Soil erosion is defined as the "accelerated removal of soil, typically with catastrophic
consequences due to improper land use" (Wilhelmy, 1992, p. 165).
Two main types are distinguished:
- Water erosion
- Wind erosion
Both types of erosion depend directly on the size and weight of soil particles, as
well as the energy
inherent in water or wind, and the terrain surface and slope.
Methods to reduce water erosion include:
- Contour ploughing: Sloping fields
are ploughed parallel to the contour lines, thereby reducing
surface runoff.
- Strip farming: Fields are divided
into several strips, alternating between cultivated and fallow
areas.
- Terracing: An expensive method to
protect erosion-prone land from washouts; terraces are
constructed on slopes.
- Crop rotation: Alternating between
cereal (straw) crops and broadleaf crops to improve soil
quality and provide protection (Bender, 1995, p. 397).
- Conversion to grassland or forest:
Applied in areas with a high risk of erosion.
Methods to reduce wind erosion include:
- Dry farming: Fallow fields are ploughed
before the onset of rainfall to allow better water
infiltration. After rainfall, the fields are harrowed. This destroys soil capillaries, reducing
evaporation.
- Stubble mulching: In this method,
crop stubble is left standing in the fields, serving as a
windbreak (Bender, 1995, p. 397).
- Minimum tillage: This is an extension
of stubble mulching. Seeds are sown into stubble fields
by scoring the soil, placing the seed in the furrow, and immediately closing it again (Allkämper,
1996, p. 18).
- Windbreaks or shelterbelts are rows
of trees, shrubs, or other vegetation planted to reduce wind
speed and protect soil, crops, and livestock from wind erosion and damage. They are a key
method for controlling wind erosion.
Key Functions:
- Reduce Wind Speed: They disrupt and
slow down wind flow, decreasing its erosive
energy.
- Trap Windblown Soil: They act as
physical barriers that capture soil particles carried by
the wind.
- Microclimate Improvement: They can
reduce evaporation, moderate temperatures, and
increase humidity in sheltered areas.
- Provide Habitat: They offer shelter
and food for wildlife and beneficial insects.
Design Considerations:
Orientation: Planted perpendicular to the prevailing wind
direction. Density: Optimal porosity (not too dense, not too open) is crucial for effective wind
reduction without creating turbulence. Height and Length: Protection extends downwind for
a distance of about 10-20 times the height of the windbreak.
