WAEC SSCE - Agricultural Science - 2006 (Essay)

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(a) Life cycle of the liver-fluke (Fasciola hepatica): An annotated diagram should be drawn as a cycle with arrows linking the stages below. The liver-fluke needs two hosts: the primary host (sheep, cattle, goat) and the intermediate host (a mud/water snail).

• Adult flukes live in the bile ducts/liver of the primary host and lay eggs.
• Eggs pass out with the faeces of the animal onto wet pasture.
• In water, each egg hatches into a ciliated larva called a miracidium.
• The miracidium enters a mud snail (intermediate host) and develops through the sporocyst and redia stages, multiplying.
• These develop into tadpole-like cercariae which leave the snail.
• The cercariae encyst on wet grass as metacercariae (the infective stage).
• A grazing animal swallows the metacercariae, which travel to the liver, grow into adult flukes, and the cycle repeats.

Preventing the fluke from completing its life cycle in the field:

• Drain marshy/water-logged grazing land to destroy the snail habitat.
• Kill the mud snails using molluscicides (for example copper sulphate).
• Avoid grazing animals on wet, low-lying pastures, especially in the early morning.
• Deworm (drench) infected animals regularly and dispose of their dung properly to break the cycle.

(c) Three effects of lice on animal production:

• They suck blood and cause anaemia and loss of condition.
• Their bites cause irritation and restlessness, reducing feeding and growth.
• They damage the skin/hide and transmit diseases, lowering the value of the animal.

Détails de la réponse

(a) Annotated diagram of the water cycle

(b) Importance of water to crops

1. Water is a raw material used in photosynthesis.
2. It dissolves mineral salts in the soil, making them available for absorption by roots.
3. It serves as a medium for the translocation of mineral nutrients and manufactured food in the plant.
4. It maintains the turgidity of cells, thereby keeping leaves and stems firm.
5. It is required for seed germination.
6. It cools the plant during transpiration.

(c) Ways of conserving water in the soil

1. Mulching the soil surface to reduce evaporation.
2. Adding humus or organic manure to improve the water-holding capacity of the soil.
3. Growing cover crops to shade the soil and reduce evaporation and run-off.
4. Practising contour ridging or terracing to reduce surface run-off and increase infiltration.

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(a) Four target groups of the extension agent:

• Crop farmers
• Livestock (animal) farmers
• Rural women/farmers' wives
• Youths and school leavers
• Farmers' cooperatives and organisations

(b) Five important qualities of a good extension worker:

• Good knowledge of agriculture: he must be well trained and understand modern farming practices so as to teach farmers correctly.
• Good communication skill: he must be able to pass information clearly in the local language the farmers understand.
• Patience and tolerance: he must be patient with farmers who learn slowly or resist new ideas.
• Honesty and good character: he must be trustworthy so that farmers will believe and accept his advice.
• Ability to relate well with people (good human relations): he must be friendly, approachable and able to win the confidence of the farmers.

(c) Four functions of an extension worker:

• To teach farmers improved and modern farming methods.
• To carry farmers' problems to research stations and bring research findings back to farmers.
• To organise demonstrations, field days, shows and training for farmers.
• To help farmers form and run cooperative societies and obtain inputs and credit.

Détails de la réponse

(a) Three characteristics of agricultural non-governmental organizations (NGOs):

• They are non-profit making; they are not established to earn profit for owners.
• They are voluntary and privately owned, that is, they are not owned or run by government.
• They are usually funded through donations, grants, membership dues and international aid.
• They operate in specific areas of agriculture such as research, funding, or extension.

(b)(i) Five objectives of the West Africa Rice Development Agency (WARDA / AfricaRice):

• To carry out research aimed at increasing rice production in West Africa.
• To develop improved, high-yielding rice varieties (for example NERICA).
• To train rice farmers and national research staff in modern rice production techniques.
• To reduce the region's dependence on imported rice and improve food security.
• To collect, store and distribute improved rice seeds and information to member countries.

(b)(ii) Five objectives of the International Institute of Tropical Agriculture (IITA):

• To conduct research to increase the production of tropical food crops such as yam, cassava, cowpea, maize and soybean.
• To develop improved and disease-resistant crop varieties.
• To develop sustainable farming systems that conserve soil and the environment.
• To train agricultural scientists, technicians and farmers.
• To maintain a gene bank and conserve the genetic resources of tropical crops.

(c) Three other non-governmental organizations involved in agricultural development:

• Food and Agriculture Organization (FAO).
• Sasakawa Global 2000.
• International Fund for Agricultural Development (IFAD).

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(a) Definition of farmstead: A farmstead is the part of the farm on which the farm buildings and structures (such as the farmhouse, barns, stores, animal houses, processing sheds and roads) are sited and arranged for the efficient running of the farm.

(b) Four factors to be considered in planning a farmstead:

• Topography (nature/slope of the land)
• Source of water supply
• Nature and type of soil
• Accessibility and nearness to roads/market

(c) Importance of the factors listed above:

(d) Two reasons for planning a farmstead:

• To make efficient use of the available land and avoid waste of space.
• To reduce the cost of labour and movement and so improve the efficiency of farm operations.

