By David Okul
Soil is the uppermost layer of earth’s crust, which supports growth of plants. It is a complex mixture of
- mineral particles (formed from rocks),
- humus (organic material formed from decaying plant remains),
- mineral salts,
- water,
- air, and
- Living organisms (larger ones like earthworms and insects and microscopic ones like the bacteria and fungi).
Soil is a renewable as well as non-renewable resource. Soil is renewable because its productivity can be maintained with fertilizers and manures rich in humus.
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If the soil has been removed from a certain place by erosion, it is practically non-renewable because formation of new soil may take hundreds and thousands of years. Let us discuss erosion as it is a major threat to soil resource.
Soil Erosion
Erosion literally means “to wear away”. You might have noticed during the dry season, when wind blows it carries away sand and soil particles from one place to another. Similarly flowing water removes some amount of soil along with it. This removal of top layers of soil by wind and water is called soil erosion. You know that top layers of soil contain humus and mineral salts, which are vital for the growth of plants. Thus, erosion causes a significant loss of humus and nutrients, and decreases the fertility of soil.
Causes of soil Erosion
Now we shall discuss the causes of soil erosion. There are several causes of soil erosion, these include:
(a) Natural causes; and
(b) Anthropogenic causes (human generated causes)
(a) Natural Causes of Soil Erosion
Erosion of soil takes places due to the effect of natural agents like wind and water. High speed winds over lands, which have no vegetation, carry away the loose top soil. Similarly in areas with no or very little vegetation, the pouring raindrops carry away the soil.
(b) Anthropogenic/ man-made Causes of Soil Erosion
Besides the natural agents, there are some human activities, which cause soil erosion. Let us know about them.
- Deforestation: If the forests are cut down for timber, or for farming purposes, then the soil is no longer protected from the effect of falling rains. Consequently, the top soil is washed away into the rivers and oceans.
- Poor farming methods: Improper tillage and failure to replace humus after successive crops and burning the stubble of weeds reduce the water-holding capacity of the soil. So the soil becomes dry and can be blown away as dust.
- Overgrazing: Overgrazing by flocks of cattle, buffaloes, goats and sheep leave very little plant-cover on the soil. Their hooves make the soil dry and soil can be blown away easily.
What are the possible causes of soil erosion in your area?
Conservation of Soil
In the previous section we learnt about the various causes of soil erosion. Soil loses its fertility due to erosion. So we need to conserve the soil. Soil conservation means checking soil erosion and improving soil fertility by adopting various methods. Let us know some of these methods.
- Maintenance of soil fertility: The fertility can be maintained by adding manure and fertilizers regularly as well as by rotation of crop.
- Control on grazing: Grazing should be allowed only on the areas meant for it and not on agricultural land.
- Reforestation: Planting of trees and vegetation reduces soil erosion by both water and wind.
- Terracing: Dividing a slope into several flat fields to control rapid run of water. It is practiced mostly in hilly areas.
- Contour ploughing: Ploughing at right angles to the slope allows the furrows to trap water and check soil erosion by rain water.
- Building gabions
Concluding Remarks
David Okul is an environmental management professional with over 10 years experience on donor projects, conservation, forestry, ecotourism, and community-based natural resources management. When not working on environmental projects, I spend my time writing for Silvica on a variety of topics. The view in this blog are personal and do not represent the organizations that he is associated with.
