WAEC SSCE - Agricultural Science - 2012 (Essay)

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(a) Law of diminishing returns

The law of diminishing returns states that when successive units of a variable factor are added to fixed factors of production, total output will initially increase, but after a certain point each additional unit of the variable factor adds less to total output than the preceding unit.

(b)(i) Input-output graph

Using the scale shown by the axes, plot the following points and join them with a smooth curve:

Fertilizer input (bags)	Sorghum yield (kg)
0	8
6	30
12	50
18	90
24	140
28	170
32	190
36	200
40	200
46	190

(b)(ii) Relationship between fertilizer input and sorghum yield

1. As fertilizer application increases from 0 to 36 bags, sorghum yield increases from 8 kg to 200 kg.
2. After about 24 bags, additional fertilizer gives progressively smaller increases in yield: 30 kg from 24 to 28 bags, 20 kg from 28 to 32 bags, and 10 kg from 32 to 36 bags. This is the stage of diminishing returns.
3. At 36 to 40 bags, the maximum yield of 200 kg is reached. Further application to 46 bags reduces yield to 190 kg, showing negative returns.

(c) Functions of an agricultural extension agent

1. Teaches and demonstrates improved farming methods and innovations to farmers.
2. Serves as a link between farmers, government and agricultural research institutions.
3. Disseminates agricultural information and advises farmers on farm management problems.
4. Assists farmers to obtain farm inputs, credit facilities and marketing information.

(d) Benefits of commodity boards in the marketing of agricultural produce in West Africa

1. They provide a ready market for agricultural commodities.
2. They announce guaranteed prices and help to stabilize farmers' incomes.
3. They carry out grading, standardization and quality control of produce.
4. They provide storage, processing, transportation and other marketing services.
5. They assist farmers with credit, subsidies, farm inputs and technical advice.

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(a) Loan and subsidy

• Loan: a repayable credit, in cash or kind, granted to a farmer for agricultural purposes. It may attract interest.
• Subsidy: non-repayable financial assistance, usually provided by government, to reduce part of the cost of farm inputs or services.

(b)(i) Supply

Supply is the quantity of a commodity which producers are willing and able to offer for sale at various prices over a given period of time.

(b)(ii) Supply curve for cocoa

Supply of cocoa (tonnes)	Price of cocoa (Le)
450	10,000
550	15,000
700	20,000
1,000	25,000
1,700	30,000

Plot the points (450, 10,000), (550, 15,000), (700, 20,000), (1,000, 25,000) and (1,700, 30,000), with supply on the horizontal axis and price on the vertical axis. Join the points to obtain the supply curve.

(b)(iii) Relationship between price and supply

The supply curve slopes upwards from left to right. This shows a direct relationship between price and quantity supplied: as the price of cocoa rises from Le10,000 to Le30,000, quantity supplied rises from 450 tonnes to 1,700 tonnes. Conversely, a lower price leads to a lower quantity supplied.

(c) Farm and home visits in agricultural extension

Advantages

1. The extension worker obtains first-hand knowledge of the farmer's farm and the actual problems faced.
2. It promotes personal contact, goodwill, confidence and mutual trust between the farmer and the extension worker.

Disadvantages

1. It is expensive and time-consuming, especially where farms are widely scattered.
2. Only a few farmers can be reached at a time.

(d) Characteristics of agricultural produce in marketing

1. Perishability: many agricultural products spoil rapidly after harvest.
2. Seasonality: production is seasonal, causing fluctuations in supply and price.
3. Bulkiness: many products are bulky and costly to transport and store.

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(a)(i) Malnutrition in animal production [2 marks]

Malnutrition is a condition in which an animal is poorly nourished because its diet is unbalanced, that is, it lacks or has too little (or an excess) of one or more essential nutrients such as proteins, minerals, vitamins or energy.

(a)(ii) Four effects of malnutrition on farm animals [4 marks]

• Stunted (retarded) growth and loss of body weight.
• Low productivity, that is, poor milk, egg or meat yield.
• Reduced fertility and poor reproductive performance.
• Lowered resistance to diseases, leading to easy infection and sometimes death.

(b) Methods of rangeland improvement [6 marks]

• (i) Rotational grazing: The range is divided into paddocks and the animals are moved from one paddock to another in turn, so that grazed portions are rested and allowed to regrow; this prevents overgrazing and gives even utilisation of the pasture.
• (ii) Reseeding: Improved and more nutritious grass and legume seeds are sown to replace poor or worn-out species, thereby raising the quality and quantity of forage on the range.
• (iii) Controlled stocking: The number of animals kept on the land is matched to its carrying capacity so that the pasture is neither overgrazed nor undergrazed, keeping the range productive.

