This question tests four separate areas of agricultural science: the economics of produce marketing, extension teaching methods, plant pathology, and crop improvement. Each part is answered under its own heading so the distinct marking points stay clear.
(a) Four reasons why the prices of most agricultural produce are unstable in West Africa
Price instability means the price of a commodity rises and falls sharply over time rather than staying steady. For farm produce this happens because both supply and demand behave in unusual ways:
- Seasonal production. Most crops are harvested within a short season, so supply is very large just after harvest (a glut, which pushes prices down) and very small in the off-season (scarcity, which pushes prices up). The same crop therefore fetches very different prices at different times of the year.
- Perishability of produce. Fruits, vegetables, tubers and other fresh produce spoil quickly and cannot be held back for long. Farmers are forced to sell whatever they harvest almost immediately, so a temporary surplus cannot be smoothed out and prices collapse during a glut.
- Dependence on weather, pests and diseases. Output is controlled largely by rainfall, drought, flood, and pest or disease outbreaks, which the farmer cannot control. A good season floods the market and lowers prices, while a poor season creates shortage and raises prices, so supply and price swing from year to year.
- Inelastic demand together with poor storage, processing and transport. The demand for staple foods changes little even when supply changes greatly, so a small change in the quantity available causes a large change in price. Weak storage, processing and transport facilities also cause heavy wastage and prevent produce from being moved from surplus areas to scarce areas, worsening the swings.
(b) Two agricultural extension methods explained
Agricultural extension is the education of farmers to help them adopt improved practices. The two named methods differ mainly in scale and in how directly the farmer takes part.
(i) Method demonstration. This is a teaching method in which the extension agent physically shows a small group of farmers, step by step, exactly how to carry out a particular skill or operation, for example how to bud or graft a seedling, mix and apply a spray, dress seed, or vaccinate a bird, and then allows the farmers to practise the skill themselves under guidance. It teaches a specific "how-to-do-it" skill and is convincing because the farmers see and repeat the correct procedure with their own hands.
(ii) Agricultural shows. These are organised exhibitions or fairs at which farmers, research institutes, input companies and government agencies display improved crop varieties, livestock breeds, farm inputs, tools and machinery, often with competitions and prizes for the best entries. They educate a very large audience at once and motivate farmers to adopt better varieties, breeds and equipment by letting them compare results and see what improved practice can achieve.
(c) Cercospora leaf spot disease
| Heading | Answer |
|---|
| Crop affected | Groundnut (it also attacks other legumes such as cowpea). |
| Causative agent | A fungus, Cercospora species (for example Cercospora arachidicola on groundnut). |
| Mode of transmission | Air-borne spores spread by wind and by rain splash, and carried over between crops on infected plant debris and seed. |
| Two symptoms | (1) Brown to dark brown, roughly circular spots appear on the leaves, often surrounded by a yellow halo. (2) The spots enlarge and merge, the leaves turn yellow and fall off, causing premature defoliation and reduced yield. |
| One preventive measure | Spray the crop with a suitable fungicide (other acceptable measures include planting resistant varieties, practising crop rotation, using clean healthy seed, and destroying infected crop residues). |
(d) Four advantages of selection as a method of crop improvement
Selection means choosing plants with the most desirable characters from a population and using them as the parents or seed source for the next generation.
- It is cheap, simple and does not require specialised laboratory equipment, so ordinary farmers can practise it.
- It preserves and multiplies the best or most desirable characters already present in the crop, such as large seed size or good taste.
- It steadily improves yield and quality over successive generations as only the best plants are bred forward.
- It helps develop varieties that are better adapted to local conditions and more resistant to pests, diseases, drought and other adverse factors.
Examination reminder: In part (a) make each point a genuinely different cause (do not list "perishable" and "spoils quickly" as two separate reasons), and in part (c) keep your answers strictly under the given headings, giving the causative organism as a named fungus rather than a vague "germ".
