Soil Degradation
Corinne Waelti, seecon international gmbh
Soil Degradation
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Soil Degradation
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Contents
1. Introduction
2. Four Types of Soil Degradation
3. Human Causes of Erosion
4. Controlling Erosion
5. Conclusion
6. References
Soil Degradation
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1. Introduction
The overall Problem
What is soil degradation?
Process by which one or more of the potential ecological functions of
the soil are harmed or destroyed.
Soil degradation is an increasing global process affecting mainly arid
and semi-arid zones in sub-Saharan Africa. Principal forms are the
depletion of nutrients and soil organic matter and erosion.
The negative impacts of soil degradation may lead to partial or
complete loss of the soil’s current and/or future productive capacity.
Soil degradation can be a result of both natural hazards and
unsuitable land use.
Soil Degradation
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1. Introduction
Four Types of Soil Degradation
Water erosion
Source: PLANT and SOIL SCIENCES
ELIBRARY (2005)
Wind erosion
Soil
degradation
Chemical deterioration
Source:
http://www.unibas.it/desertnet/dis4me/issues/issue_degradation.htm
Soil Degradation
Source: RITTER (2003)
Physical deterioration
Source:
http://www.extension.iastate.edu/CropNews/2009/0430alkaisihanna
.htm
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1. Introduction
A global Problem: Human induced Soil Degradation
ISRIC et al. (1996)
Soil Degradation
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2. The Four Types of Soil Degradation
Water Erosion (1/2)
Soil particles, which are either detached by splash erosion or by the
effect of running water.
Factors influencing water erosion
Rainfall
The impact of raindrops on the
soil surface can break down soil
aggregates and disperse the
aggregate material over the
surface.
Slope gradient
Steeper and longer slopes of a
field lead to greater amount of
soil erosion by water.
Soil type
Soils with faster infiltration
rates, higher levels of organic
matter and improved soil
structure have a greater
resistance to erosion.
Soil use
Plants may protect the soil
from raindrop impact and
splash, slow down the
movement of surface runoff
and allow infiltration of excess
surface water.
BALLAYAN (2000) and INFONET-BIOVISION (2010)
Soil Degradation
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2. The Four Types of Soil Degradation
Water Erosion (2/2)
Types of water erosion
Sheet erosion
Removal of a fairly uniform layer
of soil from an entire surface
area.
Gully erosion
Rills flowing together form larger
streams and tend to become
deeper with successive flow of
water.
Rill erosion
Small channels running over
the soil surface causing deeper
incision of the channels into
the surface.
Bank erosion
Water cutting into the banks of
streams and rivers.
BALLAYAN (2000)
Soil Degradation
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2. The Four Types of Soil Degradation
Wind Erosion
Factors influencing wind erosion
Soil erodibility
Fine and medium soil particles can
be transported over great
distances. Coarse particles can be
blown along the surface.
Climate
Soil moisture levels can be very
low at the surface during periods
of drought, thus releasing
particles for transport by wind.
Soil surface roughness
Soil surfaces that are not rough
or ridged offer little resistance
to the wind.
Vegetative cover
The lack of permanent
vegetation cover may lead to
extensive erosion by wind as
loose, dry and bare soil is most
susceptible.
SHELTON (2003)
Soil Degradation
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2. The Four Types of Soil Degradation
Chemical Deterioration
Typical causes
Effects
• Municipal or industrial
wastes
• Loss of nutrients and organic
matter leading to reduced
plant growth
• Oil spills
• Excessive use of fertiliser,
herbicides and insecticides
• Release of radioactive
materials
• Airborne pollutants
• Salinisation
• Acidification
• Soil pollution
• Fertility decline
FAO/AGL (2000)
Soil Degradation
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2. The Four Types of Soil Degradation
Physical Deterioration
Typical cause
Effects
• Compaction through heavy
machines or animals
• Soil crusting
• Increased runoff
• Decreased infiltration of
water into the soil
• Prevention and inhibition of
plant growth
• Higher susceptibility to other
forms of degradation
FAO/AGL (2000)
Soil Degradation
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3. Human Causes of Erosion
Human Actions leading to Soil Degradation
• Poor agricultural practices
• Exposing soil on slopes
• Removal of forest vegetation
• Overgrazing
• Altering the characteristics of streams, causing bank erosion
• Reducing evapotranspiration losses due to vegetation removal
• Producing impervious surfaces such as roads and footpaths causing
increased runoff into streams
• Overexploitation of groundwater
ACS DISTANCE EDUCATION (2009)
Soil Degradation
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4. Controlling Erosion
The most common Control Methods
• Cover materials (e.g. plants)
• Improved crop production techniques (e.g. organic fertiliser, type of
irrigation method)
• Ploughing to destroy rills and contour planting
• Terracing
• Careful selection of land use practices
• Conservation tillage methods
• Armouring of channels to prevent bank erosion
• Wind breaks
• Ploughing into clod sizes too big to be eroded / Ploughing into ridges
 Sustainable Agriculture / Land Management
ACS DISTANCE EDUCATION (2009)
Soil Degradation
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5. Conclusion
Sustainable Land Management is crucial
No sustainable
land management
Sustainable land
management
Changes with
sustainable land
management
Degraded soil
World population
Available land
Food demand
Food production
Soil Degradation
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6. References
ACS DISTANCE EDUCATION (Editor) (2009): Soil Degradation. Stourbridge: ACS Distance Education. URL:
http://www.acsgarden.com/articles/other-gardening/soil-degradation.aspx [Accessed: 05.06.2012].
BALLAYAN, D. (2000): Soil Degradation. ESCAP environment statistics course. Rome: FAO. URL:
www.unescap.org/stat/envstat/stwes-04.pdf [Accessed: 06.06.2012].
FAO (Editor), AGL (Editor) (2000): Management of Degraded Soils in Southern and eastern Africa (MADS-SEA-Network). Rome: FAO.
INFONET-BIOVISION (Editor) (2010): An Introduction to soil degradation. Zurich: Biovision. URL:http://www.infonetbiovision.org/default/ct/184/soilManagement [Accessed: 05.06.2012].
ISRIC (Editor), UNEP (Editor), FAO (Editor) (1996): Human Induced Soil Degradation. Rome: World Food Summit. URL:
www.fao.org/docrep/003/w2612e/w2612eMap12-e.pdf [Accessed: 06.06.2012].
PLANT (Editor), SOIL SCIENCES ELIBRARY (Editor) (2005): Picture of Gully Plug Erosion. University of Nebraska-Lincoln. URL:
http://plantandsoil.unl.edu/croptechnology2005/pages/index.jsp [Accessed: 08.10.2010].
RITTER (2003): The Physical Environment. An Introduction into Physical Geography. URL:
http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/title_page.html [Accessed: 06.06.2012].
SHELTON, I. J. (2003): Soil Erosion – Causes and Effects. Ridgetown College of Agricultural Technology. Ontario Institute of
Pedology. URL: http://omafra.gov.on.ca/english/engineer/facts/87-040.htm [Accessed: 05.06.2012].
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Soil Degradation
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