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TOPLINE PLANT COMPANY THE HOME OF EYRES GREEN SALTBUSH HOME WHO WE ARE SALINITY HOW IT BEGAN NATIVE SALTBUSH EYRES GREEN INFORMATION FEED ANALYSIS REPORT NEWS ARTICLE CONTACTS LANDCARE AWARD PLANT BREEDERS CERTIFICATE TESTIMONIALS
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What is salinity?
Salinity refers to the presence of soluble salts in the soil and water, including surface water
and groundwater. The salt can be in many forms including sodium chloride, calcium, magnesium,
carbonate, bicarbonate and sulphate.
Some soils and landscapes are saline in their natural state, for example inland salt lakes and
soils formed from saline parent materials. This is called natural or primary salinity.
Secondary salinity is due to human activities such as land clearing and over-irrigation. These
activities result in groundwater rising to the surface, dissolving the salts and then depositing
them in the soil.
Groundwater is a layer of soil that is saturated with water that has slowly trickled down
through the soil until it cannot go any further because it is stopped by a layer of impermeable
soil or rock (bedrock).
Where does the salt come from?
Salt can be found in many old, highly weathered landscapes and originates from:
In undisturbed landscapes, most of the salt is slowly leached into the subsoil, beyond the
reach of plant roots.
There are two main forms of salinity: dryland salinity and irrigation
salinity.
(In Australia 2.2 million hectares of land is affected by dryland salinity and 160 000 hectares by
irrigation salinity.)
(Picture courtesy of the University of sydney)
Dryland salinity
Causes of dryland salinity
Salinity problems in the soil and surface water bodies occur when more water enters the
groundwater system (through a process called recharge) than is discharged from the system.
This imbalance causes the water table to rise. As it rises, the groundwater dissolves the
soluble salts stored in the subsoil and brings salty water into the reach of plant roots.
Evaporation and plant uptake of the water concentrates the salt in the topsoil - where it
stays.
The main cause of rising groundwater is the clearing of deep-rooted, perennial native
vegetation and its replacement with shallow-rooted, annual crop and pasture species. These
introduced species use less water than the native vegetation, resulting in increased
groundwater recharge and water table rise.
Land clearing is the past and present cause of dryland salinity. It takes approximately 30 years
from the time of clearing for dryland salinity problems to appear, although in some areas they
may appear sooner.
Why is dryland salinity such a problem?
The most obvious effect of salinity is the decline in agricultural productivity that is associated
with saline soils. High concentrations of salt in the soil are toxic to plants, restrict plant
uptake of water and prevent plants from taking up essential nutrients such as calcium.
Aside from declining agricultural productivity, salinity causes many other problems including:
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1. salinisation of groundwater aquifers and dams that supply water for human consumption, agricultural or industrial use.
2. damage to infrastructure on farms and in regional towns including roads, buildings, fences, railways, water pipes, water supply systems, houses, gas pipes, and gas supply systems.
3. loss of biodiversity as a result of degradation of remnant bushland, riparian vegetation, and wetlands
4. other land degradation problems such as wind and water erosion.
In addition to these economic and environmental costs, salinity also exacts a social cost. This cost includes the emotional and health-related costs of the family farm going bankrupt and the impact of facing the possibility the farm may not be passed onto the next generation...
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