SOIL EROSION

SOIL EROSION   

This is the removal of fertile top soil by water or wind.

Effects of soil erosion to the farmer:   

• The top soil that is being washed away contains most nutrients, organic matter and soil organisms there fore crop production will be reduced.
• Erosion leaves behind a hard stony ground which is difficult to cultivate.
• As erosion moves the soil from place o place it destabilizes the soil profile.
• Erosion may remove infertile soil from one place and depost it on top of fertile soil elsewhere reducing crop production in that area.
• Erosion can cause crops to be washed away.
• Some crops at the bottom of the slopes are covered with soil that has been removed from the soil.
• When it is gulley erosion, it cuts the field into irregular pieces and this will interfere with movement of animals, farmer and use of machinery.

The main agents are water and wind. Wind erosion is common in semi arid areas where there is bore ground (without vegetation) and the winds are strong.

Factors that affect water erosion.

• Rain fall intensity (heaviness)

Heavy rain even if for a short period will cause more erosion than a light shower that way go on for a long time.

• Topography

The steeper the slope, the greater the speed of surface water flow therefore the more intense erosion will be.

• Type of soil

Sandy soil particles do not stick together therefore can easily be washed away by running water.  Clay particles stick together so will offer some resistance to erosion.

• Type of vegetation

A bare ground without vegetation will easily be eroded. Creetiping plants, pasture, and bush fallow offer a very good ground cover and here will be no erosion. The forest canopy will also protect the ground from erosion. Crops that grow upright especially when there are widely spaced like cassava leaves.

• Farming practices

When the farmer digs up and down a slope or carries out bush burning, overgrazing or over cultivation of land, soil erosion will easily occur.  Good practices like mulching, crop rotation, planning e.t.c. will discourage soil erosion.

Types of erosion

• Rain drop / splash erosion

This results from the direct impact of rain drops on bare ground. The bigger the drops, the greater the erosion will be .Drops of rain will cause soil particles scatter and will form a muddy solution that will seal off all pore spaces and prevent further infiltration of water into the soil, instead it  will flow as  a stream over the surface – surface water flow. This will lead to the second type of erosion sheet erosion.

• Rill erosion

Soil removal will lead to formation of small, clearly cut channels called rills that can easily be seen. Rills are usually formed where rain comes as a form and soil particles can not hold together.

They can easily be removed through cultivation.

• Gulley erosion                                                                                                                                                

Here wide and deep irregular tunnels are cut across the field and they carry a lot of water. Very large volumes of soils are removed form the field and will interfere with movement of man, livestock and machinery. Galleys can not be removed by simple cultivation and require mechanical method e.g. Barragos.