Geoscience Reference
In-Depth Information
23
Soil structural decline
What is soil structure?
Soil in good physical condition should have a soft porous, crumbly structure,
where small soil particles have formed into aggregates. These aggregates are
numbers of soil particles glued together by clay and organic compounds such as
humus.
The formation of soil aggregates leaves spaces between them that will contain
water and air (oxygen), and provide easy access for plant roots.
Not all soils have this type of structure in the native environment. For
example, sandy soils with low levels of organic matter are fragile, are easily
damaged and have poor water holding capacity. At the other extreme, heavy blocky
clay soils composed of very fine particles are very dense, with small pore spaces
and hold water tightly.
An ideal soil is one with well-formed aggregates in a loose-packed arrangement
that is not easily broken down by water, stock or machinery.
Assessing damage to soil
Loss of surface structure
A soil with a damaged surface structure will be powdery and cement-like when
dry, and muddy and pond water when wet.
Plant growth will be restricted and wet soil will probably be waterlogged.
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