1. Soil Degradation and Loss of Nutrients in Soils in Africa -Lesego N. Olefhile 05.01.2002

3. General Continent has been occupied by humans much longer than other continents Human activity and it’s repercussions Bedrock mainly granite and gneiss Low fertility Rocks oldest in the world Low clay-easy to work & easy to lose

5. Intro’ & Overview What is SD Types Causes Impact/Effects of SD Control & Prevention (Solutions) Comments

6. What is Soil Degradation Soil Degradation is a Reduction in the Soils Ability to Produce Qualitatively & quantitatively Results in decreased food production Declining yields Increasing levels of poverty

7. What is SD (Cont’) Slight Degradation 10% Yield Potential Reduction Moderate Degradation 10-50 % YPR Severe Degradation >50 % YPR

9. Types or Mechanisms of SD Water Erosion Wind Erosion Chemical degradation Physical degradation

10. Chem. and Phy. Degradation Chemical Degradation Leaching – loss of soil nutrients Salinization – dry lands –minerals accumulation on the surface - caliches Physical Degradation Waterlogged

11. Mechanisms of SD (conti’)

12. Wind & Water Erosion Erosion is the major cause of soil degradation Water erosion more severe (vol. & land area) Major concern in Southern Africa

13. Causes of SE Monoculture Common practice in Africa Deforestation-Fuel -Building materials 37 million ha of forest disappearing each yr (FAO, 1986) Marginal lands farming- pop. Increase Hillsides Malawi 12% slope land cultivated (FAO)

14. Causes of SE (cont’) Row cropping Crop removal Overgrazing Accounts for about half of the soil degradation in Africa-(FAO) Tilling or plowing All lead to Soil Degradation

15. SE in Africa Most erosion occurs in Liberia, Guinea,Ghana, Nigeria, Zaire,Ethiopia, Senegal, Niger, The Sudan,Somalia and Sierra Leone -FAO Ethiopia – 1,900 T of soil lost annually from the highlands -UN

16. Causes of Soil Degradation Deforestation Exceeds planting by 30:1 in most parts of Africa Overexploitation Overgrazing Agric activities (other) Industrialization

18. SD vs desertification Desertification= degradation of land in dry areas of the world due to misuse or overuse Advanced Soil Degradation Destroys soil’s capacity to support livestock or grow crops 24 million tones of top soil every yr over the world Costs Africa about US$9 billion per year (UN) Not the spread of existing deserts!!

19. Loss of nutrients Loss of top soil Loss of soil minerals Many areas in Africa losing about 50 tones of soil/ha/yr Equivalent to loss of 20,2 & 41 billion tones of N,P & K respectively per yr. -UNEP

20. Impact of Soil Degradation Decline in soil fertility Decline in biomass produced Decrease in food production Starvation & Poverty By 2025 Africa ‘ll feed only 40% of it’s pop (FAO) > ¼ of Africa becoming useless for cultivation due to SD. -UNEP

21. Solutions Implementation of Govt. Policies -Soil erosion prevention schemes Precision Ag??? Advanced farming methods - conservation tillage GLASOD - Global Assessment of Soil Degradation –estimates extent & severity of SD.-sponsored by UNEP & ISRIC

22. Setbacks (developing countries) $$$ Skilled manpower(lack of) Tradition & culture

23. Comments &/or Questions Is there a direct link between erosion and soil degradation??? Can degraded soils be restored to full function? Lightly and mod. Degraded soils NOT severely Degraded soils!!