Why do Soils Differ?
There are numerous reasons why soils differ regionally. The most
influential factors include the parent material (the rocks from
which the soil has come), the climate and terrain of the region,
as well as the type of plant life and vegetation present, and,
of course, human influence.
Parent material - this refers to the original
underlying rock upon which the soil formation takes place. Essentially,
the nature of parent rock in a particular region will affect the
type of soil that eventually develops. For example, in an area
of mainly sandstone, the soil formed due to the weathering of the
rock is likely to be well-drained, course and sandy.
Climate – The world consists of a broad
range of climatic regions, each with its own specific types of
soil. A common example of this is tundra soil, which tends to occur
mainly in northern-hemisphere areas such as the Arctic and Scandinavia,
where the climate is often cold and hence the organic materials
do not break down very easily and peat tends to form. In contrast,
red and grey ‘desert’ soils which are found only in
hot, arid regions, such as Africa and the Middle-East, contain
very small amounts of organic material because it is rapidly oxidised
under the warm conditions. These soils but are less leached than
the tundra soils.
Terrain – this is another important factor
in soil development. Areas with many slopes in the land tend to
have more freely drained soils, as water can run off or percolate
more rapidly. In contrast, regions with mostly flat areas of land
can often be waterlogged, because of the lack of gradient to promote
lateral or sideways flow.
Plants – The type of plant life and vegetation
obviously varies according to a region’s climate and other
factors. Plants also have a strong influence on soil development – they
take up nutrients from the ground, whilst adding organic material
to the soil surface.
Humans – We should not forget the influence
of man who has managed the land over the last few thousand years.
Agriculture, in particular, has had a big influence on developing
the soils we see today.