SOIL EROSION

WHAT IS SOIL EROSION?

Soil erosion is the dislodgement of soil particles or the wearing away of the earth’s surface by the action of water , wind etc. Soil erosion is a

natural process but becomes an issue when the rate at which the soil particles are lost is faster than the rate at which they are replaced. This is

called accelerated erosion and is caused by human impact such as over-grazing, poor

agricultural practices etc.

Types Of ErosionThere are two (2) types of erosion, namely: Geologic Erosion

Geological erosion goes on continuously, it causes the wearing down of land masses providing material for soil formation essentially therefore it is influenced by climate, soil properties, vegetation and topography.

Accelerated ErosionThis type of erosion is brought about by man

usually in his attempt to produce crop from the land or to clear the land for commercial or industrial purposes in so doing he exposes the land to one or more of the agents of erosion.

Agents of Soil Erosion• Wind

• Water

• Animals

• Man

Soil Layer

Natural FactorsWater ErosionWindSteep slopes Climatic Changes

Human Induced-Factors Deforestation Poor Farm Practises Animal Induced Factor Over Grazing

What are the causes of Soil Erosion?

Water erosion is the dislodgement, transportation & deposition of soil particles by the force of water from one location to another.

Water Erosion

• Splash Erosion First stage of soil erosion process. When raindrops hit bare soil, it loosens soil particles and water transport them downhill.

Forms of Water Erosion

Sheet erosion is the removal of soil in thin layers by raindrop impact . It results in loss of the finest soil particles that contain most of the available nutrients and organic matter in the soil.Soils most vulnerable to sheet erosion are overgrazed and cultivated soils where there is little vegetation to protect and hold the soil. Early signs of sheet erosion include bare areas, water puddling as soon as rain falls, visible grass roots, exposed tree roots, and exposed subsoil or stony soils.

• Sheet Erosion

Rill erosion is erosion that results in small, short-lived and well-defined streams. When rainfall does not soak into the soil, it can gather on the surface and runs downhill, forming small channels of water called rills. A rill will dry up after the rainfall, but you may still see the stream bed that was created by the temporary stream.

• Rill Erosion

Gully Erosion are advanced rill erosion. If rill erosions are not addressed they grow into gully erosions.

• Gully Erosion

Wind erosion is the detachment and movement of soil particles by air moving. Wind moves the soil in two ways, suspension and saltation. Suspension occurs when the wind lifts finer particles into the air leading to dust storms. Saltation occurs when the wind lifts larger particles off the ground for short distances, leading to sand-drifts. Wind erosion tends to occur most in low rainfall areas when soil moisture content is at wilting point or below.

• Wind

rainfall: when rainfall becomes more severe, erosion increases rapidly.

drought: Drought can cause soil erosion due to the effects of wind and flooding. Moreover, the drying out of soil causes cracks which reduce the volume of the soil.

changing winds: areas previously sheltered become exposed

Climate Changes

Cultivating along steep slopes results in gully erosion taking place.

Steep Slope

Deforestation is the full or large scale removal of a forest, or areas of trees transforming it in to clear land for human development. This leaves the soil bare or exposed which becomes prone to erosion by wind and water.

Human Induced Factors

• Ploughing- when farmers use machines for ploughing on the farm it squashes the soil creating channels for rapid water run-off.

• Monoculture/Fertilizers-Monoculture leads to exhaustion of certain minerals from the soil making it infertile, bare and leading to soil erosion

Monoculture leads to the loosening of soil particles thereby encouraging soil erosion.

Poor Farm Practises

Adding fertilizer increases the acidity of the soil/changes the PH of the soil. The acidity destroys the micro-organisms in the soil, which could have helped in the formation of humus, which binds soil particles together Acidic soils are unsuitable for various crops, which could have helped protect the soils from erosion

• Burning destroys micro-organisms which are essential for the formation of humus, which bind soil particles together.

• Burning destroys vegetable matter that protects the soil against erosion

• Burning destroys the nitrogen fixing bacteria making the soil less fertile

• Burning loosens the soil making it susceptible to erosion/leaching which drains away soluble mineral nutrients

• At the top, soluble minerals come into contact with insoluble ones

When farmers allow too much animals to graze an area of land, it damages the soil structure and removes its cover making it bare and exposed to erosion by wind/water.

Overgrazing

• Increase in number of channels across land.• The settling of muddy water at lower

surfaces of the land.• The exposure of roots of trees and shrubs.• Landslides loss of houses, lives etc.• The blocking of drains and ditches which

leads to flooding.• Reduction of soil fertility, resulting in

decrease in crop yield.

Effects of erosion

• Reforestation• Rotational grazing

Solution to Soil Erosion