Question 2
(a) (i) Define the term irrigation (2 marks)
(ii) Give four reasons why irrigation is necessary in West Africa. (4 marks)
(iii) State three differences between the following irrigation systems.
Use of sprinklers |
Surface irrigation |
|
|
|
|
|
|
(3 marks)
(c) Mention five ways in which agriculture and industry are interrelated. (5 marks)
(d) Name one crop disease transmitted by each of the following insect vectors:
(i) leafhopper;
(ii) mealybug;
(iii) aphid;
(iv) whitefly. (4 marks)
Observation
Many candidates were mentioning climatic factors as it affects irrigation and not
the importance of irrigation in Question 2(a)(ii). Furthermore, most candidates could
not differentiate between sprinkler and surface irrigation as well as mention the crop
diseases transmitted by the insect vectors in Question 2(b) and (c) respectively.
The expected answers include:
2. (a) (i) Definition of irrigation
- Irrigation is the artificial application of water to the soil in order to
supplement insufficient rainfall
(ii) Reasons why irrigation is necessary in West Africa
- Helps seeds to germinate/improves crop growth when rain is erratic
- Facilitates crop husbandry during the dry season/throughout the year
- Makes early planting possible
- Prevents wilting of crops
- Improves ground water storage
- Improves the productivity of land during drought
- Increases the yield of crops
- Reduces the concentration of salts in the soil
- Helps in dissolution of fertilizer/nutrients in the soil
- Encourages soil microbial activities
- Softens the soil for easy tillage operation
- Reduces soil temperature/cools the soil
- Provides moisture for root absorption
(iii) Differences between the use of sprinklers and surface irrigation
Use of sprinklers |
Surface irrigation |
- Expensive to install |
- Cheap to construct |
- Expensive to maintain |
- Cheap to maintain |
- Requires technical skill |
- Easy to operate |
- Water is applied in form of |
- Water flows on soil surface by |
- Suitable for all kinds of |
- Requires a gentle slope/levelled |
- Could be used to apply inorganic |
- Cannot be used to apply inorganic |
- Water is applied above the soil |
- Water is applied on the soil |
- Requires a network of pipes to |
- Requires ditches/channels to |
- Saves water/water is efficiently |
- Wastes water |
- Spray of water is affected by wind |
- Flow of water is not affected by |
(b) Ways in which agriculture and industry are interrelated
- Agriculture provides raw materials for industries
- Agriculture provides food for industrial workers
- Agriculture provides market for industrial products e.g. farm machinery, agrochemicals
- Industry produces machinery and equipment for agricultural uses e.g. tractor, plough
- Industry produces agrochemicals for agricultural uses e.g. pesticides, fertilizers, herbicides
- Both agriculture and industry compete for labour/factors of production
- Industry provides household utensils for farmers
- Industry provides improved facilities/structures for storage and processing of
agricultural products e.g. silo
(c) Crop diseases transmitted by insect vectors
(i) Leaf hopper
- Maize streak - Tobacco streak
(ii) Mealy bug
- Cocoa swollen shoot disease - Cocoa mottled leaf
- Banana streak
(iii) Aphid
- Groundnut rosette - Cowpea mosaic
- Citrus die-back
(iv) Whitefly
- Cassava mosaic
- Cotton leaf curl