| Major
soil types
By
Marjorie Henry, Contributor
 |
(At front)
Kimar Wint (left) the top CXC performer at Bridgeport High School with eight CXC
passes; Kamekia Stobbs (centre) and Karyn McCalla reflect during the Bridgeport
High School's 28th anniversary on Friday, September 29. -
Photo by Anthony
Minott/freelance photographer | In
this week's lesson, I will continue to share with you, the information on the
two major soil types you are required to know, namely, latosols and rendzinas.
I will use the questions I gave you last week to recapitulate the lesson as I
continue the topic. Here are the answers: - 1.
'Soil order' is the classification of world soils based on global climate and
vegetation belts. 2.
The three soil orders are zonal, intrazonal and azonal. 3.
Latosols belong to zonal and rendzinas belong to intrazonal. 4.
Latosols develop in humid tropical and equatorial latitudes. 5.
Leaching is the soil forming process that is responsible for the development of
latosols. 6.
The natural vegetation found on latosols is an evergreen rain forest. The leaf
litter is high but the high temperatures cause the leaves to rot very quickly
leaving only a thin layer of litter covering the surface. 7.
Because of the strong leaching which occurs in this soil type, the silica content
of the soil is washed out leaving behind the iron and aluminium oxides. It is
the concentration of these minerals that gives latosols their characteristic reddish
colour. A
sketch of the latosols profile was missing from the lesson last week. It is absolutely
necessary that you can recognize a latosols profile. Practise to draw it also.
Here is a sketch of that profile taken from the text Principles of Geography
for CXC by Norrel A. London, et al. (See
image below)
Warm weather, heavy rain Let
us now turn our attention to rendzinas. You may recall that it was stated in last
week's lesson that rendzinas are an example of intrazonal soils. Here are some
characteristics of this soil type: - Rendzinas
are found in temperate and tropical areas. They are found in many Caribbean countries,
but only on a small scale. On the upland plateaus of Jamaica, rendzinas develop
on yellow limestone.
- The
nature of the parent material is the major factor influencing their formation.
They develop from parent material, such as marl, limestone or chalk. Chalk and
limestone release large amounts of calcium when they are weathered. This leads
to a soil that is rich in calcium carbonate.
- The
profile shows a dark-coloured top layer in which humus is uniformly distributed.
The underlying horizons are light in colour and rich in lime.
- Rendzinas
are thin soils. The 'A' horizon averages about 20-25cm and there is no true 'B'
horizon. The 'C' horizon is made up of the dominant limestone.
- Grasses
are the natural vegetation of rendzinas soils. The grasses produce a leaf litter
rich in bases. The leaf litter encourages considerable activity by organisms,
which help with the rapid recycling of nutrients.
- Rendzinas
are dark in colour from decayed plants mixed in with weathered limestone.
Here
is a sketch of the profile taken from the text The Caribbean Environment
by Mark Wilson: Review
the lesson by answering these questions: 1.
What is the major factor influencing the development of rendzinas? 2.
Why are rendzinas rich in calcium carbonate? 3.
Where in Jamaica do rendzinas develop? 4.
What contributes to the dark colour of rendzinas? Marjorie
Henry teaches at Glenmiur High School. | 
