Soil erosion - Soil Essentials: Managing Your Farm's Primary Asset - page 103

Ground cover
Bare soil is much more prone to erosion than soil with even moderate amounts of
vegetative cover. This cover does not have to be living plants, but dry crop or
pasture stubble or various forms of mulch can also effectively protect soil from
erosion. The important issue is that the plant matter or mulch absorbs the energy
from the raindrops, and prevents soil particles being loosened and displaced. In
areas where earthworms are very active, their castings on the soil surface can also
help protect the underlying soil. Bare soil may be the result of management
practices, or could be the result of wildfires, which may almost completely remove
vegetative cover over large areas, often in steep, highly erodable country. The
quality of ground cover may also be limited by the fertility of the soil, and if
fertility is low, then it may only support sparse vegetation.
Soil management
The quality of land management can have a large effect on how prone the soil is to
erosion. As previously discussed, maintaining at least some vegetative cover on soil
is very helpful. Avoiding soil compaction from heavy stocking rates on wet
paddocks, or excessive trafficking by vehicles or machinery, will help reduce water
runoff and hence erosion. Avoiding long periods of bare cultivated ground when
cropping by replacing fallowing prior to sowing crops with the direct drilling or
stubble mulching methods, will greatly reduce the risk of soil erosion.
Variables affecting wind erosion
Wind speed
As with water, the higher the wind speed, the more energy it has to shift soil, and
again large areas of loose soil are especially at risk if they have no protective plant
cover.
Area of unprotected soil
The greater the exposed area, the more prone it is to erosion by wind. This is
because there is nothing to slow the wind down or dissipate its energy by diverting
it from its path. There is nothing to prevent it from moving soil particles that can
then gain energy and themselves impact on more soil particles, causing mass soil
movement. The wind can then pick up and carry this moving soil until it loses
velocity and the soil is deposited. There are two aspects to this: (1) soil movement
along the surface, and (2) soil movement through the air. It is the larger and
heavier particles that move along the surface, and the lighter particles that move
through the air.