Extent of water repellence

Soil water repellence is the resistance of soils to wetting, sometimes to the extent that they remain dry even after significant rainfall events or irrigation.

Most of the soils (including in coastal and forest areas) in the South West NRM region are severely water repellent affecting agriculture production.

This is a key issue affecting agriculture across Australia, and is also an issue that can be managed. Nearly 3.3 million hectares of agricultural soils across the south-west of WA are at high risk of water repellence and a further 6.8 million hectares are at moderate risk. The cost of water repellence resulting in reduced production is estimated at $251 million per year.

The consequences of water repellence are:

  • poor crop and pasture establishment
  • increased risk of wind and water erosion
  • poor water and nutrient use.

The extent and severity of water repellence appears to be increasing as cropping increases together with early sowing, minimum tillage and reduced break of season rainfall.

While limited data are available for assessing current condition and tracking trends in water repellence, there are a several sources of evidence to determine if the extent of the hazard shown by the hazard map is realised in practice. Most of the soils (including in coastal and forest areas) in the South West NRM region are severely water repellent affecting agriculture production.

  • Coastal areas: Most of the aeolian (wind deposited) sandy areas are severely water repellent. No problems where alluvial soils occur.
  • Forest soils now in crop (previously pastures) have severe water repellence problems. The higher rainfall western portion of the zone has water repellence in sandy gravelly areas.

Data Source:

  • Department of Agriculture and Food, 2013.  Report card on sustainable natural resource use in agriculture: Status and trends in the agricultural areas of the south west of Western Australia. Department of Agriculture and Food, Western Australia. 188 pages.