मृदा क्षरण और कृषि पर इसका असर
Soil erosion is a major problem in Agriculture. Tonnes of soil are lost from fields every year. This is not only reduces crop production, but also the eroded soil acts as a pollutant to rivers, lakes and other water systems.
Soil is the top layer of the earth’s surface that is capable of sustaining life. Therefore, soil is very important to farmers, who depend on soil to provide abundant, healthy crops each year.
One major problem in agriculture is soil erosion. Soil erosion is the deterioration or detachment of soil particles from one place to another place by the action of different medium in a given site. Wind, water, ice, animals, and the use of tools by man are usually the main causes of soil erosion.
Erosion is a natural process which usually does not cause any major problems. It becomes a problematic when anthropogenic activities are much faster than under normal conditions.
Worldwide, farmers are losing an estimated 24 billion tonnes of top soil every year. Topsoil contains most of the soil’s nutrients, organic matter, and pesticides which are necessary for crop cultivation. Soil erosion causes these substances to move also. Therefore, fertilizers and organic matter must be added in an attempt to restore the soil to its original composition.
Location of Soil Erosion:
The severity of soil erosion may vary from place to place. Wind and water are the main causes of soil erosion. The plant cover and size of soil particles are two main factors that associated with erosion. Wind erosion is a more common problem in dry, windy regions, with a smooth, flat terrain. Water erosion is a problem in wet regions with a sloping or hilly terrain.
Soil erosion is caused by natural processes as well as by human activities. The natural processes can be divided into:
1. Geological Erosion:
Geological soil erosion is a natural process that tends to bring the earth's surface to a uniform level. This erosion occur continuous and slow rate. It is mainly caused by rainfall, runoff, slope, wind velocity and gravitational force. This erosion is also called natural erosion. In this erosion, soil development is more than the soil erosion.
2. Accelerated Erosion:
Under cultivation, the land experiences a lot of pressure from outside and consequently the balance between vegetation cover and climate is disturbed. Thus, removal of surface soil by natural agencies takes place at a faster rate than it can be built up by soil forming process.
Erosion occurring under these conditions is referred to as accelerated erosion. Its rate and magnitude are higher than those in normal geological erosion.
There are mainly two types of soil erosion:
1. Water Erosion
Removal of topsoil by water is called water erosion. It takes place in the following ways:
- Splash erosion: it is caused by beating action of raindrops. This is the first stage of water erosion. In this erosion soil particles detach and dispersed due to force rain drop.
- Sheet Erosion: The removal of the entire topsoil as a result of heavy rains is called sheet erosion. It is also known as farmer’s death due to loss of productive layer of soil. This erosion is mostly occurring in low organic matter content soil and poor vegetative area.
- Rill Erosion: Runoff water moves across the soil forming small streams. The topsoil is removed only in these rills formed by the water streams. These rills can be easily removed by ploughing.
- Gully Erosion: The advance stage of rill erosion is known as gully erosion. Deep depressions called the gullies are formed by swiftly moving waters causing soil erosion by them. These gullies cannot be removed by normal tillage operations.
2. Wind Erosion:
The other cause for erosion is wind. It is more in areas where there is less or no vegetation covering the land. The fast moving wind moves the fine particles to other places. The wind laden with fine sand deposits the latter and forms sand dunes. Shifting sand dunes are common in dry areas of Rajasthan, Gujarat and Madhya Pradesh.
Major causes of soil erosion
The major causes of soil erosion are as follows:
1. Excessive Rain fall:
Due to excessive rain fall and poor water holding capacity of soil, water moves on the surface is called runoff and it removes top fertile soil.
2. Human activities: Human activities accelerate disappearance of protective cover of natural vegetation and cause soil erosion. It is artificial erosion.
3. Over grazing: Over grazing leads to the absence of ground-vegetation, cause gradual depletion of soil organisms, and cause soil erosion.
4. Deforestation: It causes soil erosion by rapid rain fall and the flow of wind.
5. Minute Activities: Such mining activities such as open cast mining and underground mining lead to soil erosion.
- Open cast Mining: One cast mining helps in the complete removal of soil and leads to the destruction of the total land area, loss of productive area and soil erosion is caused.
- Underground Mining: Underground mining leads to the whole area a depression and it becomes a waste land. It also causes run off acids which crude soil. The toxic chemicals from solid wastes are absorbed by soil and may kill plants and animals.
6. Shifting cultivation: As forests are slashed and burnt it reduces humus content and decrease water holding capacity of soil. So cultivators move to another patch of forests for fresh cultivation. The resulting exposure of soil to rain and wind causes drastic soil erosion.
Effects of Soil Erosion on agriculture:
- Loss of fertile top soil
- Loss of rain water
- Loss of plant nutrients from the soil
- Accumulation of sand and other unproductive course materials on productive soil
- Silting of reservoirs, lake, and irrigation channel
- Fragmentation of land mainly by gully erosion
- Increase flooding condition
- Adverse effect on human health and crop yield
- Destroy soil structure and other physical problems
- Loss of biodiversity
Management of Soil Erosion:
- Growing of cover crops like cowpea, moong, urd etc which protect from direct effect of raindrops.
- Addition of organic matter into the soil that bind soil particles and reduce soil erosion
- Afforestation decrease runoff and prevent soil loss
- Levelling of land should be maintain
- Growing of crops across the slope
- Growing of wind break and shelter belts
- Use of agroforestry system
- Do not fallow the land
- Make gully structure to check water steam like dam, water spill structure etc.
- Adopt contour cultivation in hilly or sloppy area
Authors:
Dr. Arbind Kumar Gupta
Assistant Professor, Department of Soil Science,
College of Forestry, BUAT, Banda-210001
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