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Soils of Africa

Soils of Africa. Meredith Albright Rande Kamolz Wade Grewe. Introduction Climate, Biomes, and African Soils Great Crisis in Africa: Desertification Fire and soil degradation. Introduction Soil Moisture. Characterized by soil moisture stress Over 86% of Africa is moisture stressed

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Soils of Africa

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  1. Soils of Africa Meredith Albright Rande Kamolz Wade Grewe

  2. Introduction • Climate, Biomes, and African Soils • Great Crisis in Africa: Desertification • Fire and soil degradation

  3. IntroductionSoil Moisture Characterized by soil moisture stress Over 86% of Africa is moisture stressed Precipitation Soil type

  4. Aridisols - 26.4% • Sahara and Kalahari deserts • Entisols – 24.5% • Lightly weathered – dry areas • Oxisols – 14.3% • Sombic horizon (OM accumulation) in Rwanda and Burundi • Alfisols – 10.5% • Argillic horizon • Relatively higher fertility • Ultisols – 6.2% • Argillic horizon, deep, well-drained soil • Low fertility Introduction Primary Soil Types

  5. Climate and Soil Relationship Soils Climates

  6. Currents Climates

  7. Desertification of Soil • Degradation of land and soil in arid, semi-arid, and dry sub-humid environments • Causes • Poor land management • Climatic variation • Salinization • Became mainstream during the Sahelian Drought that began in 1968 • Led to the deaths of more than 100,000 people and millions of livestock by 1973

  8. Human-InducedDesertification Areas of Vulnerability

  9. Fire-induced soil changes • Natural occurrence in savanna and grasslands • Create/maintain agricultural areas • Soil degradation concerns • Focus: South African soil • Fine, sandy loam Dr. Michael D. King, NASA Earth observatory www.kirkanddonna.com/rtw/pics/0713Savannah.jpg

  10. Crust Formation • Compaction • Mechanical impact of raindrops break down aggregates • Clay dispersion • Fire-induced low-salt environments

  11. Flocculation Clay dispersion • High saltconcentration • Flocculation creates macro-pores • High water infiltration • Low saltconcentration in soil solution • Clay dispersion clogs pores • Low infiltration macro-pore no macro-pores • _ +-+ +- - +-+ + +- + + + + - - - - +- + + +- + + - + +- - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + + • _ • _ • _ clay + + + + + + + + + + + + + • _ • _ • _ • _

  12. Soil Consequences • Decreased water infiltration • Decreased organic matter • Decreased aggregation • Decreased water storage capacity http://www.geography.learnontheinternet.co.uk/images/ecosystems/savanna.jpghttp://www.ciat.cgiar.org/africa/images/f_afnet3.jpg http://www.nigeldennis.com/stock/images/landscapes/sa/kalahari/65000.jpg

  13. Environmental and Social Consequences • Decrease soil quality – natural vegetation • Reduced long-term agricultural stability • Reduced food security • Solution – termites may control crust formation www.kirkanddonna.com/rtw/pics/0713Savannah.jpg images.jupiterimages.com/common/detail/72/51/22565172.jpg

  14. Summary • Where and Why • Broad spectrum of soil types • Biomes • Weathering • Desertification is a rapidly growing concern due to intensive land use and increasing demand for crop production. • Unnaturally frequent fires degrade soil • Decrease agricultural stability • Reduce food security

  15. References • Brady, N.C., R. Weil, 2008. The Nature and Properties of Soils, Fourteenth edition. Pearson Prentice Hall, Columbus, Ohio, pp 420-423. • King, Michael, 2007. Nasa Earth Observatory - http://earthobservatory.nasa.gov/ • Mando, A., L. Stroosnijder, L. Brussaard, 1996. Effects of termites on infiltration into crusted soil. Geoderma 74: 107-113 • Mills, A.J., M.V. Fey, 2004a. Frequent fires intensify soil crusting: physiochemical feedback in the pedoderm of long-term burn experiments in South Africa. Geoderma 121: 45-64. • Mills, A., M. Fey, 2004b. Transformation of thicket to savanna reduces soil quality in the Eastern Cape, South Africa. Plant and Soil 265: 153-163. • Snyman, H.A., 2003. Short-term response of rangeland following an unplanned fire in terms of soil characteristics ina semi-arid climate of South Africa. Journal of Arid Environments 55: 160-180. • Valentin, C., J.L. Rajot, D. Mitja, 2004. Responses of soil crusting, runoff and erosion to fallowing in the sub-humid and semi-arid regions of West Africa. Agriculture, Ecosystems and Environment 104: 287-302. • University of Minnesota, 2004. Unit 10 – Soils of Africa. http://www.soils.umn.edu/academics/classes/soil4505/doc/unit10af.htm

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