WAEC SSCE - Agricultural Science - 2006 (Practical)

(a) Primary source of specimens J and L

Both specimen J (saw dust) and specimen L (charcoal) are obtained from wood/timber, that is, forest trees. Saw dust is the waste produced when timber is sawn, while charcoal is produced by the controlled burning of wood.

(b) Uses of the specimens

Four uses of specimen J (saw dust):

• For making particle boards and ceiling boards.
• As a source of fuel and for smoking fish.
• As litter/bedding material in poultry and animal houses.
• As mulch and organic matter, and as a planting medium in seed boxes.

Four uses of specimen K (piece of plank):

• For constructing farm buildings and structures such as pens, cribs and hutches.
• For making farm furniture.
• For making handles of farm tools such as knives, cutlasses and dibbers.
• For packaging agricultural produce and for making crates and boxes (also as fuel and for paper production).

Two uses of specimen M (honey):

• As food and a natural sweetener.
• For medicinal purposes and in the production of cosmetics and pharmaceuticals.

(c) Three ways of ensuring continuous supply of the primary source of specimen K (timber/forest trees)

• Planting seedlings of suitable, fast-growing forest tree species (afforestation and reforestation).
• Practising selective and controlled felling instead of clear felling, and encouraging regeneration of stumps.
• Enforcing forestry regulations, protecting forest reserves and preventing bush burning.

Specimen A is a soil sample, and the chemical property tested is its reaction (pH), using distilled water (D), a beaker (E), a stirring rod (F) and red and blue litmus papers (C1 and C2).

(a) Report on the test of a chemical property of specimen A

• (i) Aim: To determine the reaction (pH) of the soil in specimen A, that is, whether it is acidic, neutral or alkaline.
• (ii) Procedure: Wash a beaker (E) and rinse it with distilled water. Put a small quantity of the soil (A) into the beaker and add distilled water (D). Stir the mixture thoroughly with the stirring rod (F) and allow it to stand for a few minutes to settle. Dip the red litmus paper (C1) and the blue litmus paper (C2), one at a time, into the soil solution and observe the change in colour.
• (iii) Observation: The red litmus paper (C1) turned blue, while the blue litmus paper (C2) remained unchanged.
• (iv) Conclusion: The soil in specimen A is alkaline (basic) in nature.

(b) Two probable causes of the observed soil condition (alkalinity)

• Continuous application of alkaline fertilisers such as potash, or over-liming of the soil.
• The chemical composition of the parent rock, and arid conditions in which basic salts accumulate rather than being leached away.

(c) Four reasons why the experiment is important in agriculture

• It enables the farmer to determine the pH of the soil.
• It guides the choice of crops to grow, since crops differ in the soil reaction they tolerate.
• It shows whether plant nutrients will be available to crops, since availability depends on soil pH.
• It helps in deciding the type of fertiliser or amendment (such as lime or sulphur) to apply.

(a) Identification of the implements

• Specimen H: Disc plough.
• Specimen I: Mouldboard plough.

(b) Names of the parts labelled I - X

1. Point of attachment to the tractor (coupling point / hitch)
2. Beam (frame)
3. Scraper
4. Disc
5. Furrow wheel (rear wheel)
6. Leg (standard)
7. Coulter
8. Share
9. Mouldboard
10. Standard (leg)

(c) One function of each of parts I - IX

(a) Identification of the specimens

• Specimen N: Water lettuce (a floating aquatic weed).
• Specimen O: Catfish (Clarias spp.).
• Specimen P: Tilapia (Tilapia spp.).

(b) Relationship between specimens O and P

It is a predator-prey relationship. The catfish (O) feeds on the fries and fingerlings of the tilapia (P), thereby helping to control the population of the tilapia in the pond.

(c) Five economic importance of specimen N (water lettuce) in an aquatic ecosystem

1. It serves as food for some herbivorous fish.
2. It provides a breeding ground and shelter that hides fish from predators.
3. It limits the penetration of light into the pond and hinders proper aeration.
4. It takes up nutrients that would otherwise be used by the planktons and competes with fish for dissolved oxygen through root respiration.
5. It hinders the free movement of aquatic organisms, interferes with fish harvesting and increases the cost of fish production.

(d) Three benefits of stocking specimens O and P together in the same pond

1. Population control: the catfish (O) preys on excess tilapia (P) fingerlings, preventing overcrowding and stunted growth so the survivors reach marketable size.
2. Fuller use of the pond and feed: tilapia feed mainly in the upper and middle water while catfish feed at the bottom, so all feeding levels and available food are used, giving a higher total yield.
3. Higher and more varied income: two marketable species are harvested from one pond, spreading risk and increasing the farmer's profit.