WAEC SSCE - Agricultural Science - 2010 (Practical)

The experiment uses specimen A (a soil sample), specimen B (water), specimen C (sodium carbonate, a deflocculating/dispersing agent) and specimen D (a tall transparent measuring cylinder or bottle). The principle is sedimentation: when soil is shaken in water and allowed to settle, the particles settle out in layers according to their size and weight.

(a)(i) Procedure:

1. Place a known quantity of the dry soil (specimen A) into the transparent cylinder (specimen D).
2. Add water (specimen B) until the cylinder is about three-quarters full.
3. Add a small quantity of sodium carbonate (specimen C) to help disperse the particles.
4. Cover the mouth of the cylinder and shake the mixture vigorously so that all the soil is thoroughly suspended in the water.
5. Place the cylinder on a table and allow it to stand undisturbed for several hours (or overnight).
6. Observe and record the layers of particles that settle at the bottom.

(ii) Observations and results: The soil particles settle in distinct layers. The heaviest and largest particles (gravel and coarse sand) settle first at the bottom, followed by fine sand, then silt, and finally the finest clay particles form the topmost layer of the sediment. Very fine organic matter (humus) floats on the surface of the water, and the water above remains slightly cloudy. This layering shows that the soil is made up of particles of different sizes.

(b) Functions of the specimens:

• Specimen B (water): it acts as the medium in which the soil particles are suspended so that they can separate and settle out according to their sizes.
• Specimen C (sodium carbonate): it acts as a deflocculating (dispersing) agent that separates the clumped soil particles from one another, so that each particle settles freely according to its true size.

(c) Three precautions:

1. Shake the mixture thoroughly and uniformly so that all the soil is properly suspended.
2. Place the cylinder on a firm, level surface and do not disturb or shake it while the particles are settling.
3. Read the levels of the settled layers at eye level to avoid parallax error.

(a) Names of specimens N, O and P

(b) Two products that can be made from specimen M (milk)

• Cheese
• Butter (butter fat)

(Other acceptable products: yoghurt, ice cream, powdered milk, skimmed milk, milk candy/butterscotch.)

(c) Longitudinal section of specimen Q (the udder), 8-10 cm long, as observed with the aid of specimen S (hand lens)

The drawing below is a fully-labelled longitudinal section of the udder. It is drawn in good proportion, with straight label lines touching each named part, and carries a title as required.

(d) Two economic uses of each of specimens O and P

Specimen O (feathers):

• Stuffing pillows, cushions and mattresses.
• Making feather meal used in livestock feeds.

Specimen P (hoof):

• Making glue/gum.
• Making buttons and ornaments.

(a) Brief description of the specimens:

• Specimen G (cutlass / matchet): a hand tool made of a long, broad, flat steel blade with a sharp cutting edge, fitted to a short wooden or plastic handle at one end.
• Specimen H (hoe): a hand tool made of a flat metal blade set almost at a right angle to a wooden handle; used for digging and working the soil.
• Specimen I (short-handle sickle): a hand tool with a short handle and a curved (crescent-shaped) steel blade whose inner edge is sharp; used for reaping.

(b) Two uses of each specimen:

(c) Three ways of maintaining the specimens:

1. Wash and clean the tools after use to remove soil and plant sap, then dry them to prevent rusting.
2. Sharpen the cutting edges regularly with a file or grinding stone to keep them effective.
3. Oil or grease the metal parts and store the tools in a cool, dry store, hanging them or standing them properly on a rack.

(a) One method of propagation for each specimen:

• Specimen J (yam tuber): vegetative propagation using yam setts (pieces cut from the tuber, or seed yams / minisetts).
• Specimen K (plantain): vegetative propagation using suckers (offshoots from the base of the mother plant); corms may also be used.
• Specimen L (tomato fruit): sexual propagation using the seeds extracted from the ripe fruit.

(b) Method of planting each specimen:

Specimen J (yam): The tuber is cut into setts, each carrying a portion of skin and a bud. The cut surfaces are treated (dusted with wood ash) and allowed to dry. Ridges or mounds/heaps are made, and each sett is planted about 8 to 10 cm deep, with the cut surface facing downwards, at a spacing of about 1 m by 1 m. The mounds are then mulched.

Specimen K (plantain): Healthy suckers (preferably sword suckers) are detached from the mother plant with a portion of the corm. Planting holes about 30 cm deep are dug at a spacing of about 3 m by 3 m. A sucker is placed upright in each hole, the corm is covered with topsoil, firmed and mulched.

Specimen L (tomato): Ripe fruits are cut and the seeds extracted, washed and dried. The seeds are first sown in a nursery bed or seed box by drilling in shallow rows and lightly covered with fine soil, then watered. After about 3 to 4 weeks the seedlings are transplanted to the field at a spacing of about 60 cm by 45 cm.