Abstract
Soil water repellency (SWR) is a major problem across the globe and often occurs in sandy soils. SWR inhibits seed germination in crops and pastures, enhances surface runoff and erosion, and accelerates the movement of nutrients and pesticides into groundwater. SWR is caused by the accumulation of hydrophobic organic compounds released from plants and soil microbiota, and in some studies the severity of SWR has been related to soil organic carbon (OC) contents and the presence of particular organic compounds. In addition, factors such as root exudates, contributions from multiple plants, compounds produced during the decomposition of organic matter, and fungal bio-products influence SWR. SWR is also related to soil physical properties such as surface area and chemical properties such as pH. In general, SWR increases with increasing soil OC and decreases with increasing soil surface area; therefore sandy soils are more prone to SWR; however if a soil contains sufficient OC, it will be repellent. This review explores the linkage between SWR and physicochemical properties of soils and suggests research directions to uncover the interplay of the various contributing factors to SWR.