Introduction to Soils and Soil Formation

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Introduction to Soils and Soil Formation

There are numerous different types of soils with distinctive profiles. Their formation in influenced by climate, geology, topography, and biological organisms. They are the thin surface layer of the Earth's crust.

Regolith: Weathering of parent material to give a layer of loose broken rock. True soil is topsoil and involves the addition of water, air, living organisms (biota) and humus.

Parent material: The supply of Minerals comes from underlying rock, which have different rates of weathering. It controls depth, texture, drainage, and quality of the soil.

Climate: This influences the rate of weathering of the parent rock. Precipitation affects the type of vegetation that grows in an area and then provides humus. Rainfall may lead to leaching if it is very heavy. If rainfall is light or evapotranspiration is greater than precipitation capillary action begins to operate where water and minerals are drawn to the surface.

Topography: This is the relief of land. On higher land precipitation, cloud and the wind increase but temperatures decrease which influence soil formation. Steeper slopes encourage throughflow and Surface run-off making mass movements more common. Soils are often thin and of a poor-quality. Soil Catenas such as the one below show how soil varies along a slope. Rock type is constant.

 Introduction to Soils and Soil Formation

Time: It can take 3000 to 12000 years to have sufficient depth of soil for farming.

Organisms (biota): Plants and bacteria, fungi, and animals all interact in the nutrient cycle.