Soil erosion is a major global problem, with 75 billion tons of fertile soil lost annually worldwide. Wind erosion is a significant issue, removing 40% of Pakistan's soil over time. Several factors influence wind erosion, including soil texture, structure, protection by plants, rainfall, and wind force. Methods to control wind erosion include planting shelterbelts, increasing soil organic matter, strip cropping perpendicular to winds, leaving stubble barriers, and reducing tillage. Proper land management is key to reducing the effects of wind on soils.

1. MOHSIN ZAFAR
Lecturer, Soil Science
Faculty of Agriculture, Rawalakot

2. Soil Erosion

3. Soil Erosion Global Problem
• Soil erosion ranks as one of the most serious
environmental problems in the world
• 75 billion tons of fertile soil lost annually around
the world
• Africa, Europe & Australia : 5-10 tons/ha/y
• North, Central & South America: 10-20
tons/ha/y
• Asia: 30 tons/ha/y
• Soils essentially non-renewable as 2.54 cm of
soil estimated to take 200-1000 years to form……
• Annual costs of soil erosion in U.S. estimated
between $30-44 billion in 2002

4. WIND EROSION LOSSES IN
PAKISTAN
• Total area = 79.61 m ha
• Cultivated area = 20.61 m ha
• Forest area = 3.61 m ha
• Area affected by Erosion = 76 %
• Affected by Wind Erosion = 40 %

6. Types of Erosion
• Geological erosion
(natural)
• Accelerated erosion
(because of poor
management)
(Ding Darlington 1947)

7. Natural Systems Also Experience Erosion
 In stable forest ecosystems only 0.004-0.05 tons/ha/y of soil are
lost by erosion
 Forests (on average) require 60% forest cover on landscape to
prevent erosion
 Common along banks of streams and rivers (exacerbated by
cattle grazing)
 Wildfires, landslides and other natural disturbances

8. EROSION
• Erosion is a natural process, accelerated by farming
activity, that removes topsoil, reduces levels of soil
organic matter, and contributes to the breakdown of soil
structure.
• Erosion is a process by which soil is moved from one
area to another. In the geological past, huge volumes of
land surface materials were moved by glaciers.
• At present, the main natural agents of erosion are wind
and water.

9. • Erosion occurs naturally on cropland, forested land, and
in urban areas, but this process can be accelerated by
human activity (such as agriculture, forestry, and urban
development) to levels that cause environmental and
economic problems.

10. WIND STORMS

11. Factors of Wind Erosion
E = f(I, C, K, L, V)
I is the soil erodibility by wind (related to relative amount of
particles > 0.84 mm dia.
C is the local wind erosion climatic factor (product of
average wind velocity and average moisture of soil
surface)
K is the soil surface roughness (expressed in height of
ridges; more roughness increases resistance to wind
erosion)
L is the unprotected width of the field (protection provided
by wind breaks)
V is the equivalent quantity of vegetative cover (includes
quantity, kind, and orientation of vegetative cover

12. Factors Affecting Wind Erosion
Several factors relating to soil, landscape and
climate that affects wind erosion are
• soil texture
• soil structure
• surface relief
• soil protection by plants or plant residues
• rainfall
• wind force.

13. • Erosion works on loosely held soil particles at the soil
surface.
• Silty and very fine sandy soils are particularly vulnerable to
erosion.
• Poorly structured soils whose aggregates (clumps) have
been broken down into fine particles by tillage and other
forces are also easily eroded.
•Surface relief (shape and slope) affects the direction and rate
of erosion. It also affects the location of soil deposition,
because eroded soil tends to accumulate at the base of
slopes and in depressions.

14. • Exposed soils suffer greater erosion than soils well
protected by standing plants or plant residues
• Climate affects erosion mainly through the moisture
conditions of the soil and specific climatic events (wind and
rainstorms).
• Soils are most vulnerable to wind erosion when the soil
surface dries out rapidly during periods of low or no rainfall,
such as the drought during the "dirty thirties" in the prairies
or in early spring when the soil is not protected by
vegetation.
• Wind speed and the length of time the wind blows are
major factors in wind erosion.

15. Causes of Wind Erosion
• Bare, unprotected soil is extremely vulnerable to
wind erosion
• Erosion occurs with strong, turbulent winds
blowing across a soil surface that is smooth,
loose, dry and finely granulated.
• Slightly larger soil particles bounce or roll along
the soil surface.
• Loose particles drift along, bombarding and
dislodging still more particles with the same
effect on clods or growing plants as
sandblasting.

