Soil
The top layer of the Earth's surface that supports plant growth. Different types of soil have varying fertility levels and are suitable for different crops.

Soil Profile
A soil profile is a vertical cross-section of the soil, displaying the various layers, or horizons, that make up the soil. Each layer has distinct characteristics, including color, texture, composition, and structure, offering insights into the soil's formation, fertility, and ability to support plant life. The soil profile typically consists of several horizons:

a. O Horizon (Organic Layer): The topmost layer primarily composed of organic matter such as decomposed leaves and plant material. This layer is rich in nutrients and supports the growth of vegetation.
b. A Horizon (Topsoil): Beneath the O horizon lies the topsoil, which is a crucial layer for plant growth. It contains a mix of organic material and mineral particles. Topsoil is dark in color due to its high organic content and is rich in nutrients, making it ideal for agriculture and gardening.
c. E Horizon (Eluviation Layer): Also known as the leaching layer, this horizon is characterized by the removal or leaching of minerals and nutrients due to water percolation. It often appears lighter in color than the layers above and below it.
d. B Horizon (Subsoil): The subsoil contains minerals and nutrients leached from the upper layers. This horizon accumulates minerals like iron, aluminum, and clay, giving it a different texture and color compared to the topsoil.
e. C Horizon (Parent Material): Comprising partially disintegrated or weathered rock, this layer serves as the source of mineral elements for the upper horizons. The C horizon directly influences the soil's composition and properties.
f. R Horizon (Bedrock): The unweathered rock layer at the bottom of the soil profile. Plant roots cannot penetrate this layer, as it is solid rock.

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Soil Erosion
The literal meaning of 'soil erosion' is wearing away of soil. Soil ero- sion is defined as the movement of soil components, especially surface- litter and top soil from one place to another. Soil erosion results in the loss of fertility because it is the top soil layer which is fertile. If we look at the world situation, we find that one third of the world's cropland is getting eroded. Two thirds of the seriously degraded lands lie in Asia and Africa.

Soil erosion is basically of two types based upon the cause of erosion:

a. Normal erosion or geologic erosion:
caused by the gradual removal of top soil by natural processes which bring an equilibrium between physical, biological and hydrological activities and maintain a natural balance between erosion and renewal.
b. Accelerated erosion:
This is mainly caused by anthropogenic (man-made) activities and the rate of erosion is much faster than the rate of formation of soil. Overgrazing, deforestation and mining are some important activities causing accelerated erosion.

Climate Agents
Water and wind are the climatic agents of soil erosion. Water affects soil erosion in the form of torrential rains, rapid flow of water along slopes, run-off, wave action and melting and movement of snow.

Wind induced soil erosion is of the following types:
• Saltation: This occurs under the influence of direct pressure of stormy wind and the soil particles of 1-1.5 mm diameter move up in vertical direction.
• Suspemsion: When there is rainfall and rapidly running water produces finger-shaped grooves or rills over the area, it is called rill erosion.
• Gully erosion: Here fine soil particles (less than 1 mm dia) which are suspended in the alr are kicked up and taken away to distant places.
• Surface creep: Here larger particles (5-10 mm diameter) creep over the soil surface along with wind.
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Biotic agent
Excessive grazing, mining and deforestation are the major biotic agents responsible for soil erosion. Due to these processes the top soil is disturbed or rendered devoid of vegetation cover. So the land is directly exposed to the action of various physical forces facilitating erosion. Overgrazing accounts for 35% of the world's soil erosion while deforestation is responsible for 30% of the earth's seriously eroded lands. Unsustainable methods of farming cause 28% of soil erosion.
Deforestation without reforestation, overgrazing by cattle, surface mining without land reclamation, irrigation techniques that lead to salt build-up, water-logged soil, farming on land with unsuitable terrain, soil compaction by agricultural machinery, action of cattle trarn pling etc make the top soil vulnerable to erosion.

Land Degradation

How To conserve land?

• Conservational till farming: In traditional method the land is ploughed and the soil IS broken up and smoothed to make a planting surface. However, this disturbs the soil and makes it susceptible to erosion when fallow (i.e. without crop cover). Conservational till farm- ing, popularly known as no-till-farming causes minimum disturbance to the top soil. Here special tillers break up and loosen the subsurface soil without turning over the topsoil. The tilling machines make slits in the unploughed soil and inject seeds, fertilizers, herbicides and a little water m the slit, so that the seed germinates and the crop grows successfully without competition with weeds.

• Contour farming: n gentle slopes, crops are grown in rows across, rather than up and down, a practice known as contour farming. Each row planted horizontally along the slope of the land acts as a small dam to help hold soil and slow down loss of soil through run-off water.

• Terracing: It is used on still steeper slopes are converted into a series of broad terraces which run across the contour. Terracing retains water for crops at all levels and cuts down soil erosion by controlling run off. In high rainfall areas, ditches are also provided behind the terrace to permit adequate drainage.