WAEC SSCE - Agricultural Science - 2004 (Essay)

Détails de la réponse

Practices in crop production

(a) Transplanting

Transplanting is the careful removal of young seedlings from the nursery (or seedbed) and replanting them in their permanent positions in the field. It is done when the seedlings are strong enough to survive on their own. It is best carried out in the evening or on a cloudy day and the seedlings are watered afterwards to reduce transplanting shock. It allows only healthy, vigorous seedlings to be selected, gives proper (uniform) spacing, and is used for crops such as tomato, pepper, rice and tobacco.

(b) Shading

Shading is the provision of shade (using palm fronds, mats, nets or grass) over a nursery or young transplanted seedlings to protect them from the direct heat of the sun, heavy rain and drying wind. It reduces excessive transpiration and wilting, keeps the soil moist and cool, and helps the tender seedlings to establish. Shade is gradually removed (hardening off) as the seedlings grow stronger.

(c) Supplying (filling-in)

Supplying, also called filling-in or beating up, is the replanting of seeds or seedlings in the spots (stands/hills) where the earlier planted ones failed to germinate or died. It is done soon after germination so that the new plants do not lag too far behind. It ensures a full and even plant population per unit area, thereby maintaining the expected yield.

(d) Nursery

A nursery is a specially prepared, well-protected small area of land (or containers/boxes) where seeds are first sown and the young seedlings are raised and tended until they are big enough to be transplanted to the field. It allows close attention, watering, shading and protection of the delicate seedlings, and permits selection of only the healthy ones for transplanting. It is used for crops with very small seeds or slow early growth, such as tomato, tobacco, oil palm and cocoa.

Détails de la réponse

(a) Eight reasons why agriculture has not been fully mechanized in West Africa [8 marks]

• Lack of adequate capital/finance to buy expensive machines.
• High cost of purchasing, running and maintaining farm machinery.
• Small and fragmented (scattered) farm holdings that machines cannot work economically.
• The land tenure system which makes it difficult to acquire large continuous farmland.
• Shortage of trained personnel (operators, mechanics) to handle and repair machines.
• Rough topography, presence of stumps, boulders and swampy soils that hinder machine use.
• Poor rural infrastructure, that is, bad roads and lack of spare parts and repair workshops.
• Illiteracy and conservatism of farmers who prefer traditional tools and methods.

(b) Four characteristics of each [8 marks]

(i) Subsistence agriculture:

• Production is mainly for the farmer and his family, with little for sale.
• Farm size (holding) is small.
• Simple hand tools such as hoes and cutlasses are used.
• Output/yield is low and family labour is used.

(ii) Commercial agriculture:

• Production is mainly for sale and profit.
• Large farm holdings are cultivated.
• Machines and modern inputs (fertilizers, improved seeds) are used.
• Output/yield is high and hired/skilled labour is employed.

Détails de la réponse

(a) Three major organs in each cavity [6 marks]

• Thoracic (chest) cavity: heart, lungs and the wind-pipe/oesophagus (also large blood vessels).
• Abdominal cavity: stomach, liver and intestines (also kidneys, spleen and pancreas).

(b) Functions of the nervous and reproductive systems [3 marks]

Two functions of the nervous system:

• It receives stimuli through sense organs and coordinates/controls the activities of the body.
• It transmits impulses (messages) and directs the response of the animal, controlling movement and involuntary body processes.

One function of the reproductive system:

• It produces sex cells (gametes) and enables the animal to reproduce and give rise to offspring, continuing the species.

(c) Importance of the following systems [importance]

• (i) Circulatory system: It transports digested food, oxygen, water and hormones to all body cells and carries away waste products (carbon dioxide, urea) to the excretory organs; it also distributes heat and helps defend the body against disease. Without it, cells would not be nourished or cleansed.
• (ii) Respiratory system: It takes in oxygen needed for the release of energy (respiration) in the cells and gives out carbon dioxide, a waste gas. This gaseous exchange keeps the animal alive and provides energy for growth, work and production.
• (iii) Digestive system: It breaks down (digests) the feed the animal eats into simple soluble substances that can be absorbed into the blood for growth, energy and body maintenance, and it removes the undigested waste. Good digestion means good use of feed and better production.

Détails de la réponse

(a) Four effects of feed shortage on animal production [4 marks]

• Stunted growth and loss of body weight in the animals.
• Reduced production of milk, eggs and meat (low productivity).
• Poor reproduction, that is, reduced fertility and low birth rate.
• Lowered resistance to diseases, weakness and, in severe cases, death of the animals.

