WAEC SSCE - Agricultural Science - 2016 (Practical)

The diagram shows three identical setups labelled I, II and III. In each, a funnel holds a soil sample, with a plug of cotton wool at the neck of the funnel. Each funnel is mounted over a measuring cylinder which collects the water that passes through the soil. The three funnels hold soils of different texture, and the amount of water collected in each cylinder differs.

(a) Suitable title (1 mark)

An experiment to determine the rate of water percolation (drainage/permeability) through different soil types.

(b) Procedure (7 marks)

1. Set up three funnels of equal size and place a plug of cotton wool of equal thickness in the neck of each, to hold back the soil while letting water pass.
2. Weigh out equal masses of three different soil samples (sample I, II and III) and place one sample in each funnel.
3. Mount each funnel on a clean, dry measuring cylinder so that water dripping through is collected.
4. Measure out an equal volume of water (for example \(100\ \text{cm}^3\)) for each setup using a measuring cylinder.
5. Pour the water gently onto the surface of each soil sample at the same time and start a stopwatch.
6. Allow the water to percolate for the same fixed time (for example 5 minutes), then read the volume of water collected in each cylinder.
7. Record the volumes for I, II and III and compare them. The soil that allows the largest volume through in the given time has the highest permeability; the soil that allows the least has the poorest drainage.

(c) Identity of the soil samples

• Diagram I - Clayey soil (fine, closely packed particles).
• Diagram II - Loamy soil (mixture of medium sized particles).
• Diagram III - Sandy soil (coarse, loosely packed particles).

(d) Two precautions (2 marks)

1. Use equal masses of soil, equal volumes of water and cotton wool plugs of equal thickness in all three setups, so the comparison is fair.
2. Pour the water onto all three samples gently and at the same time, and read the collected volume at exactly the same time interval to avoid errors.

(e)(i) The soil most prone to waterlogging is sample I (clayey soil).

(e)(ii) Clayey soil has very fine particles and small pore spaces (low porosity and low permeability), so water drains through it very slowly and collects on and within the soil, leading to waterlogging. This is confirmed in the experiment by the small volume of water passing into cylinder I compared with the larger volumes collected under the loamy (II) and sandy (III) samples.

(a) Description of specimen A (ranging pole)

A ranging pole is a straight, round metal or wooden pole about 2 to 3 metres long, pointed with a metal shoe at the lower end so that it can be driven into the ground, and painted in alternating bands of red and white (or black and white) at intervals of 0.5 metre so that it can be seen clearly from a distance.

(b) Two uses of each specimen

(c) Two ways of maintaining each specimen

(a)(i) Classification of G and H by feeding habit

• Specimen G (grasshopper): a biting and chewing insect pest.
• Specimen H (bean beetle): a biting and chewing insect pest (its larva and adult chew/bore into the seed).

(a)(ii) Part of crop damaged by each

• Grasshopper (G): damages the leaves of the crop.
• Bean beetle (H): damages the seeds/grains (cotyledons of stored beans).

(a)(iii) Three ways specimen H (bean beetle) is economically important

1. It bores into and eats stored bean seeds, reducing the weight and quantity available.
2. It lowers the market value and quality of the beans, causing financial loss.
3. It destroys the germinating power (viability) of seeds meant for planting, and its holes allow entry of moulds that spoil the produce.

(b) Four ways of controlling specimens I and J

(a) Three industries that use specimens N (bone) and O (egg)

(b) Five effects of specimen P (roundworm) on the host

1. It feeds on digested food in the gut, causing loss of nutrients, emaciation and loss of weight.
2. It causes anaemia and general weakness of the animal.
3. Heavy infestation blocks the intestine and may cause pot belly and digestive disturbance.
4. It lowers productivity, that is reduced growth, milk, meat or egg output.
5. It damages the intestinal wall and internal organs and may cause death in severe cases.

(c) Four ways of controlling specimen Q (tick) on the farm

1. Dip or spray animals regularly with acaricides (tick chemicals).
2. Hand-pick and destroy ticks from infested animals.
3. Practise rotational grazing and clear/burn overgrown pastures to destroy the tick habitat.
4. Quarantine and treat newly bought or infested animals before mixing them with the herd, and drain marshy areas.