WAEC SSCE - Agricultural Science - 2012 (Practical)

Maelezo ya Majibu

(a) Identification of specimens

• Specimen H: cutlass (machete).
• Specimen I: hoe.
• Specimen J: shears.
• Specimen K: rake.
• Specimen L: watering can.
• Specimen M: shovel.

(b) One major use of each specimen

• Specimen H (cutlass): for clearing and slashing bushes and weeds.
• Specimen I (hoe): for making ridges and seedbeds.
• Specimen J (shears): for trimming hedges and pruning branches.
• Specimen K (rake): for gathering rubbish and levelling the soil surface.
• Specimen L (watering can): for supplying water to young seedlings in the nursery.
• Specimen M (shovel): for transferring soil from one place to another.

(c) Three general maintenance practices for specimens H (cutlass), J (shears) and M (shovel)

• Clean, wash and dry them after every use.
• Sharpen the cutting blades and oil the metal parts and joints before storage to prevent rust.
• Tighten loose joints, replace worn parts, and store them in a cool dry place away from termites.

(d) One tractor-coupled implement performing similar functions

• Specimen H (cutlass): slasher (lawn mower).
• Specimen I (hoe): ridger or mouldboard/disc plough.
• Specimen K (rake): harrow.

Maelezo ya Majibu

(a)(i) Examples of the specimens (specimen A being an organic manure and specimen B an inorganic fertilizer):

• Specimen A (organic manure): poultry droppings and cow dung (also compost or green manure).
• Specimen B (inorganic fertilizer): NPK 15:15:15 and urea (also sulphate of ammonia or single superphosphate).

(a)(ii) Three advantages of applying specimen A (organic manure) in crop production:

1. It improves soil structure and increases the water-holding capacity of the soil.
2. It adds humus and releases its nutrients slowly over a long period.
3. It improves soil aeration and encourages the activity of useful soil organisms.

(a)(iii) Two methods of applying specimen B (inorganic fertilizer):

1. Broadcasting (spreading it evenly over the field).
2. Band or ring placement near the plant (or foliar spraying of soluble types).

(b) Percentage of water in the soil samples. Working from the recorded masses:

(b)(i) Mass of fresh soil = (mass of crucible + fresh soil) - mass of crucible.

• Sample C = \( 100 - 80 = 20 \) g
• Sample D = \( 140 - 80 = 60 \) g

(b)(ii) Mass of water = (mass of crucible + fresh soil) - (mass of crucible + soil after heating), that is the loss on heating.

• Sample C = \( 100 - 95 = 5 \) g
• Sample D = \( 140 - 100 = 40 \) g

(b)(iii) Percentage of water \( = \dfrac{\text{mass of water}}{\text{mass of fresh soil}}\times100 \).

• Sample C \( = \dfrac{5}{20}\times100 = 25\% \)
• Sample D \( = \dfrac{40}{60}\times100 = 66.67\% \)

(c) There is an inverse (antagonistic) relationship between the amount of water and the amount of air in the soil: both share the same pore spaces, so as the water content rises the air content falls, and vice versa.

Maelezo ya Majibu

(a) Identification of the specimens

• Specimen N is groundnut seeds.
• Specimen O is maize grains.
• Specimen P is guinea corn (sorghum) grains.
• Specimen Q is the aphid.

(b) Plant population per hectare at a spacing of 60 cm x 25 cm

One hectare = 10,000 m². Converting the spacing to metres, 60 cm = 0.6 m and 25 cm = 0.25 m.

Area occupied by one plant = 0.6 m × 0.25 m = 0.15 m².

\[\text{Plant population} = \frac{\text{Area of land}}{\text{Area per plant}} = \frac{10000}{0.15} = 66\,667 \text{ plants per hectare.}\]

Since one seed of specimen N is sown per hole, the plant population is about 66,667 plants per hectare.

(c) Two reasons for including groundnut (the plant from which specimen N is obtained) in crop rotation

• Being a legume, it fixes atmospheric nitrogen in the soil through Rhizobium bacteria in its root nodules, thereby restoring and improving soil fertility.
• Its spreading, ground-covering growth smothers weeds and protects the soil surface, checking erosion.

(d) Three uses of specimen P (guinea corn/sorghum)

• It is used as food for human beings.
• It is used as feed for livestock and poultry.
• It is used in the production of local and alcoholic beverages; the stalks are also used for roofing, staking and as fuel.

(e) Two ways the activities of specimen Q (aphid) affect crops

• The aphids pierce the tender leaves, stems and pods and suck the plant sap, causing distortion of leaves, defoliation and reduced yield.
• They transmit viral diseases from plant to plant as they feed.

Maelezo ya Majibu

(a)(i) Identity of specimen R

Specimen R is a hurricane lamp (kerosene lantern / pressure lamp). It has the characteristic metal frame, a glass globe protecting a wick that burns kerosene, a fuel reservoir at the base and a wire carrying handle. In poultry management it serves as a source of heat and light for brooding young chicks.

(a)(ii) Two disadvantages of using specimen R in a poultry house

1. It is a fire hazard. The naked kerosene flame can easily ignite dry litter, feathers or wood shavings and burn down the poultry house.
2. It gives uneven and inadequate heat, so chicks tend to crowd towards it, leading to smothering, uneven growth and high chick mortality.

(Other acceptable points: it produces smoke and fumes such as carbon monoxide that suffocate birds; the temperature cannot be accurately regulated; it needs constant refuelling and attention.)

(a)(iii) Two precautions to be taken when using specimen R

1. Place it out of the reach of the birds and away from litter, curtains and other inflammable materials to prevent fire and burns.
2. Provide adequate ventilation in the house so that smoke and fumes escape and do not suffocate the birds.

(Also acceptable: do not overfill the reservoir; keep the wick trimmed and the globe clean; never refuel while it is burning; hang it securely so it cannot fall over.)

(a)(iv) Two ways of maintaining specimen R

1. Trim the wick regularly and clean the glass globe so that it burns brightly without soot.
2. Refill the reservoir with clean, good-quality kerosene and check for leaks so that it burns steadily.

(a)(v) Two devices that can be used in place of specimen R in a poultry house

1. Electric brooder (with heat/infra-red bulbs).
2. Gas brooder (gas-fired heater/canopy brooder).

(Also acceptable: charcoal stove/pot brooder, infra-red heat lamp.)

(b)(i) What the observed signs indicate

The reddened and swollen vulva, whitish mucus discharge, restlessness (undue noise) and mounting of one another show that the sows are on heat (in oestrus), that is, they are sexually receptive and ready to be served (mated).

(b)(ii) Expected farrowing date

The gestation (pregnancy) period of a pig is about 114 days (3 months, 3 weeks and 3 days). Counting 114 days from the service date of 1st March, 2012 (a leap year):

Day of service, 1st March, is day 61 of the year. Adding the gestation length:

\[ 61 + 114 = 175 \text{ (day of the year)} \]

Working the 114 days through the calendar:

Therefore the sow should be expected to farrow on 23rd June, 2012.

(b)(iii) Three preparations in the farrowing pen before the sow farrows

1. Clean and disinfect the farrowing pen and provide fresh, dry bedding (litter) to prevent infection.
2. Provide a source of warmth (heat lamp/brooder) and a creep/guard rail area for the piglets to protect them from cold and from being crushed by the sow.
3. Provide clean water and feed and have farrowing materials ready (clean towels, disinfectant, iodine for the navel, and equipment for any assistance needed at birth).