (6.1–11.5) horizons, whereas in moist conditions (from soil water content at sampling and air-dried state), all horizons were not repellent. The RI in the air-dried soil in the overlying horizon was higher under grassland than forest, whereas the inverse was true in both the ortstein and underlying horizons. SOC, organic-complexed Alp and Fep contents, and SSA were the highest in the ortstein horizons. The pH value increased from 5.3 in the overlying horizon to 6.0 in the underlying horizon in the grassland soil. The corresponding values in the forest soil were 4.2 and 5.0. The RI values in the dry condition were significantly correlated with Alp (R2 = 0.976), Fep (R2 = 0.798), SSA (R2 = 0.724), and SOC (R2 = 0.638). The study provides new information about the vertical distribution of soil water repellency in ortsteinic soils depending on the soil water status and the type of land use. The potential mechanisms of the distribution of SWR are discussed.