WAEC SSCE - Agricultural Science - 2009 (Essay)

Détails de la réponse

(a) Four soil conservation practices to control erosion on a gentle slope

• Contour ploughing/cultivation.
• Cover cropping (and mulching).
• Strip cropping.
• Crop rotation (and afforestation/planting cover vegetation).

(b) How each practice conserves the soil

• Contour ploughing: The ridges and furrows are made across the slope (along the contour). They act as barriers that trap running water, slow it down and encourage it to soak into the soil instead of washing the topsoil away.
• Cover cropping/mulching: The cover crop or mulch shields the soil surface from the direct impact of raindrops, reduces the speed of run-off, holds the soil particles together with roots and adds organic matter that improves soil structure and water retention.
• Strip cropping: Erosion-permitting crops (row crops) are alternated in strips with close-growing, soil-protecting crops across the slope. The protective strips slow down run-off and trap soil washed from the open strips, reducing the total soil lost.
• Crop rotation: Growing different crops, including cover/leguminous crops, in sequence keeps the ground continuously covered, improves soil structure and organic matter, and reduces the exposure and loss of bare soil to erosion.

Détails de la réponse

(a) Four characteristics of clay

• It has very fine particles (less than 0.002 mm).
• It has high water-holding capacity and drains poorly (poor aeration).
• It is sticky and plastic when wet, and hard/cracks when dry.
• It is heavy to work (heavy soil) and generally high in nutrients (high cation exchange capacity).

(b) Four effects of drought on plant growth and development

• Wilting and eventual death of plants.
• Stunted growth and reduced yield.
• Shedding of leaves, flowers and fruits (premature ripening).
• Reduced germination and poor nutrient uptake (nutrients cannot dissolve without water).

(c) Two symptoms of phosphorus deficiency in crops

• Purplish/reddish colouration of the leaves and stem.
• Stunted growth with poor root development and delayed maturity.

(d) Importance of soil properties in crop production

(i) Soil reaction (pH):

• It determines the availability of plant nutrients in the soil.
• It affects the activity of soil micro-organisms (for example nitrogen-fixing bacteria).
• It influences which crops can grow well, since crops have preferred pH ranges.

(ii) Soil temperature:

• It affects the rate and speed of seed germination.
• It influences the rate of root growth and nutrient/water absorption.
• It affects the activity of soil micro-organisms and the rate of decomposition of organic matter.

Détails de la réponse

(a) Six factors that limit food production in West Africa

• Inadequate finance/capital and credit for farmers.
• Use of poor tools and low level of mechanisation.
• Pests and diseases of crops and livestock.
• Unfavourable/unreliable climate (drought, erratic rainfall).
• Poor storage, processing and transport facilities leading to high losses.
• Poor/infertile soils, land tenure problems, and inadequate improved inputs (seeds, fertilizer).

(b) Solar energy as a source of farm power

Three advantages:

• It is free, renewable and inexhaustible once the equipment is installed.
• It is clean and does not pollute the environment.
• It requires little maintenance and can be used in remote areas without a power grid.

Three disadvantages:

• It is not available at night and is unreliable on cloudy/rainy days.
• The initial cost of the equipment (panels, batteries) is high.
• It produces relatively small amounts of power and requires storage (batteries) for continuous use.

(c) Four tractor-coupled implements

• Plough.
• Harrow.
• Ridger.
• Planter (also harvester/trailer).

Détails de la réponse

(a)(i) Meaning of culling in poultry production [2 marks]

Culling is the deliberate removal (selecting out and disposing of) of undesirable, unproductive, sick, weak or old birds from a flock in order to keep only the healthy and productive stock.

(a)(ii) Three benefits derived from culling [3 marks]

• It removes unproductive birds, so feed is not wasted on non-layers and cost of production is reduced.
• It removes sick and weak birds, thereby checking the spread of diseases and parasites in the flock.
• It improves the overall quality and productivity of the flock, raising average egg or meat output.

(b) Four ways of preventing diseases in a sheep flock [4 marks]

• Vaccinate the sheep regularly against common diseases such as PPR (peste des petits ruminants).
• Provide clean feed, clean drinking water and good sanitation in the pen.
• Deworm the flock routinely and dip or spray them to control external parasites (ticks, lice).
• Isolate (quarantine) newly bought or sick animals to prevent the introduction and spread of disease.

