Geoscience Reference
In-Depth Information
It is located on this diagram by the intersection of lines parallel with the appropriate
sides of the triangle. Another way of viewing the difference between contrasting soil
types, such as those labelled A and B in this figure, is to show the relative proportions
of sand, silt and clay as circular diagrams. Soils with less than 30-35 per cent clay are
called loams - sandy loam, silt loam, clay loam etc - and these include our most com-
mon agricultural soils. Some deposits that are particularly rich in clay are quarried for
brick making.
T
ABLE 2
Identification of soil textures by hand. The following key provides a guide to five
distinctive soil texture classes. A subdivision of 'sands', 'loams' and 'clays' into the
11 classes in
Figure 1.4
can be done in a similar way. Take about a dessertspoonful
of moist soil and knead it thoroughly between finger and thumb until the aggregates
are broken down. Wet it if necessary until the soil exhibits its maximum cohesion.
1. Is the moist soil predominantly sandy?
Yes →
2
No →
3
2. Is it difficult to roll the soil into a ball?
Yes →
Sands
Light
loams
No →
3. Does soil mould to form an
easily deformed
ball and feel smooth
and silky?
Light
silt
Yes →
No →
4
4. Does the soil mould to form a
strong
ball which smears but does
not take a polish when rubbed?
Clay
loams
Yes →
or
Does soil mould like plasticine, take a polish and feel sticky when
wetter?
