WAEC SSCE - Agricultural Science - 2019 (Essay)

Détails de la réponse

(a) Completed weed table:

Weed	Botanical name	Method of dispersal
Goat weed	Ageratum conyzoides	Wind
Siam weed	Chromolaena odorata	Wind
Water leaf	Talinum triangulare	Explosive mechanism (self-dispersal of the ripe capsule)

(b) Factors affecting land availability for agriculture:

(i) Physical factors:

1. Relief (topography) of the land.
2. Climate (rainfall and temperature).
3. Soil type and fertility.

(ii) Economic factors:

1. The land tenure system.
2. Availability of capital and the cost of land.
3. Access to markets and transport (and government policy).

(c) Four effects of pollution on agricultural lands and ponds:

1. It kills beneficial soil organisms and reduces soil fertility.
2. It contaminates the soil and water with toxic chemicals.
3. It kills fish and other aquatic life through oxygen depletion (eutrophication).
4. Toxins build up in crops and fish, making them harmful to consumers.

(d) Two ways of minimizing land and pond pollution:

1. Treat and properly dispose of industrial and domestic waste before it is discharged.
2. Use agrochemicals (fertilizers and pesticides) judiciously and only at recommended rates.

Détails de la réponse

The three crops shown in the diagram are Cashew (nut with its swollen pseudo-fruit or cashew apple), Oil palm (fruit shown in cross-section revealing the mesocarp, shell and kernel) and Okro (the elongated ridged seed pod).

a) Method of propagating each crop

Crop	Method of propagation
Cashew	Propagated sexually by seed (the nut). It may also be propagated vegetatively by grafting or budding for improved varieties.
Oil palm	Propagated sexually by seed (the kernel/nut), usually raised as pre-germinated seed in a nursery before transplanting.
Okro	Propagated sexually by seed, sown directly in the field.

b) Three varieties of oil palm

• Dura (thick shell, thin mesocarp)
• Tenera (thin shell, thick mesocarp; the high-yielding commercial hybrid)
• Pisifera (shell-less, female-sterile; used as a pollen parent)

Other recognised types include Macrocarya (very thick shell).

c) Three diseases of okro

• Okro mosaic (leaf curl) disease, caused by a virus
• Cercospora leaf spot, caused by a fungus
• Fusarium wilt, caused by a soil-borne fungus

Powdery mildew and damping-off are also common okro diseases.

d) Three pre-planting operations in cultivating okro

• Land clearing to remove weeds, shrubs and debris from the site
• Ploughing, harrowing and ridging (tillage) to produce a fine, well-aerated seedbed
• Seed treatment/selection, that is selecting viable seeds and dressing them against soil pests and diseases before sowing

Other acceptable pre-planting operations are soil testing and the application of organic manure/basal fertiliser.

e) Three uses of cashew

• The cashew nut (kernel) is eaten as food, either raw, roasted or salted, and is a source of edible oil.
• The cashew apple (pseudo-fruit) is eaten fresh or processed into juice, jam and alcoholic/soft drinks.
• The nut-shell liquid is used industrially in the manufacture of paints, varnishes, brake linings and insecticides; the tree also yields timber and gum, and serves as a shade/ornamental and soil-conservation plant.

Détails de la réponse

(a) Depreciation in agricultural production

Depreciation is the gradual reduction or loss in the value of a durable (fixed) farm asset such as machinery or a building over time, due to wear and tear, age, or obsolescence.

(b) Distinguish between the pairs of terms

(i) Farm records and farm accounts

Farm records	Farm accounts
Written information on all activities and events on the farm (operations, dates, inputs, outputs).	The part of the records dealing only with money matters (income and expenditure) to show profit or loss.

(ii) Credit and subsidy

Credit	Subsidy
A loan of money or inputs given to a farmer that must be repaid, usually with interest.	Financial or material aid given by government to reduce the farmer's cost of production, and it is not repaid.

(iii) Assets and liabilities

Assets	Liabilities
The properties and things of value owned by the farmer (land, machinery, livestock, cash).	The debts and money the farmer owes to others.

(c) Five problems of agricultural extension in West Africa

1. Inadequate funding of extension services.
2. Inadequate and poorly trained extension agents.
3. Poor transportation and inaccessible rural roads.
4. High level of illiteracy among farmers.
5. Wide farmer-to-agent ratio, so agents cannot reach all farmers.

