Resources and Development
Soil erosion and conservation
Explain how soil is eroded and how farmers save it.
What is soil erosion? The soil cover is stripped away and washed down. Soil forms and wears away at the same time, and usually the two stay in balance. People upset that balance by cutting forests, overgrazing, building and mining. Nature erodes too, through wind, glaciers and water.
Three kinds of erosion.
- Gully erosion: running water cuts deep channels in clayey soil. The land becomes bad land, unfit for farming. In the Chambal basin such land is called ravines.
- Sheet erosion: water flows as a thin sheet over a large slope and carries away the top soil.
- Wind erosion: the wind carries off loose, dry soil.
Picture it: throw a bucket of water down a field and the soil runs off; switch on a big fan and the dry soil blows away.
Wrong ploughing. Ploughing up and down a slope makes channels for water to rush down, carrying soil with it. Contour ploughing, along the slope's level lines, slows the water.
Terraces. Steps are cut into the slope, making flat strips of land that hold the soil. Terrace farming is well developed in the western and central Himalayas.
Strips and shelter belts.
- Strip cropping: big fields are split into strips, with grass left growing between the crops to break the force of the wind.
- Shelter belts: rows of trees that shelter the land. They have helped hold sand dunes in place and steady the desert in western India.
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