Be Prepared for Life
Activity Kit Five:
"Living with the Soil"
Part 1. Knowing our Soils
DO YOU KNOW -
Plants obtain all their water and the 16 nutrient elements they need from the
soil through their roots. Good soil is full of tiny spaces through which roots,
nutrients and water can come together. Different types of plants need different
types of soils to grow in. We need a detailed knowledge of our soil to protect
it and use it effectively. The quality of our lives depends upon this knowledge.
South Africa is not a rich farming country. Less than 14% of our soils are suitable
for crop farming.
THAT THE SOIL IS THE STOREROOM OF LIFE?
Understanding soil can make the difference between use and misuse leading
to prosperity or poverty.
Project 1: What kind of soil do I have?
- There are three soil types which are classified by their particle
Pick up a handful of soil. Wet it a bit and roll it into a sausage in
- CLAY soils have the smallest particles [<0,002 mm].
- SILT soils have medium size particles [0,02-0,002 mm].
- SANDY soils have large particles [2,0-0,02 mm].
- LOAM soils are mixtures of the above soils.
THE RING TEST FOR SOILS
||THE SOIL IS
|Cannot be rolled into a sausage
|| Illustations to come...
|Can be rolled into a sausage but can't be bent
|The sausage can bend a little
|Sausage bends half way round finger
||LOAM OR SILT LOAM
|Sausage bends more than half way round finger
||CLAY LOAM OR SANDY CLAY
|Sausage bends into a ring
|Sausage bends into a ring with cracks
||A SHORT CLAY [See Project 8]
|Sausage bends into a ring no cracks
||A FAT CLAY [See Project 8]
- If you suspect you have a loam soil collect half a jar
of soil. Top it up with water. Put the lid on and shake it well. Allow
it to stand until you can see the mixture of soil particles separating
into bands. Once the water has cleared measure the thickness of each
band. The sand will settle to the bottom, then the silt and finally
Organic matter will float on the surface. Try to use this graph to work
out what type of soil you have.
Plants grow best in well drained soils which retain moisture and have
plenty of plant nutrients in solution.
This is a description of a loam mixture.
Clay soils can be improved by mixing well with sandy soil and sand can
be improved by mixing well with clay.
- In places that have a lot of rain, plant foods like calcium, magnesium
and potassium are washed out of the soil. These soils become acid [sour]
and may need to be sweetened with lime, before grow well. Measure the
acidity of your soil using universal indicator paper or indicator solution
or a soil pH meter [obtainable at a nursery].
A swimming pool test kit can only measure a small part of this range
of soil acidity. Shake up a soil sample in a small amount of water and
pour it through coffee filter paper. Use the solution for your acidity
test. Most plants will tolerate a range of soil acidity, but prefer
slightly acid soils [pH 5 to 7; pH 7,0 is neutral soil].
|CABBAGES tolerate pH
||5,0 - 6,0; like
||5,5 - 7,0
||5,5 - 6,0
||5,5 - 7,5
||6,0 - 7,0
- The soil at the surface is the oldest and richest soil.
Dig a deep hole or find a nearby cutting where you can take samples
at different depths.
The surface layer is called the ORGANIC layer if there is a leaf
litter or plant cover. This is the living protection of the soil.
Below this is the topsoil layer or A layer. This is the living
part of the soil and it is often dark with decaying plant matter.
Clays tend to be washed down into the deeper B layer of the sub-soil.
Beneath this the soil becomes very stony in the region of weathering,
the C layer.
Finally the parent rock or R Layer is reached.
Measure the thickness of each layer in your profile. Compare it with
soil profiles from other areas.
Collect a sample of soil from each level as you reach it.
- Prepare four germination domes from 2 liter cool drink bottles for
your four soil samples. Label each sample after the region where it
was collected from and plant fast growing seeds in each dome eg. Sunflower
Compare the grow of the plants in each soil layer.
Which is the best soil layer for growing plants?
What will happen if the top soil layer is lost by erosion?
Not all soil is equally fertile! The best soil at the surface is the
most at risk today. Each centimeter of our soil takes about 500 years
to form. It will takes almost 15 generations of careful land use to
allow a single centimeter of soil to accumulate here.
DO YOU KNOW -
...allowing the soil to make its own fertility or adding it as fertiliser.
THERE ARE TWO WAYS OF FEEDING SOIL...
African soils are fragile. Our soil needs to be given time to rest between crops.
Decomposed plant matter [humus] needs to be allowed to build up in the soil, feeding
the animals that live in the soil, that in turn release more plant nutrients.
Where animals graze on grasses their dung must be allowed to replace the nutrients
they remove. Sadly, many desperate African farmers, have been forced to farm
land that should never have been ploughed. Often there are too many animals
grazing the ground. This happens when too many people live in the same area.
Animal dung is collected and burnt. The plant cover is eaten away or ploughed
away. The rains fail and the crops die. Winds blow the topsoil away. Rains wash
loose soil away. Soil is lost, soil animals die and soil fertility drops. People
begin to starve. Africa has known serious famines since 1960.
Since 1985 we have been unable to provide all our own food. In order to produce
more food farmers are often forced to add plant fertilisers to the soils. These
strong chemicals may destroy soil animals that release natures plant nutrients.
The soil is there, but dead! It becomes necessary to keep adding fertilisers
at rising costs to produce more food on dead soil.
Project 2: Is your soil alive or dead?
Soil animals recycle plants and animal remains back to other living organisms.
Living soil is full of life. Care needs to be taken not to kill these animals
by over fertilising with artificial chemicals. Compost your soil as much
- Collect a 400 g moist compost
[Kit 1: Project 11].
- Spread 200g in a white enamel bowl.
- Dissolve 3 tablespoons of salt in 500 ml of water.
- Pour the salt solution over the sample.
- Collect the animals that come to the surface with a fine paint
brush and place in fresh water.
- Did you see any of these animals?
Examine your specimens with a hand lens.
- Place the other 200 g of compost in a kitchen sieve and support
it in a funnel over a jar of water. Hang a 40 watt light bulb about
5 cm above the soil sample for two or three days.
Examine the very tiny animals that fall into the water as the sample
[ A microscope is a great help - but many can be seen with a hand
lens, floating on the surface].
- Make your own worm farm. Make a frame as in this illustration and
fill it with compost enriched loam.
Pour 200 ml of water into the wormery.
How long does it take to drain through?
- Collect 20 earthworms from your garden and place them in the wormery.
- Cover the wormery and keep it in a dark cool place.
- Place chopped weeds, leaves and grass on the surface.
What do worms eat?
- After a month - pour another 200 ml of water into the wormery.
How long does it take to drain through this time?
How do earthworms benefit soil?
Part Two: Saving our Soil
| © Copyright 1991 - 1994
Dr Frank Opie for the South African Scout Association