The thin layer on the surface of the Earth on which the living beings of the earth survive since it is the layer of materials in which plants have their roots.

FACTORS CONTROLLING SOIL FORMATION

Five Major Factors That Influence Soil Formation•Parent Material

•Climate•Living Organisms (especially native vegetation)

•Topography•Time

Parent Material

Refers to organic and mineral material in which soil formation begins.

 ClimateA major factor in determining the kind of plant and animal life on and in the soil.

Living Organisms

Plants affect soil development by supplying upper layers with organic matter, recycling nutrients from lower to upper layers, and helping to prevent erosion. 

TOPOGRAPHY ( Landscape Position)

Refers to the point on the landscape where the soil is located.

 Time

The longer a soil surface has been exposed to soil forming agents like rain and growing plants, the greater the development of the soil profile.

TYPES OF SOIL

Soil can be classified according to the following types:•Sandy soil •Silty soil •Clay soil

•Loamy Soil •Peaty Soil

•Chalky Soil

Sandy Soil

Has the biggest particles and the size of the particles does determine the degree of aeration and drainage that the soil allows.

Silty Soil

Granular like sandy soil but it has more nutrients than sandy soil and it also offers better drainage.

Clay Soil

A kind of material that occurs naturally and consists of very fine grained material with very less air spaces, that is the reason it is difficult to work with since the drainage in this soil is low, most of the time there is a chance of water logging and harm to the roots of the plant.

Loamy Soil

Texture is gritty and retains water very easily, yet the drainage is well.

Peaty Soil

Basically formed by the accumulation of dead and decayed organic matter, it naturally contains much more organic matter than most of the soils.

Chalky Soil

Fertility of this kind of soil depends on the depth of the soil that is on the bed of chalk.

Soil Horizon

A specific layer in the soil which measures parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath.

Main Horizons

The following horizons are listed by their position from top to bottom within the soil profile. Soil generally consists of visually and texturally distinct layers, which can be summarized as follows from top to bottom:O) Organic matterLitter layer of plant residues in relatively undecomposed form. A) Surface soilLayer of mineral soil with most organic matter accumulation and soil life. B) SubsoilLayer of alteration below an "E" or "A" horizon. This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation. C) SubstratumLayer of unconsolidated soil parent material. This layer may accumulate the more soluble compounds that bypass the "B" horizon.

O Horizon

The “O” stands for Organic, with this surface layer being dominated by the presence of large amounts of organic material in varying stages of decomposition.

P Horizon

These horizons are also heavily organic, but are distinct from O Horizons in that they form under waterlogged conditions. The “P” designation comes from their common name, peats. They may be divided into P1 and P2 in the same way as O Horizons.

A Horizon

The A Horizon is the top layer of the soil horizon. The technical definition of an A Horizon may vary, but it is most commonly described in terms relative to deeper layers.

B Horizon

B Horizons are commonly referred to as ‘subsoil’, and consist of mineral layers which may contain concentrations of clay or minerals such as iron or aluminium, or organic material.

E Horizon

“E” being short for eluviated has been significantly leached of its mineral and/or organic content, leaving a pale layer largely composed of silicates.

C Horizon

C Horizons are simply named so because they come ‘after’ A and B within the soil profile. These layers are little affected by soil forming processes, and their lack of pedological development is one of their defining attributes.

D Horizon

Refer to ‘any soil material below the solum that is unlike the solum in general character, is not C horizon, and cannot be given reliable designation

R Horizon

Unlike the above layers, R horizons largely comprise continuous masses (as opposed to boulders) of hard rock that cannot be excavated by hand.

Soil Erosion

The removal of soil by normal earth processes of wind and water, as well as human activities such as agriculture.

Types:

Rill and gully erosion, one of the most common caused by water, occurs when water from a heavy rainfall does not fully infiltrate the ground. A portion becomes runoff, and flows downhill along the steepest gradient. This flow starts as diffuse overland flow, or just a thin sheet of water moving over the ground surface, but due to small differences in the land such as vegetation, it begins to flow in small channels, or rills, where there is the least resistance. As more water flows into a rill, it is eroded at an even faster rate, increasing in size as many small rills converge to form gullies. This type of erosion destabilizes the land surface and carries soil away as waterborn sediment.

Wind erosion is equally damaging because it "physically removes the lighter, less dense soil constituents such as organic matter, clays, and silts." It can carry away the topsoil as airborn dust that can travel great distances.

Images of a river near Richmond, Indiana before and after a large rainfall and flooding event. Nearly 15 feet of bank have been carried away by water erosion in just a few days.