(d) Five factors that affect the supply of cassava

1. Price of cassava.
2. Cost of production (inputs and labour).
3. Weather and climatic conditions.
4. Incidence of pests and diseases.
5. Government policy and the number of cassava farmers.

Détails de la réponse

(a) Explanation of terms

• (i) Flushing: The practice of giving breeding females extra, high-quality feed a few weeks before and during mating to improve ovulation and conception.
• (ii) Castration: The removal or destruction of the testes of a male animal to prevent it from breeding.
• (iii) Culling: The removal of old, sick, unproductive or undesirable animals from a herd or flock.

(b) Two advantages of each

(i) Flushing

1. It increases the ovulation rate, giving more offspring (twinning).
2. It improves the body condition and conception rate of the breeding female.

(ii) Castration

1. It makes the animal docile and easy to handle.
2. It improves meat quality (tender meat without odour) and prevents unwanted mating.

(iii) Culling

1. It removes unproductive animals and cuts feeding costs.
2. It improves the general quality of the herd and provides income from animals sold.

(c) Two uses of each survey equipment

(i) Prismatic compass

1. To measure the bearings or directions of survey lines.
2. To measure horizontal angles during traversing.

(ii) Measuring tape

1. To measure distances and lengths on the field.
2. To measure the boundaries and offsets of a piece of land.

(d) Floriculture and aquaculture differentiated

Floriculture is the cultivation of flowers and ornamental plants, while aquaculture is the rearing or cultivation of aquatic organisms such as fish in water bodies or ponds.

Détails de la réponse

The specimen shows a cocoa pod bearing dark, spreading rot patches, the symptoms of black pod disease.

(a)(i) Disease associated with the observed symptoms

Black pod disease of cocoa (caused by the fungus Phytophthora).

(a)(ii) Three ways of controlling the disease

1. Remove and destroy all infected pods promptly.
2. Prune the lower branches and canopy and weed regularly to reduce humidity around the trees.
3. Apply the recommended fungicide (for example a copper-based fungicide).

(b)(i) Three pests of cocoa

1. Cocoa capsids/mirids.
2. Mealy bugs.
3. Termites (stem borers and shield bugs also attack cocoa).

(b)(ii) Three ways of controlling the pests

1. Spray the trees with the appropriate insecticides.
2. Weed regularly and practise early harvesting to reduce pest breeding sites.
3. Use resistant crop varieties.

(c) Five factors to be considered in siting a crop farm

1. Soil fertility and soil type.
2. Topography of the land.
3. Accessibility and nearness to a good road.
4. Proximity to a source of water.
5. Proximity to the market (availability and cost of labour is also considered).

(d) Three ways of maintaining survey equipment

1. Clean or wash and dry it properly after use before storage.
2. Grease or oil the metal parts to prevent rust, and paint them when necessary.
3. Store it in a cool, dry place and keep the prismatic compass away from magnetic fields.

Détails de la réponse

(a) Explanation of terms

• Malnutrition: A condition that results from feeding an animal with a diet that is deficient, unbalanced, or in excess of one or more nutrients.
• Weaning: The gradual process of separating a young animal from its mother and changing it from a milk diet to solid feed.
• Heat period: The period (oestrus) during which the female animal is sexually receptive and ready to accept the male for mating.
• Candling: Passing an egg over or before a source of light in a dark room to examine its internal quality, fertility or stage of development.

(b) Maintenance ration and production ration distinguished

Maintenance ration	Production ration
The feed given to keep an animal alive and healthy, with no gain or loss in weight and no production.	The extra feed given, in addition to the maintenance ration, to enable the animal to produce milk, eggs, meat, work or offspring.

(c) Three effects of malnutrition on farm animals

1. It causes retarded or stunted growth.
2. It lowers productivity (less milk, eggs and meat) and causes poor reproduction.
3. It makes animals weak and more susceptible to diseases, and may cause death.

(d) Five effects of deforestation

1. It leads to soil erosion.
2. It causes loss of soil fertility.
3. It can lead to desertification.
4. It destroys the habitat of wildlife and reduces biodiversity.
5. It reduces rainfall and contributes to climate change and flooding.

Détails de la réponse

(a) Identification of the implement

The implement illustrated is a cultivator (a tractor-drawn tine cultivator). It is recognised by its rigid frame carrying several curved tines that end in narrow shares, mounted on a wheeled frame with a hitch for attachment to a tractor.

