HOW HUMAN
ACTIVITIES CAN
PREVENT SOIL
EROSION
(CONSERVE
SOIL)
Methods of soil conservation (ch3)
The key aspects discussed in this chapter are:
•
•
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Windbreaks
Contour ploughing
Stubble planting
Terraces
Stone walls
Reduce farming in dry weather
• Windbreaks
• Reforestation
• Farming
techniques
.
Replacing and Improving
Vegetation Cover
Improving water control and
reducing surface run-off.
Improving farming methods.

Replacing and Improving Vegetation
Cover
If the most serious cause of
soil erosion is the removal of
vegetation cover, then the
best protection is likely to be
the planting of vegetation.

Afforestation (growing /
planting trees) is a long term
solution because growing
leaves intercept rain drops
and so rain-splash damage
is lessened.

Vegetation roots bind
(hold) soil particles
together and this reduces
surface run-off and so
lessens gully erosion.

Gully Erosion
Tree roots absorb moisture from
the soil and this reduces the
weight and lubrication of the
soil.
Thus, the possibility of soil creep
or mudflows (sheet erosion) are
reduced.

The growing of cover crops (grass,
brushwood) for short periods on newly
ploughed land also reduces run-off
and rain-splash effects by covering
and binding the soil.
 The grasses will trap wind-blown soil
and the roots will bind the soil e.g.
Prairie lands of the USA and Canada.

Brushwood
In Ireland, stubble (small amount of
vegetation left in the ground after the
cutting of cereals) planting has helped soil
conservation.
 In the past the stubble was ploughed back
into the soil to improve fertility.
 Now the stubble is left on the surface and
it’s roots reduces water and wind erosion
by binding the soil together.

The planting of trees as wind breaks
(barriers formed by trees) around the
edges of fields is an essential form of
soil erosion prevention.
 The windbreaks stop the wind from
blowing the soil away, especially if
they allow a little wind to pass
through.

If wind is stopped completely violent
wind gusts at ground level can lift the
soil into the air and it is blown away.
 To avoid this, there are usually 2 lines
of trees in each windbreak – one line
of large trees and a second line of
shorter trees.

The addition of humus (dead plant
litter) from the vegetation also helps
to reduce soil erosion as the humus
absorbs and retains water.
 This reduces the chances of the soil
drying up and being blown away by
wind.

Improving Water Control and Reducing
Surface Run-Off
Water wells sunk in dry climates use up
reserves of groundwater and this results
in a fall in the water-table.
 This makes it harder for plant roots to
obtain water and the soil dries up.
 Careful control of well sinking and the
amount of water use would reduce this
problem.

If contour ploughing – tractors
plough around the sides of a hill
and not up and down is used, then
small furrows or ridges are made
in the soil.
 These ridges give the water time to
soak into the ground e.g. Mid-West
USA.

Gully erosion is reduced
as the surface water does
not flow straight down the
hillside and pick up the
topsoil.

If hill slopes are too steep for contour
ploughing then terraces can be built
on the slopes.
 Terraces are a series of parallel walls
built on the hillside one above the
other.
 Behind each retained wall a terrace
of land (step) is flattened out and
crops are grown

The tops of the walls act as dams as
they trap water and stop the water
from running down slope and they
stop soil particles from moving
downhill.
 So gully erosion is prevented as the
speed of the water is reduced e.g.
Rice growing areas of China,
Vietnam.

The building of simple stone walls (bunds) in the
Sahel Region of Africa is a simple water control
measure.
 People place lines of small stones along the
contours of hills.
 Rainwater gets trapped behind the stones and this
allows the water to percolate (soak) into the
ground rather than running straight downhill.
 This reduces the amount of surface run-off.

The stone walls (bunds) can
also stop any soil in the water
moving down slope as they act
as filters and trap soil
particles.
They are most effective on
gentle slopes.

If salinisation is occurring due to irrigation
then the salt concentration kills plants and
makes the soil surface hard and often
impermeable.
 The soil can be blown away by wind in the
dry season.
 To prevent this, water must be continually
flushed through the system or else grow
crops which require less irrigation e.g. In
Australia.

Improving Farming Methods.



Growing the same crop every year on the same piece of
land repeatedly uses up the same nutrients.
This often means that the soil becomes infertile and
vegetation won’t grow so the soil becomes loose and
open to wind erosion.
Crop rotation – (the planned growth of different crops in
the same place from year to year) – ensures that some
minerals are not taken away so the soil remains fertile
and erosion reduced.
Crop Rotation
The reduction of ploughing in dry and
windy weather reduces the risk of wind
erosion as the ploughing loosens the soil
and breaks up any stubble binding.
 As there is no rain to dampen the soil and
make it heavier, the reduction of
ploughing gives the soil a better chance
of survival e.g. Mediterranean regions in
Spain.

If the ploughing is too deep then the
soil structure is destroyed by the
breaking up of peds and burying
humus too deeply.
 As there is no vegetation to bind the
soil, the topsoil is often blown away,
so deep ploughing should be
avoided.

The regular addition of organic
matter (natural fertilisers) in
farming provides food for soil
organisms and binds the soil
together so there is less chance
of loose soil and wind erosion.

The addition of organic matter to
soils makes the soils more resistant
to the impact of farming machinery
and livestock.
 The resistance means less
breakdown into fine soil particles so
soils are less prone to wind erosion.

Extra organic matter means that
higher levels of nitrogen remain in
the soil and this increases humus
growth and water retention.
 So soils are less prone to wind
erosion.

If evaporation exceeds rainfall in the dry
season e.g. Mediterranean regions, then
dry farming can be adopted.
 This means covering the soil with a mixture
of straw and weeds to reduce moisture
loss.
 This allows the binding of the soil to
continue and reduces wind erosion of dry
loose soil.

Dry farming
By adding humus or clay to sandy soils
the water holding capacity is increased
as the humus / clay can retain water.
 There is less likelihood of the soils drying
up so the threat of erosion is reduced.
 This method is expensive and it is used
mainly in developed countries e.g. France.

Possible Question
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Examine the causes of soil erosion and how human
activities can prevent soil erosion.
Marking scheme: 3 paragraphs at 27m+27m+26m
In this type of answer the method that should be used is:
2 causes of soil erosion and 1 human activity to prevent it
Or
1 cause of soil erosion and 2 human activities to prevent
it.