(a) Explain the term soil erosion (b) Write notes on soil erosion under the following headings: (i) causes (ii) effects (iii) methods of prevention

Answer Details

(a) Meaning of soil erosion

Soil erosion is the wearing away, loosening and removal of the top (surface) layer of the soil from one place to another by natural agents such as running water, wind, ice or waves, and often accelerated by human activities. It is most serious when the fertile topsoil is stripped away faster than it can be replaced.

(b) Notes on soil erosion

(i) Causes

• Heavy rainfall and steep slopes, which give fast-flowing run-off that carries soil away (sheet, rill and gully erosion).
• Removal of vegetation cover through deforestation, bush burning and overgrazing, leaving the soil bare and exposed.
• Poor farming methods such as ploughing up and down slopes, continuous cropping and shifting cultivation on fragile land.
• Strong winds in dry, bare areas that blow away loose soil particles.

(ii) Effects

• Loss of soil fertility as the nutrient-rich topsoil is removed, reducing crop yields.
• Formation of gullies and badlands that destroy farmland, roads and buildings.
• Silting of rivers, dams and reservoirs by the eroded material, causing flooding and shortening the life of dams.
• Desertification and migration as land becomes unproductive, forcing people to move away.

(iii) Methods of prevention

• Afforestation and re-vegetation to bind the soil with roots and break the force of rain and wind.
• Contour ploughing, terracing and strip cropping on slopes to slow down run-off.
• Cover cropping, mulching and crop rotation to keep the soil covered and maintain fertility.
• Building drainage channels, check dams and planting wind breaks (shelter belts), and controlling bush burning and overgrazing.