(a)(ii) Names of the labelled parts

Label	Name of part
I	Frame (main beam)
II	Clamp / tine bracket
III	Tine (shank)
IV	Share (point / shovel)

(b) One function of each labelled part

• I - Frame: It provides the rigid structure that holds and supports the tines, clamps and wheel firmly together.
• II - Clamp / bracket: It fastens each tine securely to the frame and allows the tine to be adjusted or replaced.
• III - Tine (shank): It penetrates the soil and carries the share, stirring and loosening the soil as the implement is drawn forward.
• IV - Share (point): It is the working edge that cuts into and breaks up the soil, uprooting weeds and forming a fine tilth.

(c) Farm operation

The cultivator is used for secondary tillage (cultivation): loosening and stirring the soil, breaking clods, uprooting and controlling weeds after primary ploughing, and preparing a fine seedbed.

(d) Two farm tools that perform similar functions

• West African hoe (used to loosen soil and weed)
• Hand fork / hand cultivator (used to stir and loosen soil)

(The harrow and the spade also perform comparable soil-loosening functions.)

(e) Three ways of maintaining the implement

1. Clean off soil and plant debris after every use and store it in a dry shed to prevent rust.
2. Oil or grease the wheel bearings and moving joints, and tighten any loose bolts and clamps regularly.
3. Sharpen blunt shares and replace worn or broken tines, and paint the frame to protect it from corrosion.

Détails de la réponse

(a) Spacing and thinning distinguished

Spacing	Thinning
The recommended distance left between one stand (and one row) and another at the time of planting.	The removal of excess seedlings from a stand after germination, leaving the required number of healthy plants.

(b) Cultivation of oil palm

• (i) Botanical name: Elaeis guineensis.
• (ii) Two varieties: Dura and Tenera.
• (iii) Method of propagation: By seed (sexual). Pre-germinated seeds are raised in a pre-nursery and nursery before the seedlings are transplanted to the field.
• (iv) Soil requirement: Deep, well-drained, fertile loamy soil that is rich in organic matter and slightly acidic.
• (v) Spacing on the field: About 9 m by 9 m triangular (giving roughly 143 palms per hectare).
• (vi) Diseases: Blast disease, freckle/leaf spot, and vascular (Fusarium) wilt.

(c) Six ways forest resources are important to the economy of West Africa

1. They supply timber for building and furniture.
2. They provide fuel wood and charcoal.
3. They supply raw materials for industries (pulp, paper).
4. They provide employment and income.
5. They are a source of medicinal plants and food (fruits, bush meat).
6. They earn foreign exchange through export of forest products.

(d) Apiculture

Apiculture is the practice of keeping and rearing honey bees in hives for the production of honey and beeswax.

Détails de la réponse

(a) Identification of the parasites

• I: Louse (an ecto-parasite)
• II: Tapeworm (an endo-parasite)

(b) Three external features of parasite I (Louse)

1. A distinct head, thorax and segmented abdomen.
2. Three pairs (six) of legs bearing sharp claws for clinging to the host.
3. A pair of antennae, a pair of compound eyes and biting-and-sucking mouthparts.

(c) Part of the host where parasite II (Tapeworm) is found

It is found in the small intestine of the host.

(c)(i) Four adaptive features of parasite II (Tapeworm) on its host

1. It possesses four suckers with which it attaches itself to the wall of the host's intestine.
2. It possesses two rows of hooks (rostellum) with which it fixes itself firmly in the intestine.
3. Its whole body is covered with a resistant cuticle that prevents it from being digested by the host's enzymes.
4. It has no digestive system of its own and absorbs digested food over its entire body, its great length providing a large surface area for absorption.

(c)(ii) Two intermediate hosts of parasite II (Tapeworm)

1. Cattle
2. Pigs

(d) Three effects of parasite I (Louse) on its host

1. It causes skin irritation, making the host restless, and leads to loss of hair or feathers.
2. It sucks the host's blood, leading to anaemia, loss of appetite and loss of weight.
3. The injuries it causes serve as sites for secondary infection, reducing livestock production and, in severe cases, causing death.

(e) Three effects of parasite II (Tapeworm) on its host

1. It robs the host of digested food, causing loss of weight, weakness and reduced production.
2. When present in large numbers it may block the intestine.
3. It releases toxins that make the host unthrifty and unproductive.

Détails de la réponse

(a)(i) Drainage is the removal of excess (gravitational) water from the surface and sub-surface of the soil so that the soil remains well aerated and workable.

