Question 3
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- Define the term drainage. (2 marks)
- State four reasons why waterlogged agricultural land should be drained (4 marks)
- List six factors affecting nutrient availability in the soil.(6 marks)
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Complete the table below on the causative organisms of crop diseases
(6 marks)Disease Causative organism Rice blast (i) Groundnut rosette (ii) Cassava mosaic (iii) Root knot of tomato (iv) Maize rust (v) Tristeza (vi)
Observation
Majority of candidates who attempted this question found question 3(c) challenging. They were unable to name the causative organism of the various crop diseases listed.
The expected answers include:
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Definition of drainage
Drainage is the removal of excess water/soil moisture from the soil.
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Reasons why waterlogged agricultural land should be drained
- Improves soil temperature
- Improves aeration of the soil
- Supports the decomposition of organic matter in the soil to enhance the nutrients’ status/enhances mineralization of organic matter
- Excess salts that would be toxic to plants are removed with drained water
- Improves soil structure
- Makes land available for cultivation/makes tillage operations easy
- Enhances seed germination/proper development of plant
- Regulates soil pH
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Definition of drainage
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Factors affecting nutrient availability in the soil
- Vegetative cover - Bush burning
- Soil type/nature of soil - Soil texture
- Soil structure - Soil pH
- Topography - Leaching
- Erosion - Crop removal/weeding
- Soil water content - Cultural practices adopted
- Activities of soil microorganisms - Oxidation and reduction
- Nutrient imbalance/excess of other nutrients -
Causative Organisms of crop diseases
Disease Causative organism Rice blast Fungus (Piricularia oryzae) Groundnut rosette Virus Cassava mosaic Virus Root knot of tomato Nematode (Meloidogyne spp) Maize rust Fungus (Piricularia oryzae) Tristeza Virus