16. Over-grazing by livestock

17. SIGNS OF WIND EROSION
Sometimes erosion is spotted easily in the field.
Common signs of wind erosion include:
• Dust clouds
• Accumulation of soil along fence lines and banks
• Drifted appearance of the soil surface.

18. WIND
EROSION
Rarely produces the catastrophic dust storms
known as the Dust Bowl in the 1930s in the US,
but damages soil like water erosion by removing
organic matter and plant nutrients and by
decreasing soil thickness

19. Wind Erosion
• Both wind and water
behave as fluids, so
processes of erosion
similar
• When the wind force
(function of velocity)
exceeds forces holding
particle in the pedon, it
moves the particle

20. Forms of Wind
Erosion
Saltation: lifting and bouncing of a particle,most
important for particles 0.1 - 0.5 mm dia.
Creep: coarse and very coarse sand grains rolled on
ground surface
Suspension: Lifting of silt- and clay-sized particles
(<0.1 mm) high into the air and can thus be carried
long distances

21. MECHANISM OF SOIL PARTICLE
MIOVEMENT
DETRUSION
EFFLUXION
EXTRUSION
EFFLATION
ABRASION

22. Figure 15–21 This hydromulcher is spraying a mixture of seed, fertilizer, and chemical
mulch on the road cut. The chemical mulch holds the seed in place and protects the
slope from erosion until the grass germinates and becomes established. (Photo: B. Kay.)

23. Damages of Wind Erosion
• Losing topsoil has a direct effect on the productivity of
the land. A loss of 2.5 cm of soil can reduce wheat yields
by 5-10% while a loss of 20 cm can reduce yields to 1/3
of their previous levels. Estimated soil loss by wind
erosion on the is 160 million tones per year.
• As soil productivity decreases due to a decrease in
topsoil, soil fertility becomes less.
• Organic material is reduced and hence, less plant growth
occurs.

24. •The effect of wind erosion on the soil is the impact of drifting
soil itself.
•Young seedlings are uprooted.
•Soil covers plants and seeds.
•Roads,railways and fences are covered by soil.
•It creates air pollution

25. How to control wind erosion?
• Proper soil and range land management is the key
to reducing the effects of wind on the land.
• Following are the main steps to control wind
erosion.
• Planting shelterbelts (trees may be obtained from
the Tree Nursery) to help reduce the velocity of the
wind
• Increasing the organic content of the soil
• Using fertilizers to increase soil productivity

26. • Alternating narrow strips of summer fallow and
crop perpendicular to the prevailing winds
(strip cropping)
• Leaving stubble barriers
• Using trash cover and green manure
• Reducing tillage
• Using marginal land for livestock rather than
crop production

27. • Reducing the speed of tillage
• Planting of fall cover crops (winter wheat or rye) in
areas of light, sandy soil which are particularly prone
to wind erosion
• Using marginal land for livestock rather than crop
production
• Reducing the speed of tillage
• Planting perennial grass or legumes on grazing
lands
• Zero tillage - planting crops in to last years' stubble

28. •The more organic material present in the soil, the
greater the resistance of the soil to be broken into
particles small enough to be carried away by wind or
water, and the more moisture the soil will hold.
Adding fertilizers to the soil aids in making the soil
more productive, which protects it against the
effects of erosion.

29. • USE OF CROP RESIDUES TO COVER
SOIL

30. • Shelterbelts are designed to slow down the
speed of the wind. Along with upright stubble,
shelterbelts can help to accumulate snow cover
in the winter.
• Mulching
• Strip Cropping

31. • STRIP CROPPING

32. Some Additional Points For Controlling
Wind Erosion
• sufficient area upwind should be tilled -- not just
the area presently blowing.
• The direction of emergency tillage should always
be at a right angle to the wind for maximum
protection.
• For row crops, it may be necessary to compromise
by following the row pattern instead of the
prevailing winds. If old crop stubble remains, the
emergency tillage tool should run between rows,
leaving as much upright stubble in the rows as
possible.
• Tractor speed and tillage depth should be varied
as needed to bring clods to the surface. The best,
most effective clods come from moist soil. Slower
travel speeds with tillage implements will build
higher ridges and more protection.