Environmental Engineering Reference
In-Depth Information
3
Soil
Soils of the tropical regions of the world are extremely diverse. They
range from the poor arid and semi-arid soils, which are low in organic
matter, to the humid tropical soils, which are relatively high in organic
matter and more fertile. Because high temperatures persist throughout
the year, as does high humidity in some areas, microbiological and
chemical activities in tropical soils are much faster than those of the
temperate regions. Rainfall is often seasonal, sometimes excessive and,
in some areas, abundant year-round. The information included in this
chapter pertains to the general properties of soil that are typical for most
tropical regions.
Soil is the material that covers the surface of the earth, whenever that
surface is not bare rock. It can be formed by the forces of nature or be
built up artificially. Soils used in crop production are usually natural,
whereas those under turf-grass are often artificial, composed of material
brought from elsewhere.
Soil consists of four major components: (i) minerals, (ii) air, (iii) water
and (iv) humus (Fig. 3.1). Minerals are inorganic substances, originating
from rock. Air and water fill the gaps between minerals. Humus is
organic material originating from living sources.
All soil components influence each other and form the environment
in which plants grow. If this environment is well balanced - i.e. if it
contains adequate amounts of water, air and all necessary nutrients in the
right proportions - the result is a fertile soil.
The basic functions of soil are to provide physical support for the
turf-grass plants and to supply moisture, air and nutrients to the roots.
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