(c) Four objectives of animal improvement programmes in West Africa [4 marks]

• To develop breeds that grow faster and give higher meat, milk or egg yield.
• To breed animals that are resistant to diseases and parasites.
• To produce animals well adapted to the tropical (hot) climate and local feeds.
• To improve fertility/prolificacy and the overall quality of the national herd.

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(a) Subsistence agriculture [2 marks]

Subsistence agriculture is a type of farming in which the farmer produces crops and livestock mainly to feed himself and his family, with little or nothing left over for sale.

(b) Interdependence of agriculture and industry [6 marks]

• (i) Tools, implements and machinery industries: Agriculture depends on these industries for the supply of cutlasses, hoes, ploughs, harrows and tractors used in farm operations, while the industries in turn depend on agriculture as a market for their products and for raw materials such as metals and rubber; a strong farming demand keeps such factories in business.
• (ii) Processing industries: Agriculture supplies the raw materials (cocoa, oil palm, cotton, cassava, grains) that processing industries convert into finished goods, while the processing industries provide farmers with a ready market and add value to farm produce, thereby raising farmers' income.
• (iii) Agro-chemical industries: These supply farmers with fertilizers, herbicides, insecticides and drugs that raise crop yield and protect livestock, while agriculture provides the demand that sustains the chemical industries and, in some cases, the plant raw materials they use.

(c)(i) Farm surveying [2 marks]

Farm surveying is the measurement of a piece of farmland to determine its size (area), shape, boundaries and the relative positions of features on it, and to represent them on a plan or map.

(c)(ii) The 3, 4, 5 method [6 marks]

The 3, 4, 5 method is used to set out or check a right angle (90°) at a corner of a farm. It is based on Pythagoras' theorem: a triangle whose sides are in the ratio 3 : 4 : 5 must contain a right angle between the sides 3 and 4, because

\[3^2 + 4^2 = 9 + 16 = 25 = 5^2.\]

To use it: from the corner peg (O), a distance of 3 units (e.g. 3 m) is measured along one line and a peg fixed (A); from the same corner, 4 units are measured along the second line and a peg fixed (B); the distance between A and B (the hypotenuse) is then adjusted until it is exactly 5 units. When AB = 5, the angle at O is a perfect right angle. See diagram.

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(a) Communal land tenure system [2 marks]

Communal land tenure is a system of land ownership in which land belongs to the whole community (village or family) as a group, and individual members are only given the right to use portions of it, but no single member owns the land outright.

(b) Two objectives of each development programme [6 marks]

• (i) Farm settlement schemes: to settle and employ young school-leavers and unemployed people in modern farming; and to increase agricultural production and demonstrate improved farming methods.
• (ii) River basin authorities: to provide water for irrigation so that farming can go on all year round; and to control flooding and provide water for domestic, fishing and hydro-electric use.
• (iii) Agricultural development projects (ADPs): to provide extension services and improved inputs to farmers; and to construct rural infrastructure (feeder roads, dams, markets) that boosts food production.

(c)(i) Farm machinery versus farm implements [2 marks]

Farm machinery are engine-powered (self-propelled or motorised) equipment that generate their own power to do farm work, whereas farm implements are the simpler, non-powered tools/attachments that either do work by hand or are coupled to and drawn by a source of power such as a tractor.

(c)(ii) Six examples of each [6 marks]

Farm machinery: tractor, combine harvester, power tiller, milking machine, water pump, sheller/thresher.

Farm implements: plough, harrow, ridger, planter, cutlass, hoe.

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(a) Four factors that affect the type of soil formed at a place [2 marks]

• Nature of the parent rock (parent material).
• Climate (rainfall and temperature).
• Living organisms (vegetation and soil organisms).
• Topography (relief) and length of time of soil formation.

(b) Uses of land [4 marks]

• (i) Two agricultural uses: for growing crops (crop cultivation) and for rearing/grazing livestock.
• (ii) Two non-agricultural uses: for building houses and roads (construction) and for mining/industrial and recreational purposes.

(c) Functions and deficiency symptoms of the nutrients [8 marks]

(d) Two ways soil structure is important in agriculture [2 marks]

• It determines soil aeration and drainage, which affect root respiration and water movement.
• It influences root penetration, water-holding capacity and the ease of tillage of the soil.

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(a) Four characteristics of a fertile soil [4 marks]

• It is rich in plant nutrients (nitrogen, phosphorus, potassium, etc.).
• It has good structure and texture that allow proper aeration and root penetration.
• It has a good water-holding capacity while still draining well.
• It has a favourable (near-neutral) pH and a good population of soil living organisms plus adequate organic matter (humus).

