Observation

This question was fairly popular among candidates. Candidates were able to state the importance of forests to man and the effects of organic manuring, bush burning, tillage and clean clearing on the soil.
 
The expected answers include:
3.(a)Ways in which forest is important
             -     Some of the plants are used as food
             -     Some of the plants provide medicines
             -     Trees provide fuel/wood for cooking
             -     Shade of trees prevent soil erosion
             -     Forests provide employment
             -     It provides abode for wildlife
             -     It serves as tourist attraction centres
             -     It provides raw materials
             -     Leaves decay and increase soil fertility
             -     Trees are used for research and educational purposes
             -     It purifies the environment
             -     Source of revenue
             -     Source of income to individuals
             -     Serves as wind breaks
             -     Checks desertification
             -     Induces rainfall/modifies the micro-climate
             -     Protects water bodies/water shed

(b)  Effects of the following practices on the soil
(i) Organic Manuring

•  Increase in soil fertility
• Improvement of activities of soil microbes
• Increase in soil water holding capacity in sand
• Increase in soil cation exchange capacity
• Organic matter acts as soil buffer
• Improvement of soil structure
• Controls soil erosion
• Improves soil aeration
• Improves water infiltration in clay soil
• Regulates soil temperature
• Used for the control of nematodes in the soil

(ii) Bush Burning

• Sterilization of the soil
• It increases soil temperature
• Causes loss of nitrogen and sulphur
• Destroys soil organic matter
• Exposes soil to erosion/leaching
• Nutrient elements such as potassium and phosphorus are released into the soil
• Destroys weed seeds in the soil
• Population of useful soil organisms is reduced
• It stimulates the growth of fresh grasses, especially during dry season
• It increases the soil PH
• It destroys the soil structure

(iii) Tillage

• Creates favourable tilth for seed germination/improves soil structure
• Infiltration of water is enhanced
• Soil aeration is increased
• Weeds are destroyed by tillage
• Disease pathogen may spread
• Soil erosion may increase
• Leads to soil compaction
• It exposes soil organisms to harsh environmental conditions

(iv)  Clean Clearing

• Exposes soil to agents of erosion
• Reduces soil micro- organisms
• Leads to destruction of soil structure
• Exposes soil to direct sunlight which results in evaporation of soil water
• May result in increased soil temperature
• Leads to reduction of organic matter/ soil nutrients
• It causes imbalance in the ecosystem