(a)(ii) Reasons why waterlogged agricultural land should be drained:

1. To improve soil aeration so that plant roots and soil organisms can respire.
2. To raise soil temperature, which encourages seed germination and root growth.
3. To improve soil structure and workability, allowing tillage and machinery movement.
4. To remove toxic substances and prevent root-rot diseases, encouraging deeper rooting.

(b) Six factors affecting nutrient availability in the soil:

1. Soil pH (soil reaction).
2. Soil texture and structure.
3. Organic matter (humus) content.
4. Soil moisture content.
5. Soil temperature.
6. Activity of soil micro-organisms.

(c) Causative organisms of the crop diseases:

Disease	Causative organism
Rice blast	(i) Pyricularia oryzae (a fungus)
Groundnut rosette	(ii) Groundnut rosette virus
Cassava mosaic	(iii) Cassava mosaic virus (a geminivirus)
Root knot of tomato	(iv) Meloidogyne species (root-knot nematode)
Maize rust	(v) Puccinia species (a fungus)
Tristeza	(vi) Citrus tristeza virus

Détails de la réponse

(a) Full meaning of the acronyms

• (i) WARDA: West Africa Rice Development Association
• (ii) IITA: International Institute of Tropical Agriculture
• (iii) FAO: Food and Agriculture Organization (of the United Nations)
• (iv) ILCA: International Livestock Centre for Africa

(b) Six ways agriculture benefits rural communities

1. It provides food for the rural people.
2. It provides employment and keeps people busy.
3. It is a source of income to the farmers.
4. It supplies raw materials for local rural industries.
5. It attracts the provision of infrastructure such as roads, water and electricity.
6. It reduces rural-to-urban migration by keeping people on the land.

(c) Four liming materials used in agriculture

1. Limestone (calcium carbonate)
2. Quicklime (calcium oxide)
3. Slaked or hydrated lime (calcium hydroxide)
4. Wood ash

(d) Four examples of sedimentary rocks

1. Limestone
2. Sandstone
3. Shale
4. Conglomerate

Détails de la réponse

(a) Four roles of government in agricultural development

(i) Pest and disease control

• Establishing quarantine services to check the movement and spread of pests and diseases.
• Providing and subsidising agrochemicals, spraying equipment and free vaccination, and carrying out research into control measures.

(ii) Marketing of agricultural produce

• Setting up marketing boards and providing storage facilities to reduce wastage.
• Building good roads for transport and guaranteeing stable, minimum prices for produce.

(b) Four general problems of the land tenure system in West Africa

1. Fragmentation of land into small, scattered units that cannot be mechanised.
2. Land held by inheritance and communal ownership discourages large-scale farming.
3. Difficulty in acquiring enough land for expansion, worsened by disputes and litigation.
4. Insecurity of tenure discourages tenants from making permanent improvements, and land is hard to use as loan collateral.

(c) Three farm machinery and three farm implements

Farm machinery:

1. Tractor
2. Combine harvester
3. Milking machine

Farm implements:

1. Plough
2. Harrow
3. Ridger

Détails de la réponse

The set-up is a soil sedimentation (mechanical analysis) experiment. Soil has been shaken with water in a tall transparent cylinder and left to stand. Because particles settle in order of size and density, the largest and heaviest fall first and the finest settle last, so the material grades from coarse at the bottom to fine at the top, with organic matter floating on the water surface.

(a)(i) Aim of the experiment

To separate a soil sample into its constituent fractions (gravel, sand, silt, clay and organic matter) according to particle size, and so to determine the texture and composition of the soil by sedimentation.

(a)(ii) Parts labelled I and II

The pointers pick out the two fine bands lying just under the floating organic matter and the clear water, above the coarser sand and gravel at the base. In a settled column the finest fraction rests highest:

• I = Clay (the finest particles, still partly in suspension, forming the uppermost, densely stippled band of settled sediment just below the water).
• II = Silt (the next, slightly coarser band lying directly beneath the clay).

For orientation: the wispy material floating on the surface is decayed organic matter (humus), and below silt lie sand and then gravel/stones at the very base.

(b) How the experiment is carried out

1. Take a sample of dry, crushed soil and pick out large roots and stones.
2. Put the soil into a tall transparent glass jar or measuring cylinder until it is about one-third full.
3. Add clean water (and a little dispersing agent such as sodium carbonate or caustic soda) until the jar is about three-quarters full.
4. Cover the mouth and shake vigorously so that all the clods break up and every particle is suspended in the water.
5. Stand the jar on a level bench and leave it undisturbed for about an hour (or longer).
6. Observe the layers as they settle: gravel and stones at the bottom, then sand, then silt, then clay, with humus floating on top and the water clearing above.
7. Measure the depth of each layer and express it as a percentage of the total settled soil to estimate the proportion of each fraction. For example, if sand is \(4\ \text{cm}\) of a total \(10\ \text{cm}\) of settled soil, \(\dfrac{4}{10}\times 100\% = 40\%\).