(b) Four areas of specialisation in agriculture and two contributions of each [16 marks]

• Agronomy (crop production): It develops improved crop varieties and better cultivation practices; and it increases food and raw-material production for the nation.
• Animal husbandry (livestock production): It supplies meat, milk, eggs and other animal protein for good nutrition; and it provides raw materials (hides, skin) and improved breeds of livestock.
• Agricultural engineering: It designs and provides farm machines, tools and irrigation structures that mechanise farming; and it develops soil and water conservation and storage/processing facilities.
• Agricultural economics/extension: It teaches farmers improved methods and helps them market their produce profitably; and it guides farm planning, record keeping and efficient use of resources, raising farmers' income.

Détails de la réponse

(a) Two methods of calculating depreciation of farm machines [2 marks]

• Straight-line method (equal instalment method).
• Reducing (declining) balance method. (Others include the sum-of-the-years'-digits and revaluation methods.)

For example, by the straight-line method,

\[\text{Annual depreciation} = \frac{\text{Cost} - \text{Salvage value}}{\text{Estimated useful life (years)}}.\]

(b) Four roles of capital in agricultural production [4 marks]

• It is used to buy land, machinery, tools and farm buildings (fixed assets).
• It is used to purchase inputs such as seeds, fertilizers, feeds and agro-chemicals.
• It is used to pay wages to hired labour and to hire services.
• It provides working funds for storage, processing, transport and marketing of produce.

(c) Five major roles of middlemen in marketing agricultural produce [5 marks]

• Assembling/buying: they gather (bulk) produce from many scattered small farmers into large quantities.
• Transportation: they move the produce from the farms/production areas to the markets and consumers.
• Storage: they store produce and make it available throughout the year, evening out seasonal supply.
• Processing and grading: they process, grade, package and preserve the produce to add value and meet consumer needs.
• Financing and risk-bearing: they provide finance (sometimes advance money/credit to farmers) and bear the risks of price change, spoilage and loss; they also distribute the produce and pass market information to farmers.

Détails de la réponse

(a) Construction of a fish pond

A good site with a gentle slope, near a reliable source of clean water and on soil that holds water (clayey/loamy) is selected. The area is cleared of bush, stumps and debris and the outline of the pond is marked out. The topsoil is removed and the pond is dug to the required depth (deeper at one end so that it can be drained). An embankment (dyke) is built round the pond and compacted so that it is firm and does not leak. A water inlet (pipe or channel) is provided to let water in and an outlet/monk with a screen is provided to control the water level and to drain the pond; the screens keep fish in and predators out. The pond bottom and dykes are made watertight (a clay lining or concrete may be used), the pond is limed and manured to encourage the growth of natural fish food, then it is filled with water and stocked with fingerlings.

(b) Eight measures for efficient operation of an egg incubator

• Select and set only fertile, clean, medium-sized and well-shaped eggs.
• Maintain the correct incubation temperature (about 37.5 to 39°C / 100°F).
• Maintain the correct humidity in the incubator to prevent the eggs from drying up.
• Turn the eggs regularly (several times a day) to prevent the embryo from sticking to the shell.
• Provide adequate ventilation so that fresh air (oxygen) reaches the eggs and carbon dioxide is removed.
• Candle the eggs to detect and remove infertile or dead-in-shell eggs.
• Keep the incubator clean and disinfected to prevent disease.
• Ensure a steady, uninterrupted source of power/heat and check the thermostat and thermometer regularly for accuracy.

Détails de la réponse

(a) Budding and grafting [4 marks]

• Budding is a method of vegetative (asexual) propagation in which a single bud, cut with a piece of bark from a desired parent plant (the scion), is inserted into a slit in the bark of a rootstock so that the two unite and grow as one plant.
• Grafting is a method of vegetative propagation in which a portion of stem bearing several buds (the scion) from a desired plant is joined onto the rootstock of another plant so that their cambium layers unite and continue to grow together.

(b) Four materials required for budding [4 marks]

• A sharp budding knife.
• A healthy rootstock.
• Bud sticks (scion bearing buds) from the desired parent plant.
• Budding tape/raffia (or polythene strip) for wrapping the union, and wax to seal it.

(c) Two reasons why improvement of crops by selection may not give desired results [4 marks]

• The desirable character selected may be controlled by recessive genes, so it fails to show up in the offspring.
• Cross-pollination (out-crossing) with inferior plants nearby, and the influence of environment rather than genes, can mask or lose the selected trait in later generations.

(d) Four disadvantages of asexual and four advantages of sexual reproduction [8 marks]

Disadvantages of asexual reproduction:

• There is no genetic variation, so no improved varieties arise.
• Diseases present in the parent are passed on to the offspring.
• The offspring are all weak in the same way and can be wiped out by the same disease/pest.
• It does not allow the crop to adapt to new/changing environments.