Détails de la réponse

(a) Definition of an insecticide: An insecticide is a chemical substance (a type of pesticide) used to kill or control insect pests on crops, animals or stored produce.

(b) Four groups of insecticides:

• Contact insecticides
• Systemic insecticides
• Stomach-poison (ingested) insecticides
• Fumigants

(c) Class of pesticide used for each pest:

(d) Two effects of each pest-control measure on the environment:

(i) Chemical control:

• It pollutes the soil, water and air with toxic residues.
• It kills useful, non-target organisms such as bees, natural enemies and soil organisms, and residues can harm human health.

(ii) Cultural control:

• It is environmentally friendly and leaves no toxic residues.
• Practices such as bush burning, however, can destroy soil organisms and expose the soil to erosion.

(iii) Biological control:

• It maintains ecological balance and does not pollute the environment.
• An introduced predator or parasite may become a pest itself and upset the natural balance if not well controlled.

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(a) Four ways by which diseases are spread on a crop farm:

• Through infected planting materials (seeds, cuttings, suckers).
• By wind, which carries fungal spores and bacteria.
• By water (rain splash and irrigation water) that washes pathogens from plant to plant.
• By insect vectors and other animals that carry pathogens.
• Through contaminated farm tools, implements and the hands/clothing of workers.

(b)(i) Onion twister:

Three symptoms:

• Twisting and curling of the leaves.
• Yellowing and dieback of the leaves.
• Stunted growth and rotting/reduction of the bulbs.

Three control measures:

• Plant clean, disease-free seeds/setts and resistant varieties.
• Practise crop rotation and field sanitation (remove and burn infected plants).
• Apply appropriate fungicides.

(b)(ii) Root-knot of tomato (root-knot nematode):

Three symptoms:

• Swellings, galls or knots on the roots.
• Stunted growth of the plant.
• Yellowing of leaves and wilting during hot periods.

Three control measures:

• Practise crop rotation with non-host crops.
• Use resistant varieties and clean, nematode-free seedlings.
• Apply nematicides and/or solarise or flood the soil before planting.

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(a) Candling in chick production: Candling is the process of passing a bright light through an egg in a dark room to examine its interior. It is used to check whether an egg is fertile, to follow the development of the embryo during incubation, and to detect and remove infertile or dead (addled) eggs.

(b) Intensive method of managing poultry:

(i) Sanitation:

• The house, feeders and drinkers should be cleaned and disinfected regularly.
• Litter should be kept clean and dry, and wet or caked litter removed to prevent disease.
• Dead birds should be removed and properly disposed of, and a foot-dip/disinfectant used at the entrance to control disease spread.

(ii) Feeding:

• Birds are fed balanced rations appropriate to their age (chick mash, growers' mash, layers' mash or broiler finisher).
• Clean, cool water must be provided at all times, and feed given in the right quantity to avoid waste.
• Feeders and drinkers should be well spaced so that all birds have easy access.

(c) Six breeds of pigs:

• Large White (Yorkshire)
• Landrace
• Duroc
• Hampshire
• Berkshire
• Tamworth

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(a) Four asexual methods of crop propagation:

• Propagation by cuttings (for example cassava, sugar-cane)
• Propagation by budding
• Propagation by grafting
• Propagation by layering
• Propagation by suckers, tubers, bulbs or corms

(b) Definitions:

• (i) Mixed farming: The practice of growing crops and rearing animals together on the same piece of land at the same time, where each enterprise supports the other.
• (ii) Inter-cropping: The practice of growing two or more different crops together on the same piece of land at the same time.
• (iii) Ley farming: A system in which land is put under arable (crop) cultivation for some years and then put under grass or pasture for grazing for a period before returning it to crops, in rotation.

(c) Four advantages of mixed farming:

• Animal dung is used as manure to improve soil fertility for the crops.
• Crop residues and by-products are used to feed the animals.
• It provides a steady, all-year-round income from both crops and animals.
• It spreads the risk of total farm failure and makes fuller use of land and labour.

Four advantages of inter-cropping:

• It gives a higher total yield and better use of the land per unit area.
• Leguminous crops in the mixture add nitrogen to the soil for the other crops.
• The ground cover reduces soil erosion and suppresses weeds.
• It insures the farmer against total loss if one crop fails.

Détails de la réponse

(a) Five reasons why farm accounts are kept:

• To find out whether the farm is making a profit or a loss.
• To help the farmer plan and budget for the future.
• To serve as a basis for obtaining loans/credit from banks and other lenders.
• To help in assessing tax payable and settling disputes.
• To compare the performance of the farm from one year to another and between enterprises.

(b) Profit and Loss Account for UNITY FARM for the year ending December 2005:

Produce consumed on the farm and given out as gifts are treated as farm income (benefits in kind).

Working:

\[ \text{Total income} = 29{,}000 + 7{,}000 + 5{,}500 + 300 + 1{,}000 = D42{,}800.00 \]

\[ \text{Total expenditure} = 1{,}400 + 1{,}200 + 1{,}900 + 2{,}000 + 1{,}100 + 1{,}200 + 1{,}500 + 6{,}000 + 4{,}400 = D20{,}700.00 \]

\[ \text{Net profit} = 42{,}800 - 20{,}700 = D22{,}100.00 \]