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SOIL


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OVERVIEW

The pedosphere is a highly organized physical, chemical and biological system with characteristic properties. Soils vary from place to place but several main groups are recognized in soil classification schemes. Owing to its role in sustaining life, soil should be one of humanity’s
most prized assets. In using soil, however, humans cause local and regional soil
degradation. Soil degradation takes several forms. Erosion by water and wind are common.
Biological degradation involves changes in humus content and the loss of animal and plant life.
Physical degradation is the loss of structure and change in permeability, with the related changes
in soil drainage. Chemical degradation includes acidification and a loss of soil fertility, alkalization,
and changes in acidity, salinity and chemical toxicity. The non-sustainable use of soils leads to
the Dust Bowl Syndrome and a number of other syndromes, including land contamination through
industrial pollution, that are far-reaching in time and space. Soil erosion, by both wind and water,
may be reduced by the application of suitable conservation strategies. Globally, soils are a
crucial link in the carbon cycle. Their more climatically sensitive properties, such as nitrogen
and carbon levels, can be expected to respond to a rise in global temperatures. Many soils would
probably emit more carbon dioxide, so accelerating the warming effect.

LEARNING OUTCOMES

This chapter will help you to understand:

• How to describe soil properties
• Systems of soil classification
• Degradation of soil associated with mismanagement
• Environmental issues concerning soils, including soil erosion, soil salinity and soil
  contamination.
  

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SUMMARY

Soils are an essential part of global environmental systems and processes. Together with water, soils are immensely important to human societies in the production of crops for humans and grazing plants for animals.

This chapter has looked at the basic processes underpinning soil formation and soil properties, and at the impacts of human activities on soil conditions. The mismanagement of soils, from contamination to erosion caused by overgrazing, causes problems that will remain for many generations to come.

Soils have an important part to play in climate change, due to their importance in carbon and nitrogen cycles, and the effects of climate change, particularly temperature and precipitation, will impact on land suitability for agriculture, and in those areas already on the edges of overproduction, upon world food supply.

QUESTIONS

1. What are the dominant soil-forming    processes? How do these differ in different    climatic zones? 4. How can the risk of soil contaminations    and pollution be minimized? 2. What are the principal causes of soil    erosion and how can they be managed? 5. What can be done to increase food    security and yet simultaneously protect    vulnerable soil reserves? 3. What are the short- and long-term effects    of overgrazing and erosion, not only for the    soil but also for the local economy as a    whole? 6. What might be the impact of climate    change on soils and the ability of soils    to support agricultural systems?

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FURTHER READING

• Brady, N. C. (1990) The Nature and Properties of Soils, 10th edn. London: Collier Macmillan.
  An excellent introductory text aimed at soil scientists and covering a range of topics. Well worth looking at.
  
• Bridges, E. M. (1997) World Soils, 3rd edn. Cambridge: Cambridge University Press.
  A very good introduction to all types of soils and soil-forming processes.
  
• Ellis, S. and Mellor, A. (1995) Soils and Environment. London: Routledge.
  A refreshingly different approach to soils and contemporary environmental issues.
  
• Rowell, D. L. (1994) Soil Science: Methods and Applications. Harlow: Longman.
  An excellent book covering laboratory experiments and methods used in determining soil properties.