Increased soil sodicity

Impact

Soil sodicity occurs naturally and can be increased by human activities such as irrigation.  It is caused by the presence of sodium attached to clay in the soil.  About 30% of the agricultural land in Australia has sodic soils.  Soil sodicity only becomes a problem when there is sufficient sodium attached to the clay in the soil to affect soil structure.  The sodium weakens the bonds between soil particles when the soil is wet, resulting in the clay swelling and often becoming detached.  These clay particles disperse throughout the soil water and can clog soil pores.  Under saline conditions the high sodium concentration can counter the swelling of the soil.

Suggested indicators: Soil chemistry+, Soil salinity+

Increased soil sodicity may be associated with:

Potential associated impacts Suggested indicators+ 
Soil crust formation that reduces water infiltration rate, increases runoff and reduces plant available water
  • Soil infiltration
  • Plant available water content
Increased soil waterlogging

Reduced vegetation growth and seedling emergence, resulting in:

  • reduced ground and canopy cover

Increased potential for soil erosion
  • Hillslope erosion
  • Gully erosion
  • Wind erosion

+ Descriptions of indicators (PDF, 76K)* provides a brief description of each indicator including techniques and purpose.

* Requires Adobe Reader

Last updated 7 September 2010

Land Manager's Monitoring Guide