Soil erosion is the wearing away of land surface by the action of natural agencies, such as water and wind. It involves separation of soil particles by the action of these natural forces. Erosion can also be caused by living organisms such as burrowing animals and is referred to as bio-erosion.
Simply we can say that soil erosion is the displacement of top layer of the soil. It badly affect all landforms. In agriculture, soil erosion, displace the top soil of field which highly affect the farming activities because topsoil contains most fertile soil and nutrient rich materials.
Soil erosion weather it is by water, wind or any other physical forces, involves three different actions soil detachment, movement and deposition.
It is removal of the surface soil from any area denuded of its natural protective cover as a result of human and animal interference.
Erosion extensively occurs in poorly aggregated soil and in a higher percentage of silt and very fine sand. Erosion increase when soil remains bare or without vegetation.
At normal geological pace, nature requires 1,000 years to build up 2.5 cm of top soil, but wrong forming methods may take only a few years to erode it from the lands of average slope.
It is impossible to stop soil erosion completely, but can be minimised. Techniques to control soil erosion usually result in maintaining or increasing soil productivity also.
Types of soil erosion
Removal of a fairly uniform layer of surface soil by the action of rainfall and run-off water. This sheet erosion depends on the amount of runoff water and erodability of soil.
Sheet erosion is generally occurs in the foothills of Himalaya, eastern and western Ghats. This type of erosion, though extremely harmful to the land, is usually so slow that the former is not conscious of its existence.
Its existence, however, can be detected by the muddy colour of the run-off arising from the fields.
This is the removal of surface soil by running water, with the formation of narrow shallow channels that can be levelled or smoothed out completely by normal cultivation.
This type of soil erosion may be regarded as a transition stage between sheet and gully erosion. Rill erosion occur when running water forms channel in the slope.
When rill erosion is neglected, the tiny grooves develop into wider and deeper channel known as gully erosion. Gully erosion is an advanced stage of rill erosion.
They cut up large fields into small fragments and in course of time, make them unfit for cultivation. This gully erosion leads to the formation of bad land topography.
Gully erosion occur when running concentrated water flows strongly enough to detach soil particles. This type of erosion highly affect the soil productivity.
The development of gully occurs due to following four step :-
1.) Formation stage – With channel erosion by a download scour of the surface soil.
2.) Development stage – Consisting of upstream movement of the gully head and enlargement of the gully in width and depth.
3.) Healing stage – Beginning with the growing of vegetation in the gully.
4.) Stabilization stage – The gully reaches a stable gradient, gully walls reaches a stable slope, and vegetation cover spreads over the gully surface.
Classification: Gully erosion
It is classified in four types on the basis of their size
Very small gullies – Deep — upto 3 m, width — not greater than 18 m.
Small gullies – Deep — upto 3 m, width — >18 m (between 8 to 15%.
Medium gullies – Deep — between 3 to 9 m, Width — >18 m, width — between 8 to 15%.
Deep and narrow gullies – Deep — 9 m, width — varies mostly steep or even vertical with intricate and active branch gullies.
Stream Channel Erosion
It is caused by river, stream also called chos, cutting their banks and adjoining fields. This erosion occurs at the lower end of stream tributaries and to streams that have nearly continuous flow and relatively flat gradient. Stream but erode either by run-off flowing over the side of the stream bank, or by scouring or undercutting.
Raindrop Splash esosion
The soil splash caused by the impact of falling rain drops. Splash erosion result from the bombardment of the soil erosion because of rain drops. Because the rain drop behave like a little bomb when falling in the soil.
There are four factors that determines the rate of rain drop erosion namely :
(1) Climatic (mostly rainfall and temperature),
(2) Soil – its inherent resistance to dispersion and its infiltration rate,
(3) Topography particularly steepness and length of slope, and
(4) Vegetative cover – either living or the residues of dead vegetation.
Causes of soil erosion
The major causes affecting soil erosion are :
Wind has caused an accumulation of eroded particles. Movement of soil particles is caused by wind forces exerted against or parallel to the surface of ground.
After such movement is started, the soil particles are carried by the wind in three types namely saltation, suspension and surface creep.
This is a process of soil movement in a series of bounces or jumps.Soil particles having sizes ranging from 0.05 to 0.5 mm generally move in this process.
It is caused by the direct pressure of wind on soil particles. After being pushed along the ground surface by the wind, the particles leap almost vertically in the first stage stage.
Very fine soil particles, less than 0.1 mm in diameter, are carried into suspension, being kicked up into the air by the action of particles in saltation.
The movement of fine dust in suspension is completely governed by the characteristics movement of the wind.
Soil particles, larger than 0.5 mm in diameter but smaller than 1.0 mm, are too heavy to be moved in saltation, and are pushed along the surface by the impact of particles in saltation to form a surface creep.
The soil moved in saltation and surface creep usually remains within the eroded area, especially when erosive winds are from different directions.
This is the very important agents for soil erosion as compared to other. It soil erosion starts due to water when raindrops strike bare soil peds and clods, resulting the finger particles to move with the flowing water as suspended sediments.
The soil along with water moves downhill, scouring channels along the way. Each subsequent rain erodes further amounts of soil until erosion has transformed the area into barren soil.
(3) Human Activities
Human activities such as deforestation, grazing etc destroying our earth surface for self benefit. It is increasing day by day. There are three main point for caring:
Most of farmers graz too many animals such as sheep, ox, cattle, cow or goats on their land. This animals destroy the land surface by eating grass or vegetation.
This leads to the damaging of the soil structure as the level of nutrients is removed and it helps to unbalance the environment.
According to population, market demand is increasing each and every day. To fulfill this issue farmers produce more than vegetable crop continuously.
This constant cultivation of the land reduces the soils ability to produce valuable humus for soil fertility. The soil becomes drier and less fertile as well as it encourages the soil erosion.
The removal of forest trees by cutting and burning for fuel, agricultural use, industrial purposes etc. Due to deforestation, the soil becomes loose and the attraction of soil particles ends. Due to the weakening of the soil, air and
Note :- Soil and water conservation form soil erosion –
Soil and water are valuable natural resources and the source of human support and security. Since economic stability and scientific use of land and water resources can not be separated.
These resources are essential for maintain productivity and decided sustainable healthy environment. So conservation of soil and water resources from soil erosion and others factors are very important for life-support system of our planet.