WEEK 9
SUBJECT: AGRIC
SCIENCE
CLASS: GRADE 8
TERM: SECOND
TOPIC: SOIL AND
WATER CONSERVATION (CONTINUED)
PREVENTION AND
CONTROL OF EROSION:
Prevention
and control of erosion in other to conserve the soil can be achieved through
the following practices.
(a) Covering the
land with vegetation:
Covering the soil with plants prevents the soil from being exposed to agents of
erosion such as water and wind. The planting of cover crops is to maintain
adequate ground cover. Soil fertility is also increased because of leaf fall.
Water infiltration is encouraged and run-off is reduced because of the
vegetative cover.
(b) Crop
rotation: A well designed crop rotation ensures that the land is always
protected against erosion. Where legumes are included in the rotation, they
help to control erosion because they spread over the soil surface.
(c) Application
of organic and inorganic manures: The addition of compost and farm yard
manures makes the soil cohesive and absorbed water. They also add plant
nutrients to the soil. The addition of lime fertilizers such as calcium
trioxocarbonate (iv) to the soil causes loose soil particles to be bound
together. This improves the structure of the soil and the soil cannot be
carried away easily whether by water or wind.
(d) Mulching: This involves
covering the soil with mulch materials such as papers, grasses and stones. It
prevents direct contact between the soil and raindrops, increases water
infiltration and reduces sheet erosion. Where mulching is done with plant
materials, organic matter is added to the soil. This helps to bind loose soil
particles together.
(e) Preventing
bush burning: Setting
the bush on fire destroys the covers for the soil. During bush burning, organic
matter and many agriculturally important living organisms are destroyed. The
soil is therefore exposed to agents of erosion. Where bush burning is avoided,
the organic matter and micro-organisms present help to improve the soil
structure and control erosion.
(f) Preventing
overgrazing: Overgrazing
of pasture or field could occur if animals are allowed to remain for long time
on the same land. Almost all vegetation in such a place is eaten up and will
not have time to grow again. Such land is exposed to erosion agents.
(g)
Establishment of wind breaks: The planting of trees prevents erosion
by acting as wind breaks. This is a good erosion preventive measure especially
in the savannah regions and where the soil is sandy.
(h) Contour
strip cropping: This
involves the growing of close growing plants such as grasses and row crops such
as maize in alternate strips across the slope of the land. This ensures
adequate cover for the land. It therefore reduces the speed of moving water and
its load.
(i) Terracing: Terraces are
embankments constructed across the slope at regular intervals to conduct water
away from the land in such a way as to keep erosion under control. They reduce
the length of slope that may aid erosion. Terraces are built in form of steps
along the contour of the land or across the slope.
(j) Ridging: The construction
of ridges during land preparation, as well as tied ridges help to control soil
erosion. Ridges enhance water absorption by the soil and this reduces the speed
of run-off.
(k) Construction
of contour bunds: The
construction of ridges called bunds across the slope prevents soil erosion. The
contour bunds prevent water run-off down the slopes.
(l) Erection of
Barriers: Barriers
can be created at intervals in gullies to reduce the speed of water run-off.
Dams of earth blocks, concrete or stones can be used to fill gullies already
created. These help to trap sediments which eventually fill the gullies.
WATER
CONSERVATION: Soil
water loss can be prevented or minimized by carrying out the following
practices:
(a) Maintaining
vegetative cover: Covering
the land with plants prevents excessive drying of the soil. It also prevents
direct evaporation of soil water.
(b) Good
cultivation methods:
This involves tillage. Tillage encourages the soil to absorb water and prevents
run-off. Contour ridging or ridging across slopes helps to reduce water
movement down the slope and thereby encourages infiltration.
(c) Use of
organic manure: This
refers to the addition of farm yard, compost or green manures to the soil.
These provide cover for the soil. Organic manures bind soil particles together
and enable the soil to hold water.
(d)
Controlled burning practices: The burning of the farm during land
preparation should be done when no other way of disposing off farm trashes is
available. Burning should therefore be carried out when it is very necessary.
(e) Mulching: The use of mulch
materials to cover heaps, beds and ridges helps in conserving soil water.
Mulching prevents evaporation and excessive drying by the sun.
(f) Terracing: This helps to
reduce the length of slopes and decreases run-off. Water infiltration is then
encouraged.
(g) Use of wind
break: The
planting of trees protects the soil against excessive drying by the sun and
strong wind. The trees produce cooling effect on the soil.
(h) Regular
weeding: The
removal of weeds from the farm reduces unnecessary transpiration. Enough water
is therefore conserved for crop use.
(i) Breeding
drought resistant crops: The development of crops that use little water will
enable the soil to retain most of its water.
(j) Strip
cropping: This
involves the growing in alternate strips, of different crops in the same field.
It ensures that the entire land area is not empty at the same time.
HUMAN ACTIVITIES
WHICH CONTRIBUTES TO LOSS OF SOIL FACILITY:
1.
Crop removal
2.
Burning
3.
Tilling
ASSIGNMENT
Theory
Questions:
1.
Mention five ways of preventing and controlling erosion.
2.
Mention five ways of conserving water lost.
3.
State three human activities which contribute ton loss of soil facility.
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