(c) Paddocking as a way of improving rangeland [4 marks]

Paddocking is the division of a large range or pasture into smaller fenced units called paddocks so that animals can be grazed in one paddock at a time while the others rest and regrow. By rotating the animals from paddock to paddock, the grasses are not overgrazed and are given time to recover and re-establish, which maintains a good stand of nutritious forage. It allows even utilisation of the pasture, prevents selective grazing and trampling, permits the resting paddocks to be treated (reseeded, fertilised or weeded), helps to break the life cycle of internal parasites, and makes it easier to manage and control the movement of the herd. Overall, paddocking increases the carrying capacity and productivity of the rangeland.

(d) Three fishery regulations [3 marks]

• Prohibition of the use of harmful fishing methods such as chemicals, explosives (dynamite) and poisons.
• Use of nets with an approved (large) mesh size so that young/immature fish are not caught.
• Observance of a closed season and licensing of fishermen to prevent over-fishing and protect breeding stock.

Détails de la réponse

(a)(i) What is an agricultural system?

An agricultural system is a particular method or pattern of organising and carrying out farming activities (the way crops are grown and/or animals are reared) on a piece of land to achieve production goals.

(a)(ii) Five agricultural systems practised in West Africa

• Shifting cultivation.
• Bush fallowing (land rotation).
• Mixed farming (crops and livestock together).
• Mixed cropping.
• Continuous cropping / plantation (monocropping) system.

(b) Four ways NGOs contribute to agricultural production

• They provide credit, grants and farm inputs to farmers.
• They train farmers and provide extension education.
• They fund and carry out agricultural research.
• They help provide rural infrastructure and market outlets for produce.

(c) One function of each incubator component

• (i) Counter: records/keeps track of the number of days (turns) the eggs have been incubated.
• (ii) Thermostat: automatically regulates and maintains the correct temperature inside the incubator.
• (iii) Hygrometer: measures the relative humidity (moisture content) inside the incubator.
• (iv) Egg tray: holds/supports the eggs in position (and aids turning) during incubation.
• (v) Heater: supplies the heat needed to keep the eggs warm for the embryos to develop.

Détails de la réponse

(a)(i) Meaning of marketing channel [2 marks]

A marketing channel is the path or chain of intermediaries (middlemen) through which agricultural produce passes from the producer (farmer) to the final consumer.

(a)(ii) Marketing channels for cocoa [4 marks]

A typical channel for cocoa is:

Farmer (producer) → local buying agent/village assembler → licensed buying agent/commodity board → wholesaler/exporter → processor/overseas manufacturer → final consumer.

In short form: Producer → Middlemen (agents and licensed buyers) → Marketing board/exporter → Processor → Consumer.

(b) Three characteristics of land [3 marks]

• Land is a free gift of nature (it is not produced by man).
• Land is fixed in supply (its total quantity cannot be increased or decreased).
• Land is immobile (it cannot be moved from one location to another).

(c) Three agricultural extension programmes in West Africa [3 marks]

• Agricultural Development Projects (ADPs).
• Farm Settlement Schemes.
• Operation Feed the Nation (OFN) / Green Revolution programme.

(d) Four advantages of demonstration as an extension teaching method [4 marks]

• It shows farmers practically how a new practice is carried out, so learning is by seeing and doing.
• Results seen with the eyes convince farmers more easily and encourage quick adoption.
• It builds the confidence and skill of farmers in the new technique.
• It is suitable for illiterate farmers because it depends on demonstration rather than reading.

Détails de la réponse

(a)(i) Definition of brooder

A brooder is a specially heated house or equipment used to provide artificial warmth and care for day-old chicks in the absence of a mother hen, until they can regulate their own body temperature.

(a)(ii) Four characteristics of a good layer

• A bright red, well developed comb and wattles.
• A large, soft and moist vent.
• Wide spacing (three to four fingers) between the pelvic bones.
• Alert and active with bleached (pale) shanks and beak from continuous laying.

(b) Four reasons for providing suitable housing for livestock

• To protect the animals from harsh weather (rain, sun, cold, wind).
• To protect them from predators and thieves.
• To make feeding, watering, management and disease control easy.
• To provide comfort and reduce stress, thereby improving growth and production.

