Factors influencing soil formation

Factors influencing soil formation

These are responsible for the type and nature of soil formed in an area;They are mainly five and they include;

  • Time
  • Topography
  • Living organisms
  • Climate
  • Nature of the parent rock

Nature of the parent rock; This refers to the materials from which soil is formed.

The type of rock determines the type of soil formed e.g. Sand stones give rise to sandy soils, volcanic ash rocks give rise to very fine soils.

Parent material affects the colour of the soil formed.

Parent material determines the ease of weathering i.e. soft rocks e.g. igneous rocks are easier to break down.

Parent material determines the depth of the soil formed e.g. soft igneous rocks produces deeper and more fertile soils than hard sedimentary rocks.

Climate; Climatic factors that influence soil formation includes temperature, rainfall, wind.

Effect of temperature

Alternate expansion and contraction of rock surfaces due to temperature changes of day and night causes cracking of rocks to form soil.

Increase in soil temperature results in evaporation of soil moisture to form rain which is a weathering agent.

Temperature affects the rate physical and chemical weathering.

Temperature affects the rate of activities of soil living organisms (increase with increase in temperature within a given range).

High temperatures cause peeling of the rock surfaces (exfoliation).

At higher altitude in rock crevices, when temperatures are low, water changes into ice that exerts pressure and causes rocks to crack.

Effect of rainfall

Direct impact of rain drops on rocks dislodges small particles which are later weathered to form soil.

As rain water flows down the stream and rivers, it carries rock particles which knock each other to form soil.

Rain dissolves carbon oxide in the atmosphere to form weak carbonic acid which dissolves rocks.

Rain water provides moisture needed by micro organisms to decompose organic matter.

Running water helps to remove accumulated materials from the rock surface hence exposing the soil to more agents of weathering.

Effect of wind

Wind blows sand particles against rocks causing abrasion of the rock surface.

Wind carries away rock materials and deposits them else where to form soil.

Living organisms

Roots of trees grow in the cracks widen the cracks causing the rocks to split.

Burrowing animals e.g. rodents break down soft rocks and help in soil profile mixing.

Earthworms and termites feed on dead organic matter and decompose it.

They mix organic matter with top soil hence forming a little crumby structure.

Animal hooves break the rock surfaces that they walk on.

When living organisms die, they decompose and form organic matter that improves on soil fertility.

The tips of plant roots secrete chemicals at their tips that help to dissolve rocks.

Fungi and algae colonize the rocks and secrete chemicals which dissolve the rocks.

Man’s activities e.g. mining, digging, quarrying etc influence soil formation in various ways.

Topography

This is the nature of the surface of the land.

This affects the rate of weathering, soil depth and nature of the soil formed.

Topography affects local rainfall distribution through creation of rain shadow areas.

Up the mountain, there is decreased temperature and hence reduction in the rate of weathering.

Topography influences the depth of soil formed in the valleys where the weathered materials are deposited

Topography influences the rate of water infiltration into the soil i.e. lower infiltration on steep slopes affects chemical weathering.

A steep area does not encourage accumulation of weathered materials but encourages transportation and deposition occurs down the slope.

Topography influences rate of erosion i.e. less erosion on gentle slopes and more erosion on steep slopes.

Time  

Soil formation is a very slow process that takes a lot of time to take place.

The longer the time the rock is exposed to agents of weathering, the deeper and fertile the soil will be.

The clay content of the soil increases with time.

soil formation process

These include the following:

Disintegration:  this is the breaking down of rocks into smaller particles.

Decomposition: the further breakdown of rocks into very small soil particles it makes the soils to release nutrients to the plants.

Translocation: this refers to the removal of the soil. The soil is carried away by running water and wind.

Deposition: the soil particles carried away by water and wind are deposited to another area.