Soil - Fundamentals of Tropical Turf Management - page 40

Water 25%

Mineral matter 45%

Air 25%

Organic matter 5%

Fig. 3.1. Soil is composed of minerals, air, water and organic matter (humus).

Successful management of turf requires familiarity with the essential
components of soil, their basic physical and chemical properties, their
role in the soil and their influence on development of plants. Proper
management of soil is essential in successful management of turf.

Soil Texture

The term soil texture describes the size of the individual mineral particles
and the proportion of each size in the soil The largest soil particles are
called sand , intermediate particles are called silt and the smallest particles
are called clay . According to classification adopted by most countries,
sand consists of particles ranging from 1 mm (in some countries 2 mm)
to 0.05 mm in diameter. Silt consists of particles ranging from 0.05 mm to
0.002 mm (in some countries 0.02 mm). Clay consists of particles smaller
than 0.002 mm in diameter. Figure 3.2 shows the relative sizes of these
types of soil particles. If the sand particle were the size of a basketball, a
silt particle would be the size of tennis ball and a clay particle would be
smaller than a grain of rice.
Soil types are based on texture. For example, sandy soils are those
that contain a high proportion of sand particles, and clayey soils are those
containing a high proportion of clay. Soils containing a high proportion
of silt, however, are usually called loamy rather than silty. On the basis of
the proportions of sand, silt and clay particles, distinct soil textural
classes have been defined. Classification differs slightly in different coun-
tries, but patterns are similar. Soils containing primarily sand and silt are
called loamy sands or sandy loams. Increasing amounts of clay could
result in a sandy clay loam or sandy clay. Soil that consists of roughly the
same percentages of sand, silt and clay is classified as a clay loam. The
textural triangle shown in Fig. 3.3 presents 12 textural classes and is the
most commonly used around the world.