Soil Erosion and Conservation
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SOIL EROSION AND CONSERVATION
Erosion
Erosion is the removal of soil particles by the motion of wind or water. Soil erosion is one of the major concerns of modern agriculture throughout the world.
The fallowing contributes to soil erosion:
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Misuse of land,
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Mismanagement of arable land,
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Indiscriminate felling of trees,
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Overgrazing,
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Poor soil and water management
Erosion causes or Results in a:
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Decline in soil fertility,
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Water supply,
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Crop yields.
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Thus it affects the productivity of the land,
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This decreases the production of food, feed, fiber, and fuel.
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This adversely affects the socio-economic conditions of the state.
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Erosion causes floods,
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Silting up of water reservoirs,
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Disruption of communication systems,
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Disturbance of the socio-economic setup of the farming community.
Erosion is of Two Types.
Normal or Geological Erosion:
Erosion effects are not visible on the land surface nor are soil productivity adversely affected. In quantitative terms, the amount of soil lost through erosion is equal to the amount of soil formed.
Accelerated Erosion:
The effects of erosion are visible on the ground surface and the rate of soil loss is greater than the rate of soil formation.
Magnitude of the problem in Pakistan:
According to an estimate;
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Wind and water erosion affect over 76% of the country’s total area.
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Over 36% is being eroded by water and 40% by wind.
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Every year approximately one billion tonnes of soil is being lost, silting up precious dams and dumped into the Arabian Sea.
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Most erosion takes place during the summer because about 60-45% of the precipitation falls in that season in the form of heavy downpours.
Erosion is mainly caused by two agencies: Wind and Water.
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Erosion caused by wind is called -wind erosion
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And that caused by water is called water erosion.
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These two processes are active around the world all the time.
Water Erosion
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Erosion caused by water is called as – water erosion
Mechanics of water erosion:
The first impact of raindrops on the soil is the breaking up of soil clods. This can only occur if there is no vegetative cover.
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When raindrops fall on bare, unprotected soil, soil clods are broken into small particles which are suspended in the accumulated water.
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Some of muddy suspension flows down the slopes in the form of runoff, and part of it percolates downwards into the soil.
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When the muddy suspension enters the soil, suspended material is deposited in the soil pores, which affects the infiltration capacity of the soil.
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The continuous deposition of solids seals the soil pores and the further intake of water ceases.
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Consequently more and more water is lost as runoff.
Forms of water erosion
There are four stages of soil erosion by water:
Raindrop or splash erosion
Sheet erosion,
(iii)
Rill erosion, and
Gully erosion.
Raindrop or splash erosion is the first stage of water erosion.
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Raindrops strike the soil surface with great force.
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Aggregates and clods are broken into smaller particles which are splashed into the air and the surface layer of the soil is compacted and peddled.
Sheet erosion is the removal of a thin layer of soil by water acting over the whole surface.
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Sheet erosion has damaged very fertile lands located on slopes, some of which have been eroded to a depth of about 15 cm.
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This causes great economic loss because it results in the loss of the most fertile soil layer and diminished soil productivity.
Rill erosion. The appearance of small rivulets on the soil surface is called rill erosion.
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This is a transitional phase between sheet erosion and gullying.
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These small channels can he smoothed out with suitable tillage practices and proper management.
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Rill erosion is visible on uneven and neglected lands in the Pothwar Plateau and western hilly areas.
Gully erosion is the last stage of water erosion and is the result of constant neglect of the land.
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Gullies are active & long as their sides are bare.
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They become inactive when they have been stabilized by vegetation.
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Gully erosion causes much more soil loss than any other form of erosion.
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The kind and condition