Soil Erosion and Degradation: Types, Causes, and Prevention
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Soil Erosion and Degradation: Types, Causes, and Prevention
Geography for Civil Services
What are soil erosion and soil degradation? Although soil erosion is a natural process, human activities over the past decades have greatly accelerated it. In fact, according to the UNESCO, land degradation is undermining the well-being of two-fifths of humanity, driving species extinct and intensifying climate change.
Problems of Indian soils:
- Soil degradation
- Soil erosion
- Deficiency infertility
- Salinity and alkalinity
- Soil degradation is the decline in soil quality caused by its improper use, usually for agricultural, pastoral, industrial, or urban purposes.
- Soil degradation is the main factor leading to the depleting soil resource base in India.
- The degree of soil degradation varies from place to place according to the topography, wind velocity, and amount of rainfall.
- Soil erosion is the removal of topsoil (which has most of the nutrients necessary for a plant’s growth) by agents like wind and water.
- Over-dependence on agriculture and improper land management is also the leading cause.
- Wind and water are powerful agents of soil erosion because of their ability to remove soil and transport it.
i. Soil erosion by Water:
- Water erosion takes place mainly in the form of sheet and gully erosion.
- When the entire top sheet of soil is washed away by heavy rainwater, leaving behind a barren rock, it is called sheet erosion.
- Sheet erosion attacks a large area of topsoil and renders the land almost unfit for cultivation.
- Gully erosion is the removal of soil along drainage lines by surface water runoff.
- Gully erosion is common on steep slopes.
- Gullies deepen with rainfall, cut the agricultural lands into small fragments, and make them unfit for cultivation.
- When a gully bed is eroded further, the bed gradually deepens and flattens out and a ravine is formed like in the Chambal basin.
ii. Soil erosion by Wind:
- Wind erosion or Aeolian erosion is quite significant in arid and semi-arid regions.
- Winds usually blow at high speeds in deserts due to the absence of trees.
- Suspension, saltation, and surface creep are the three types of soil movement which occur during wind erosion.
- While soil can be blown away at virtually any height, the majority (over 93%) of soil movement takes place at or below one meter.
Factors affecting Soil Erosion:
- Intensity and duration of rainfall
- Wind speed
- Nature of soil and the physiography
- Strong winds in dry areas
- Faulty methods of agriculture
- Diversion of natural drainage courses
- The wrong orientation of roads and railways, embankments and bridges.
Effects of Soil Erosion:
- Erosion of fertile topsoil.
- Loss of mineral nutrients because of flooding and leaching.
- Lowering of Groundwater level
- Decrease in soil moisture.
- Increased frequency and intensity of floods and drought.
- Rivers, canals, and tanks are silted and their water holding capacity decreases.
- Soil conservation is the prevention of soil from erosion or reduced fertility caused by overuse, acidification, salinization, or other chemical soil contamination.
Some methods of soil conservations are:
- Checking Overgrazing
- Constructing dams
- Changing agricultural practices
Methods of soil Conservation:
- prevention of forest destruction along with growing new forests or increase the area under forests.
- By stopping indiscriminate felling of trees.
2. Checking Overgrazing:
- By creating separate grazing grounds and producing larger quantities of fodder.
- By educating villagers about the consequences.
3. Constructing dams:
- Dam construction checks the speed of water and saves soil from erosion.
- But indiscriminate dam construction can worsen the condition by creating floods and landslides like it happens in the Himalayan region.
4. Changing agricultural practices:
- Crop rotation
- Strip cropping
- Contour Ploughing
- Terracing and contour bunding
- Checking Shifting cultivation
1. Crop rotation:
- Crop rotation is a practice in which a different crop is cultivated on a piece of land each year.
- Sowing the same crop leads to exhaustion of certain nutrients in the soil making it infertile.
- Crop rotation helps to conserve soil fertility as different crops require different nutrients from the soil.
2. Strip Cropping:
- Crops are cultivated in alternate strips, parallel to one another. Some strips may be allowed to lie fallow while in others different crops may be sown.
- Various crops are harvested at different intervals. This ensures that at no time of the year the entire area is left bare or exposed.
- The tall-growing crops act as windbreaks and the strips which are often parallel to the contours help in increasing water absorption by the soil by slowing down runoff.
3. Contour Ploughing
- If ploughing is done at right angles to the hill slope, following the natural contours of the hill, the ridges and furrows break the flow of water down the hill.
- This prevents excessive soil loss as gullies are less likely to develop and also reduce run-off so that plants receive more water.
4. Terracing and Contour bunding
- In terracing, a number of terraces are cut along the hill slope.
- These are made on steep slopes so that flat surfaces are available to grow crops. They can reduce surface run-off and soil erosion.
- Contour bunding involves the construction of banks along the contours.
- Terracing and contour bunding divide the hill slope into numerous small slopes, check the flow of water, promote absorption of water by soil and save soil from erosion.
- The bare ground (topsoil) between plants is covered with a protective layer of organic matter like grass clippings, straw, etc.
- Protects the soil from erosion.
- It helps to retain soil moisture.
- Reduces compaction from the impact of heavy rains.
- Conserves moisture, reducing the need for frequent watering.
6. Checking Shifting cultivation
- Checking and reducing shifting cultivation by persuading the tribal people to switch over to settled agriculture is a very effective method of soil conservation.
- This can be done by making arrangements for their resettlement which involves the provision of residential accommodation, agricultural implements, seeds, manures, cattle, and reclaimed land.
- Integrated land-use planning seems to be the best technique for proper soil conservation.
- Lands should be classified according to their capability.
- land use maps should be prepared and lands should be put to the right uses.
- The final responsibility for achieving the conservation of land will rest on the people who operate on it and receive the benefits.