(c) Scientific names of three fish species commonly stocked in a pond

• Oreochromis niloticus (tilapia).
• Clarias gariepinus (African catfish).
• Heterotis niloticus (also Heterobranchus species).

(d) Three qualities of a good pasture plant

• It should be highly palatable and nutritious (high protein).
• It should be fast growing and produce high yield of herbage.
• It should be persistent, drought tolerant and able to withstand repeated grazing/trampling.

Détails de la réponse

(a)(i) What is an inventory record? [2 marks]

An inventory record is a written and up-to-date list showing all the assets and property of a farm (land, buildings, machinery, tools, livestock, stored produce, inputs, etc.), together with their quantities and money value at a particular date.

(a)(ii) Four steps involved in taking inventory [4 marks]

1. Listing (identifying and writing down) all the items and property found on the farm.
2. Counting or measuring each item to determine its quantity.
3. Valuing each item by attaching a current money value to it.
4. Recording and totalling the values to obtain the overall worth of the farm assets.

(a)(iii) Two ways inventory record is important in farm business [2 marks]

• It shows the true worth (net worth) of the farm and is used in preparing the balance sheet.
• It helps in obtaining loans and credit because it serves as evidence of the assets available as security.

(b) Four objectives of agricultural extension [4 marks]

• To teach farmers improved and modern farming practices and techniques.
• To raise the standard of living and income of rural farmers.
• To help farmers identify and solve their own farming problems.
• To pass research findings and innovations from research stations to the farmers.

(c) Extension teaching methods [4 marks]

(i) News bulletin: This is a printed sheet or short broadcast that carries up-to-date farming information, announcements and advice to many farmers at the same time. It is used to give timely reports on prices, new inputs, weather and events, spreading information quickly and cheaply over a wide area.

(ii) Agricultural shows: These are organised exhibitions where farmers, research bodies and companies display improved crops, livestock, tools and produce. They allow farmers to see new varieties, breeds and machines, compare results, exchange ideas, and are motivated (through prizes and competition) to adopt improved practices.

Détails de la réponse

(a) Four aims of crop improvement

• To develop high-yielding varieties.
• To develop varieties resistant to pests and diseases.
• To produce early-maturing varieties.
• To improve the quality of produce and develop varieties tolerant of adverse conditions (drought, poor soils).

(b) Four conditions necessary for seed germination

• Adequate water (moisture).
• Suitable/warm temperature.
• Oxygen (air).
• Viable seed (and, for some seeds, light).

(c) Importance of conducting a germination test

It is done to determine the viability (percentage germination) of the seeds, so that the farmer knows the quality of the seed and can decide the correct seed rate to plant and avoid wasting time and land on seeds that will not germinate.

(d) Three problems associated with poor quality planting materials

• Poor germination: low-viability seeds give patchy, uneven stands and gaps in the field, reducing plant population.
• Low yield: weak or unimproved materials produce sickly plants that give poor yields and low-quality produce.
• Disease and pest carry-over: infected planting materials introduce and spread pests and diseases into the field, causing further crop losses.

Détails de la réponse

Production of cocoa (Theobroma cacao)

(a) Land preparation

The land is cleared, with some tall forest trees deliberately left or shade trees planted to provide shade for the young cocoa. The undergrowth is slashed and the debris packed, avoiding complete clearing so that the soil and young seedlings are protected. Planting holes are then dug and lined out.

(b) Climatic requirements

• High rainfall of about 1,000 mm to 2,000 mm, well distributed through the year.
• Warm temperature of about 21 to 32 degrees Celsius.
• High relative humidity and shade, sheltered from strong winds.

(c) Planting

• Cocoa is first raised in a nursery from seeds (pods), usually in polythene bags under shade, for about four to six months.
• Seedlings are hardened off and transplanted to the field at the onset of the rains.
• Planting is done at a spacing of about 3 m x 3 m (roughly 1,100 stands per hectare) under temporary/permanent shade.
• The seedlings are planted carefully into the prepared holes, watered and mulched to establish them.

(d) One disease of cocoa

Black pod disease, caused by the fungus Phytophthora palmivora. It causes black or brown spots that spread over the pods, rotting them, and can be controlled by regular harvesting, removal/burning of infected pods and spraying with a copper-based fungicide (for example Bordeaux mixture).