Saving Our Soils
Some common soil problems that we can see around us are erosion, acidity
and salinity. These can degrade landscapes, destroy habitats, affect agriculture
and reduce water quality. So why do these problems occur – and what
can we do about them?
Erosion – Plants and trees hold the soil in place.
That's why the clearing of native vegetation and overgrazing contributes
to erosion. When water falls on bare soil it can wash soil away. It's
also easy for wind to blow precious topsoils away and for streams to eat
in to bare riverbanks. Tree planting creates windbreaks and helps keep
soil on their land. Leaving vegetation along the banks of streams prevents
soils and nutrients from being washed into rivers where they can trigger
algal blooms.
Wind erosion exposes the roots of a eucalypt.
Acid soils – Australia has a high incidence of
acidic soils - soils with a pH less than 4.8 - usually where rainfall
is high. Because these soils can release toxic levels of aluminium and
other mineral elements, they can be toxic to plants. Soil acidity is a
particular problem in many of Australia's low-lying coastal regions, especially
in areas where mangrove swamps have been cleared. Coastal acid sulfate
soils (pH less than 3.5) are capable of manufacturing huge quantities
of sulfuric acid, which reduces water quality in rivers and estuaries,
often resulting in fish kills. This is another good reason to protect
coastal areas and fragile wetlands.
Saline and sodic soils - Salt-affected soils, both sodic
and saline, cover more than two-thirds of Australia. Soil salinity occurs
when extremely high levels of salts accumulate within the soil, allowing
only salt-tolerant plants to grow. Although sodic soils contain lower
levels of free salt than saline soils, the sodium attached to clay particles
in the soil causes soil structure to break down, leading to erosion and
waterlogging. Australian native vegetation is uniquely adapted to our
salt-affected soils and climatic conditions. Many of our native plants
are perennial, with a deep root system that takes full advantage of any
available water. This means that very little water is left to escape to
the deeper soil below the roots, which in turn helps prevent the vast
reserves of salt stored beneath our landscape from rising to the surface
and seeping into rivers and waterways.
Rising salt can damage the soil and kill plants.
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