Geoscience Reference
In-Depth Information
1
The nature of Australian soils
A soil consists of a mixture of sand, silt, clay and organic matter in varying
proportions, which at first glance looks as if it should be reasonably easy to
understand. When looking more closely at the make-up of fertile soil, it is seen to
be a complex, ever-changing matrix supporting a complex living ecosystem.
The ecosystem consists of plants, which in turn support, and themselves
depend on, a range of larger organisms such as insects, mites, spiders, earthworms
and ants, not to mention livestock and other grazing animals. There are also small
organisms including bacteria, fungi and actinomycetes, such as mycorrhiza, that
are active in converting nutrients to plant available forms.
Fertile soil is dynamic and changes over time depending on moisture,
temperature and the way it is managed.
It is true to say when farming soils, the production of crops and livestock is
directly proportional to the microbiological content of the soil.
The origin of Australian soils
Soil is initially formed from weathering of bedrock, and the type of soil formed is
determined by the type of rock that it is formed from. Obviously, there are large
differences between rocks such as granite, basalt and limestone, and the soils
formed from these rocks show large differences as well.
Water is one major factor in soil formation, transporting weathered rock from
hills to valleys and depositing the rock particles initially on the slopes of the hills
and later in layers in the valleys.
