(a) (i) Define the term drainage. (ii) State four reasons why waterlogged agricultural land should be drained. (b)List six factors affecting nutrient availa...
Question 1 Report
(a) (i) Define the term drainage.
(ii) State four reasons why waterlogged agricultural land should be drained.
(b)List six factors affecting nutrient availability in the soil.
(c) Complete the table below on the causative organisms of crop diseases.
| Disease | Causative Organism |
|---|---|
| Rice blast | (i) |
| Groundnut rosette | (ii) |
| Cassava mosaic | (iii) |
| Root knot of tomatoe | (iv) |
| Maize rust | (v) |
| Tristeza | (vi) |
Answer Details
(a)(i) Drainage is the removal of excess (gravitational) water from the surface and sub-surface of the soil so that the soil remains well aerated and workable.
(a)(ii) Reasons why waterlogged agricultural land should be drained:
- To improve soil aeration so that plant roots and soil organisms can respire.
- To raise soil temperature, which encourages seed germination and root growth.
- To improve soil structure and workability, allowing tillage and machinery movement.
- To remove toxic substances and prevent root-rot diseases, encouraging deeper rooting.
(b) Six factors affecting nutrient availability in the soil:
- Soil pH (soil reaction).
- Soil texture and structure.
- Organic matter (humus) content.
- Soil moisture content.
- Soil temperature.
- Activity of soil micro-organisms.
(c) Causative organisms of the crop diseases:
| Disease | Causative organism |
|---|---|
| Rice blast | (i) Pyricularia oryzae (a fungus) |
| Groundnut rosette | (ii) Groundnut rosette virus |
| Cassava mosaic | (iii) Cassava mosaic virus (a geminivirus) |
| Root knot of tomato | (iv) Meloidogyne species (root-knot nematode) |
| Maize rust | (v) Puccinia species (a fungus) |
| Tristeza | (vi) Citrus tristeza virus |
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