Relationships of soil properties to water repellency and the effectiveness of clay ameliorants

[Truncated] Water repellency affects about 5 million hectares of agricultural land across southern areas of Australia and causes large losses of production. In order to predict the occurrence of water repellency, which is a labile property, from field survey data obtained throughout the year, it is necessary to identify predictive relationships between water repellency and commonly measured soil properties. Also claying is becoming a widely accepted practice for treating water repellent soils and hence it is important to determine the most appropriate clay materials to treat water repellency.

Relationships between water repellency and soil properties were evaluated for diverse soil assemblages that include a set of reference soils from the south-west of Western Australia (an area of 250 000 km²), a set of farm soils from the south-west of Western Australia and more intensively sampled suites of soils in several smaller soil/landscape associations within the south-west of Western Australia (≅1000 km²), soils from single farms (1-10 km² ) and transects (≅0.001 km²) and single soil profiles(≅m²). The severity of water repellency was assessed by measuring water drop penetration time (WDPT) in seconds and related to intrinsic properties of soils using log transformed data.