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2.6 SOIL SAMPLING AND ANALYSIS
Literature review
Soils are complex systems high in spatial variation. It universally consists of three
phases; solid, liquid and gas (GLASS, 1989). The solid phase contains the major
inorganic reserves of the soil, the liquid phase contains a source of nutrients that are
immediately available for uptake by the roots and the gaseous phase permits
exchange of gases, the most important of these gases being oxygen, carbon dioxide
and nitrogen (GLASS, 1989). In addition to these physical phases soil also contains a
wide variety of biota including a diverse community of interdependent plants, animals
and microorganisms. Other definitions are that soils generally consists of the rocks
and their weathering products, substances formed by reactions within the soil profile
and material from plants and animals (SLEEMAN & BREWER, 1988) and that soil is
a multilayer granular composite originating from larger rocks (LECLERC, 2003). Just
by looking at the diversity in these explanations and definitions, it is clear that soil is
very complex, and its study is very interdisciplinary. Although soil is so complex and
creating a complete list of all the constituents of soil would be very difficult and has
not been attempted, Figure 2.29 shows some of the general constituents of soil
(SLEEMAN & BREWER, 1988)
The mineral content of soil is the result of this weathering of larger rocks, climate,
necrosis and decomposition of biota and the action of soil micro biota (LECLERC,
2003). The organic matter content of soil originates from the necrosis and
decomposition of cells, tissues, organs and whole organisms (LECLERC, 2003). The
nature and type of a soil is determined by the rock it originates from, the climate and
the surrounding biota (LECLERC, 2003).
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