(c) Four properties of sandy soils

1. Large particles with wide pore spaces, giving very good aeration and free (rapid) drainage.
2. Low water-holding capacity, so the soil dries out quickly and needs frequent watering.
3. Poor in plant nutrients and low in humus, and nutrients are easily leached (washed) out.
4. Light, loose and gritty; it warms up quickly and is easy to till.

(d) Test for soil acidity using litmus paper

1. Put a little of the soil sample into a clean test tube or beaker.
2. Add distilled (or rain) water, stir well to make a suspension, and allow it to settle so a clear solution forms above the soil.
3. Dip a strip of blue litmus paper into the clear liquid; test a fresh portion with red litmus paper as well.
4. If the blue litmus paper turns red, the soil is acidic. If red litmus turns blue, the soil is alkaline (basic); if neither paper changes colour, the soil is neutral.

Détails de la réponse

(a) Classification of the crops by life cycle:

Crop	Classification (life cycle)
Mango	Perennial
Rice	Annual
Groundnut	Annual
Cotton	Annual
Pepper	Biennial
Soya bean	Annual
Oil palm	Perennial
Yam	Annual
Tomato	Annual
Rubber	Perennial
Ginger	Biennial
Cocoa	Perennial
Cowpea	Annual
Carrot	Biennial

(b) Four components of a typical soil and their percentage volume:

Soil component	Percentage volume
(i) Mineral matter	45%
(ii) Organic matter	5%
(iii) Soil water	25%
(iv) Soil air	25%

(c) Three methods of applying inorganic fertilizers:

1. Broadcasting (spreading it evenly over the field).
2. Band or ring placement (in bands or rings near the plants).
3. Side dressing or top dressing along the crop rows.

Détails de la réponse

(a) Calculations

Cost of tractor in 2000 = D 12,000.00; sold in 2009 for D 3,000.00.

(i) Useful life

\[ \text{Useful life} = 2009 - 2000 = 9\ \text{years} \]

(ii) Salvage value

The salvage value is the amount realised on disposal = D 3,000.00.

(iii) Total depreciation

\[ \text{Total depreciation} = \text{Cost} - \text{Salvage value} = 12{,}000 - 3{,}000 = D\ 9{,}000.00 \]

(iv) Annual depreciation

\[ \text{Annual depreciation} = \frac{\text{Total depreciation}}{\text{Useful life}} = \frac{9{,}000}{9} = D\ 1{,}000.00\ \text{per year} \]

(b) Description of terms

• (i) Demand schedule: A table showing the various quantities of a commodity that consumers are willing and able to buy at different prices over a period of time.
• (ii) Supply curve: A graph showing the relationship between price and quantity supplied; it slopes upward from left to right, showing that more is supplied at higher prices.

(c) Four agricultural extension agencies in West Africa

1. Agricultural Development Project (ADP)
2. Ministry of Agriculture
3. Agricultural research institutes
4. Farmers' cooperative societies

(d) Four ways soils are enriched with nitrogen

1. Growing leguminous crops that fix atmospheric nitrogen through Rhizobium bacteria.
2. Application of nitrogenous fertilizers.
3. Application of organic manure and green manuring.
4. Fixation of atmospheric nitrogen by lightning during rainfall.

Détails de la réponse

(a)(i) Intensive system and extensive system distinguished

Intensive system	Extensive system
Animals are confined (housed) on a small area of land.	Animals roam and graze freely over a large area of land.
High capital, labour and feed input per animal; high productivity.	Low capital, labour and feed input; lower productivity.

(a)(ii) Five disadvantages of keeping livestock on free-range (extensive) system

1. Animals are exposed to attack by predators.
2. They are easily exposed to diseases and parasites.
3. Breeding cannot be controlled, leading to indiscriminate mating.
4. Growth is slow because feeding is inadequate and irregular.
5. Animals are difficult to supervise and are easily stolen.

(b) Six ways in which ornamental plants are important

1. They beautify and decorate the environment.
2. They provide shade.
3. They serve as windbreaks.
4. They help to check soil erosion.
5. They purify the air by giving out oxygen.
6. They are a source of income when sold and are used for landscaping.