Recognize Eroded Areas

Farming activities have a direct impact on the environment. This may be a positive or negative one depending on how pro-active and conservation-conscious the farmer is.

The following are examples of “poor farming practices” that have a negative effect on the environment:

• Overgrazing of animals.
• Poor irrigation.
• Inappropriate farming techniques (i.e. deep ploughing 2 to3 times per year to produce annual crops).
• Intensive farming practices – the lack of crop rotation.
• Planting crops down the contour instead of along it.
• Destruction of tree and plant cover.

Soil Erosion

Soil erosion is a serious problem throughout the world. South Africa is a relatively dry country compared to many other countries. Poor soil management results in soil loss from arable lands, into rivers, which eventually finds its way into the ocean.

Soil erosion is caused by water and/or wind.

Water Erosion

The main cause of soil erosion is water. When a drop of water hits soil with no plant cover, it impacts the soil is like a bullet. This action causes the soil grains to loosen. The loose soil grains are suspended in the water and run off with the water.

Nutritious topsoil is always first to be removed as it is the top layer of soil. Without topsoil, plants cannot grow, and the land becomes desert-like. Without plant cover, the effect of water is multiplied, and the result is desertification, meaning that the area literally becomes a desert.

Water erosion also affects downstream areas, causing flooding and silting up dams because of the suspended soil particles.

The flow of the water causes the formation of channels, and eventually dongas and gullies. Channels occur on steep slopes because of the irregularities in the land. Water finds hollows that run into one another and slowly deepen to form miniature dongas.

Dongas usually occur near the bottom of slopes and are caused by runoff of water and soil-forming a deep channel or gully. A deep channel eventually opens at the bottom end of the slope and slowly works its way from the channel, deepening and widening it, until a donga is formed.

Wind erodes the soil by blowing away loose soil particles if the soil is left bare. Wind erosion is not a big issue in citrus production but is prevalent in arid areas, and around animal watering holes.

Preventing Soil Erosion

Soil erosion can be prevented by employing the following measures:

• Arable land should not be left bare.
• Make and use contours when ploughing and planting.
• Plant windbreaks.
• Ensure the soil is rich in humus.
• Allow indigenous plants to grow along rivers and in gullies.
• Conserve wetlands, grasslands and forests.
• Perform minimum or no-tillage.
• Encourage water infiltration by improving the soil structure.
• Reduce water runoff.
• Ensure there is a protective plant cover.
• Plant ground covers to stabilise the soil.
• Build gabions and install shade cloth barriers in gullies to prevent soil from washing away.
• Mulch soil to prevent dust particles from blowing away.

Although weeds compete with citrus trees for water and food and are therefore controlled in an orchard, a good grass covering provides protection against excessive run-off and the resultant soil erosion. Careful management of irrigation also contributes to controlling soil erosion.

The formation of gullies and dongas can be prevented by:

• Diverting waterways to reduce the intense water flow
• Planting grass in waterways to prevent soil erosion

Once a gully has formed, the land can be rehabilitated by shoring it up with old tree trunks, etc.

Remember

Soil erosion is caused by water or wind.

Gullies and dongas are formed as a result of soil erosion.

Soil erosion can be prevented and controlled by maintaining a grass cover in orchards and controlling irrigation by managing irrigation to prevent excessive runoff.

Dongas and gullies can be rehabilitated by diverting waterways and by shoring them up.