(b) Three factors that affect land availability for agricultural production in West Africa [6 marks]

• Land tenure system: Communal and fragmented ownership makes it difficult for a farmer to acquire and hold large continuous pieces of land for farming.
• Population pressure and urbanisation: Growing population and the expansion of towns, roads and industries take away farmland for building and other non-farm uses, reducing the land available for agriculture.
• Nature/topography and soil condition: Rocky, mountainous, waterlogged, eroded or desert (arid) land is unsuitable for cultivation, so such areas reduce the amount of usable farmland.

(c) Four benefits of draining farm lands [4 marks]

• It removes excess water and prevents waterlogging of the soil.
• It improves soil aeration, which favours root respiration and the activity of soil organisms.
• It raises soil temperature and allows the land to be worked and planted early.
• It reduces the incidence of water-borne pests, diseases and root rot, and reduces leaching of nutrients.

(d) Two sources of soil nitrogen [2 marks]

• Fixation of atmospheric nitrogen by leguminous plants (Rhizobium bacteria) and lightning.
• Decay of organic matter (plant residues, animal dung) and application of nitrogenous fertilizers.

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(a)(i) Natural pasture [2 marks]

Natural pasture is grassland made up of grasses, legumes and other herbs that grow on their own (naturally) without being deliberately planted or managed by man, and on which animals graze.

(a)(ii) Four characteristics of natural pastures in West Africa [4 marks]

• They are made up mainly of grasses with few legumes.
• They are dominated by tall, coarse grasses of low nutritive (feeding) value.
• They grow luxuriantly in the rainy season but dry up and become poor in the dry season.
• They contain a mixture of many different (unimproved) species and are often subject to bush burning.

(b) Root-knot disease of tomato [6 marks]

• (i) Causal organism: a nematode (eelworm), Meloidogyne species.
• (ii) Mode of transmission: spread through infested soil, and through movement of infected seedlings, farm tools, irrigation/run-off water and soil carried on implements or feet.
• (iii) Two symptoms: formation of knots, galls or swellings on the roots; stunted growth with yellowing and wilting of the plant (poor yield).
• (iv) Two control measures: practise crop rotation and use resistant varieties; treat/sterilise the soil with nematicides and destroy (uproot and burn) infected plants.

(c) Grafting versus budding [2 marks]

In grafting, a portion of stem (scion) bearing several buds is joined onto the rootstock, whereas in budding only a single bud is inserted into the bark of the rootstock.

(d) Two uses of sugarcane [2 marks]

• It is used for the production of sugar and syrup.
• It is chewed as food and used in making alcohol/ethanol and animal feed (by-products such as molasses).

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(a)(i) Incubation in poultry production [2 marks]

Incubation is the process of applying the correct warmth (heat), humidity and turning to fertile eggs for the period (about 21 days in the fowl) needed for the embryo to develop and hatch into a chick.

(a)(ii) Natural incubation: two advantages and two disadvantages [4 marks]

Advantages:

• It is cheap and needs no equipment or electricity.
• The mother hen provides warmth, turning and brooding, and cares for the chicks after hatching.

Disadvantages:

• Only a few eggs can be hatched at a time (limited number).
• The hen stops laying while brooding, and hatching cannot be planned/controlled; diseases and parasites may also be passed to the chicks.

(b) Four factors that affect pasture establishment in West Africa [4 marks]

• Rainfall/moisture availability.
• Soil type and fertility.
• Type/quality of seed and species of forage used.
• Method of land preparation and control of weeds, pests and bush fires (and grazing pressure).

(c) Causal organisms and symptoms of the diseases [6 marks]

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(a) Forest reserve [2 marks]

A forest reserve is an area of forest land set aside and protected by law, mainly for the conservation and controlled production of forest resources, especially valuable tree species.

(b) Advantages of the taungya system of farming [4 marks]

(i) To farmers:

1. They obtain fertile land on which to grow food crops, often at little or no cost.
2. They obtain food, income and employment while the forest trees are still young.

(ii) To foresters:

1. Farmers weed and tend the young forest trees while cultivating their crops.
2. The cost of establishing and maintaining the forest plantation is reduced.

(c) Life cycle of yam beetle, Heteroligus metes [6 marks]

The yam beetle undergoes complete metamorphosis, as shown below.

1. The adult female beetle lays eggs in moist soil, usually under mulch, at the beginning of the yam-growing season.
2. The eggs hatch into larvae or grubs. The grubs feed mainly on decaying organic matter in the soil.
3. The larva moults through three larval stages and later changes into a pupa in the soil.
4. The pupa develops and moults into an adult beetle.
5. The adult beetle attacks yam tubers by boring into them and feeding on the tuber tissue. The female subsequently lays eggs and the cycle continues.

(d) Advantages of organic fertilizers over inorganic fertilizers [2 marks]

1. They add humus and improve soil structure and water-holding capacity.
2. They release nutrients gradually and are less likely to make the soil acidic.

(e) Varieties of oil palm [2 marks]

1. Dura
2. Tenera