WAEC SSCE - Agricultural Science - 2008 (Practical)

Maelezo ya Majibu

(a) Class of manure

• Specimen A (poultry droppings): organic manure (animal manure).
• Specimen B (N-P-K 15-15-15): inorganic or chemical fertilizer (a compound fertilizer).

(b) Three characteristics of each specimen

Specimen A (poultry droppings)

1. It is bulky and low in nutrient concentration.
2. It contains organic matter and adds humus to the soil.
3. It releases its nutrients slowly and has an offensive smell.

Specimen B (N-P-K 15-15-15)

1. It is concentrated and high in plant nutrients (15% N, 15% P, 15% K).
2. It is not bulky and dissolves readily, so nutrients are quickly available.
3. It is manufactured and does not add humus to the soil.

(c) Two precautions when applying each specimen

Specimen A

1. It should be well decomposed (cured) before application to avoid scorching and weed seeds.
2. It should be worked into the soil and hands washed after handling.

Specimen B

1. Apply only the recommended rate and keep it away from the plant base to avoid scorching the crop.
2. Store in a dry place and wear protective gloves to avoid contact with the skin.

(d) Specimen recommended to improve clay soil

Specimen A (poultry droppings) is recommended. Reasons:

1. It adds organic matter and humus that improve the structure, aeration and drainage of the heavy clay soil.
2. It encourages the activity of soil organisms and binds particles into crumbs, whereas Specimen B only supplies nutrients and does not improve the soil's physical condition.

Maelezo ya Majibu

(a) Identification of specimens

• Specimen I: Liver
• Specimen J: Ruminant skin (hide)
• Specimen K: Rumen

(b) Functions of the specimens to the animal

Specimen I: Liver

• It produces bile, which helps in the digestion of fats.
• It stores excess glucose as glycogen and releases glucose when needed.
• It detoxifies harmful substances, such as poisons and drugs, in the blood.

Specimen J: Ruminant skin

• It protects the body against injury, disease-causing organisms and dehydration.
• It helps to regulate body temperature through sweating and changes in blood flow near the skin surface.
• It contains sensory receptors that enable the animal to feel touch, pain, pressure and temperature.

Specimen K: Rumen

• It temporarily stores swallowed feed.
• It contains microorganisms that digest cellulose in fibrous plant materials.
• It allows fermentation of food and absorption of some products of fermentation, especially volatile fatty acids.

(c) Process used in preserving fresh milk

The process is pasteurisation. Milk is heated to a controlled temperature for a short time and then cooled rapidly. This destroys most harmful microorganisms and helps the milk remain fresh for longer. The wording of this part appears unclear, but pasteurisation is the standard process for preserving fresh milk.

(d) Products that can be produced from milk

1. Butter
2. Cheese
3. Yoghurt
4. Cream
5. Ice cream

Examination reminder: Give functions specifically related to the animal. For example, the rumen is important for microbial digestion of cellulose, whereas the liver is important for bile production, storage of glycogen and detoxification.

Maelezo ya Majibu

(a) Identification of the equipment

• C: Incubator
• D: Milking machine

(b) Parts labelled I to VII

• I: Thermometer
• II: Egg
• III: Egg tray
• IV: Water
• V: Source of heat
• VI: Teat cup
• VII: Source of power / vacuum pump

(c) Precautions when using each equipment

C: Incubator

1. Set only clean, fresh, fertile eggs that have not been stored for more than two weeks.
2. Do not wash the eggs with water, as this increases the porosity of the shell and raises the respiration of the embryo.
3. Arrange the eggs with the air-space (broad) end up and set uniformly sized eggs, keeping the incubator away from walls for proper ventilation while constantly monitoring the temperature and relative humidity.

D: Milking machine

1. Clean and scrub the udder and teats thoroughly with slightly warm water before milking, and test the foremilk with a test cup.
2. Handle the dairy animal gently and apply only light pressure, avoiding noise or distraction such as smoking or drinking during milking.
3. Introduce some feed and provide light, soft music to induce the animal to let down its milk, while the milker concentrates fully on the task.

Maelezo ya Majibu

(a) Identification of specimens

• Specimen E: Maize weevil.
• Specimen F: Cotton stainer bug (Dysdercus).
• Specimen G: Termite.
• Specimen H: Grasshopper.

(b) Part of the plant usually attacked by each

• E (maize weevil): maize grains (stored cereal grains).
• F (cotton stainer bug): cotton bolls, okro fruits and akee apple.
• G (termite): crop stems, roots and grains of lodged cereals.
• H (grasshopper): plant leaves and young shoots.

(c) Two ways by which each specimen damages crops

Specimen E (maize weevil):

1. Bores into the grains of maize, creating holes and destroying the embryo so that the grain cannot germinate.
2. Eats the endosperm, reducing the food value; the vents created serve as sites for secondary infection.

Specimen F (cotton stainer bug):

1. Pierces into mature cotton bolls, okro fruits and akee apple, staining the cotton lint and preventing good fruit formation.
2. Causes premature drop of fruits; the vents created serve as sites for secondary infection.

Specimen G (termite):

1. Chews the stems and roots of plants and tubers, weakening them so that the plants lodge.
2. Destroys seed grains lying on the field and creates tunnels that serve as sites for secondary infection.

Specimen H (grasshopper):

1. Causes defoliation of crops and destroys young shoots and buds, reducing the photosynthetic ability and growth of the crop.
2. The wounds left on the crops serve as vents for secondary infection.

(d) Three methods of controlling specimen E (maize weevil)

1. Dry the grains very well before storing and store them in air-tight (hermetic) containers.
2. Apply approved pesticides to the grains before storage and fumigate the storage facilities.
3. Store the grains with hot dried pepper or neem extracts, or use smoke to kill and ward off the weevils; harvest early soon after drying.