Advantages of sexual reproduction:

• It produces variation, which is the basis for crop improvement and new varieties.
• The seeds produced are easy to store, handle and transport.
• Offspring may be more vigorous (hybrid vigour) and better adapted to the environment.
• It gives a means of surviving unfavourable conditions through resistant/dormant seeds and reduces carry-over of some diseases.

Détails de la réponse

(a) Effects of rural-urban migration on agricultural production

Rural-urban migration is the movement of people, especially the young and able-bodied, from the villages to the towns. Its effects on agriculture are largely negative: it causes a shortage of farm labour in the rural areas so that farms are under-cultivated; it leaves farming in the hands of the old, women and children who cannot work large farms; it lowers total food and cash-crop production and can cause food scarcity and higher food prices; it leads to abandonment of farmland and reduced use of improved practices; and it raises the cost of the few available labourers. A minor positive effect is that the migrants may send money (remittances) home to invest in farming, and reduced pressure on land can, in some cases, allow mechanisation.

(b) Effect of demand and supply on production

• (i) Demand (supply constant): When the demand for a produce rises while supply stays constant, its price rises; the higher price encourages farmers to produce more of that commodity. If demand falls, price falls and farmers reduce production.
• (ii) Supply (demand constant): When supply increases while demand stays constant, price falls, which discourages farmers and they cut back production; when supply is scarce, price rises and farmers are encouraged to produce more.

(c) Effects on farmers' income

• (i) Demand on income (price constant): a rise in demand means more produce is sold, so total income rises; a fall in demand means less is sold, so income falls.
• (ii) Supply on income (demand constant): a large supply (glut) forces prices down, which can reduce total income; a moderate/short supply raises price and can increase income per unit sold.

(d) Five roles expected of a farm manager [5 marks]

• Planning and organising the farm's activities and resources.
• Directing and supervising the farm workers.
• Keeping proper farm records and accounts.
• Making decisions on what, how and when to produce and market.
• Sourcing inputs and finance, and controlling/evaluating the farm to ensure it makes a profit.

Détails de la réponse

(a) Definition of land [2 marks]

Land is the solid part of the earth's surface, together with all the natural resources on, above and beneath it (soil, water, minerals, air and vegetation), that man uses for agricultural and other purposes. In economics it is a free gift of nature and a factor of production.

(b) Two major classifications of land based on uses, with two examples each [4 marks]

• Agricultural land use: land used for growing crops (arable farming) and for grazing/rearing livestock. Examples: cultivating maize/yam; keeping cattle on rangeland.
• Non-agricultural land use: land used for purposes other than farming. Examples: building of houses/roads (construction) and mining/industrial or recreational use.

(c) Six factors that influence availability of land for agricultural production, explaining two [6 marks]

Six factors: (1) land tenure system, (2) population pressure/urbanisation, (3) topography and soil condition, (4) climate/rainfall, (5) government policy, (6) presence of pests and diseases (e.g. tsetse fly).

Explanation of two:

• Land tenure system: Where land is communally or fragmentally owned, a farmer cannot easily acquire a large continuous piece of land, and insecurity of tenure discourages permanent investment; this reduces the land available for serious farming.
• Population pressure and urbanisation: As population grows and towns expand, land is taken up for housing, roads, schools and industry, so less land is left for agriculture, and remaining farmland becomes overused.

Détails de la réponse

(a) Three methods of irrigating a small nursery [3 marks]

• Watering with a watering can (hand watering).
• Sprinkler (overhead spray) irrigation.
• Drip (trickle) irrigation, or the use of a hose.

(b) Three factors considered in the choice of each method [6 marks]

(i) Surface irrigation:

• The topography of the land (it must be fairly level/gentle slope).
• The type/texture of the soil and its infiltration rate.
• The quantity of water available and the type of crop grown.

(ii) Sub-surface irrigation:

• The depth and nature of the water table.
• The soil type and its capacity to move water upward (capillarity/permeability).
• The cost of installation and the quality of the water (it must be free of salts to avoid salinity).

(c) Two advantages of sub-surface irrigation [2 marks]

• It supplies water directly to the roots with little loss through evaporation, so water is conserved.
• The soil surface stays dry, which reduces weed growth and the spread of foliar (leaf) diseases.

(d) Five ways of reducing build-up of diseases on an irrigated farm [5 marks]

• Practise crop rotation to break the life cycle of pathogens.
• Use clean, disease-free (treated) planting materials and resistant varieties.
• Ensure good drainage so that the land is not waterlogged.
• Keep the farm clean by removing and destroying infected plants and weeds (field sanitation).
• Use clean irrigation water and apply appropriate chemicals/biological control against pests and diseases.