Chemistry Reference
In-Depth Information
ity bringing about chemical and morphological changes of the soil. It is
important, therefore, to understand the correlation between the composition
of a soil and the ways it is altered by human habitation (Holliday 2004;
French and French 2002).
The nature and relative amounts of each one of its components deter-
mines the type of soil. The composition and size of the mineral particles (e.g.,
of quartz, feldspar, mica, clays, salts) determine the texture of the soil. The
relative amount of organic matter affects its water-carrying capacity, loose-
ness, and fertility. Water, which makes up the liquid component and, in its
vapor form, part of the gases in the soil, is an effective temperature regula-
tor of the soil. It also transports salts and nutrients from the mineral and
decaying organic matter particles to the roots of plants and to other organ-
isms. The gases in the soil, which include, in addition to water vapor, mostly
nitrogen, oxygen, and carbon dioxide from the air, occupy pores and crevices
between the particles and are essential to the life of all living organisms in
the soil (see Fig. 47) (Hassett and Banwart 1992).
FIGURE 47
The main components of soil.
Soil consists of a mixture of solids, liquids,
and gases. The solid part includes minerals particles derived from weathered rocks
(mostly clay and sand) and organic matter (humus) resulting from the decay of dead
plants and animals. Water makes up the liquid and air, the gaseous part. The relative
amounts of each one of these components determines the type of any particular soil.
The diagram illustrates the composition of an “average soil” from temperate zones.
Dessert soil may contain as little as under 1% organic solids, while some wetlands and
bogs there is well over 30% organic solids.
