WAEC SSCE - Agricultural Science - 2002 (Essay)

Detalles de la respuesta

(a) Four methods of weed dispersal

• Wind dispersal: light seeds with hairs or wings (e.g. Tridax, Spear grass) are blown by wind.
• Water dispersal: seeds are carried by run-off water and streams to new sites.
• Animal dispersal: seeds with hooks or spines stick to animal fur, or are eaten and passed out in droppings.
• Self/explosive dispersal: the fruit bursts open on drying and flings the seeds away (e.g. Centrosema).
• (Man/agents also disperse weed seeds through contaminated crop seed, farm implements and manure.)

(b) Three mechanical methods of weed control

• Hand pulling / hoeing of weeds.
• Slashing or cutting with a cutlass.
• Mowing, tillage or ploughing to uproot and bury weeds.

Three cultural methods of weed control

• Mulching the soil surface to smother weeds.
• Crop rotation to break the weed life-cycle.
• Use of close/proper spacing and cover crops to shade out weeds.
• (Flooding of fields and timely land preparation are also acceptable.)

Detalles de la respuesta

(a)(i) Five effects of irrigation on crop production

• It supplies water to crops during the dry season, allowing all-year-round cultivation.
• It increases crop yield by ensuring adequate moisture for growth.
• It dissolves soil nutrients and makes them available to plant roots.
• It aids seed germination and establishment of seedlings.
• It reduces the risk of crop failure caused by drought.
• (Negative) Excess or poor irrigation can cause waterlogging, leaching of nutrients and salinity/salt build-up.

(a)(ii) Five effects of drainage on crop production

• It removes excess water from the soil and prevents waterlogging.
• It improves soil aeration, giving roots enough oxygen for respiration.
• It warms the soil, promoting seed germination and root growth.
• It improves soil structure and workability for cultivation.
• It reduces the incidence of soil-borne diseases associated with wet soils.
• (Negative) Over-drainage can dry out the soil and remove needed moisture and nutrients.

(b) Four methods of surface irrigation

1. Basin/flooding irrigation.
2. Furrow irrigation.
3. Border (border-strip) irrigation.
4. Wild flooding / check-basin irrigation.

(c) Two main reasons why surface drainage is often necessary

• To remove excess rain or flood water from the surface and prevent waterlogging of crops.
• To improve soil aeration and workability so that crop roots and farm operations are not hindered.

Detalles de la respuesta

(a) Six types of land tenure systems

1. Communal land tenure (land owned by the community/village).
2. Inheritance land tenure (land passed down within the family).
3. Freehold land tenure (outright individual ownership by purchase).
4. Leasehold land tenure (land held for a fixed period by agreement).
5. Rent/tenant land tenure (land held by paying rent to the owner).
6. Gift land tenure (land acquired as a gift).

(Others acceptable: pledge tenure, tenant-at-will, government/state land acquisition.)

(b) Five reasons why the government should enforce land use legislation

• To ensure orderly and planned use of land, preventing indiscriminate development.
• To make land readily available and accessible for large-scale agricultural production.
• To reduce or settle disputes and litigation over land ownership.
• To make it easier for farmers to obtain land as collateral to secure agricultural loans.
• To prevent fragmentation of land into uneconomically small holdings.
• To promote conservation and prevent misuse or degradation of land resources.
• To ensure fair distribution of land and check land speculation by a few individuals.

Detalles de la respuesta

(a)(i) Five objectives of the Farm Settlement Scheme

• To reduce rural-urban migration by making farming attractive and rewarding to young school leavers.
• To modernise agriculture through the use of improved inputs, mechanisation and better farming techniques.
• To provide gainful employment for youths and reduce unemployment.
• To increase the production of food and industrial raw materials.
• To serve as demonstration centres where surrounding farmers can learn improved practices.

(a)(ii) Five objectives of the Agricultural Development Programme (ADP)

• To increase food production and raise the income of small-scale farmers.
• To provide rural infrastructure such as feeder roads, boreholes and storage facilities.
• To make improved inputs (fertilizer, improved seeds, agro-chemicals) available to farmers at the right time.
• To provide effective extension services and technical advice to farmers.
• To carry out adaptive research suited to the local farming conditions.

(b) Roles of cooperative organisations in agricultural production

• They provide credit and loans to member farmers at low interest rates.
• They buy farm inputs in bulk and supply them to members at cheaper prices.
• They market members produce collectively, thereby securing better prices.
• They provide storage and processing facilities for members produce.
• They educate members on improved farming methods.
• They provide farm machinery and equipment for members to hire.

Detalles de la respuesta

(a) Three functions of nitrogen in crop plants

• It is a major component of proteins, enzymes and protoplasm needed for growth.
• It is a constituent of chlorophyll, giving leaves their green colour for photosynthesis.
• It promotes vegetative growth, producing healthy leaves and stems.

(b) Four effects of excess soil nitrogen

• Excessive vegetative (leafy) growth at the expense of flowering and fruiting.
• Delayed maturity of the crop.
• Weak, succulent stems that lodge (fall over) easily.
• Increased susceptibility to pests and diseases; scorching of plants at very high levels.

Three effects of nitrogen deficiency

• Yellowing of leaves (chlorosis), beginning with the older leaves.
• Stunted growth and small leaves.
• Reduced yield and premature shedding of leaves.

(c) Three other ways (apart from lightning) by which nitrogen is added to the soil

• Fixation of atmospheric nitrogen by nitrogen-fixing bacteria (e.g. Rhizobium in legume root nodules).
• Application of nitrogenous fertilizers (e.g. urea, sulphate of ammonia).
• Addition of organic manure and decayed plant and animal remains.

(d) Six soil micronutrients

1. Iron (Fe)
2. Manganese (Mn)
3. Zinc (Zn)
4. Copper (Cu)
5. Boron (B)
6. Molybdenum (Mo)

(Chlorine, Cl, is also acceptable.)

Detalles de la respuesta

(a)(i) What is culling?

Culling is the removal or elimination of unproductive, sick, weak, old or undesirable animals from a herd or flock so that only healthy and productive animals are kept.

(a)(ii) Three reasons why culling is practised

• To remove unproductive and uneconomical animals and reduce cost of feeding.
• To eliminate sick, weak and diseased animals and check the spread of disease.
• To improve the quality of the herd/flock through selection of the best breeding stock.

(b)(i) Deep litter system

Advantages

• Birds move about freely and exercise, giving good health.
• Lower cost of construction and equipment.
• Litter can be used as manure and birds can obtain some vitamin B from it.

Disadvantages

• Diseases and parasites spread easily among birds in contact with litter.
• Difficult to detect and cull sick or non-laying birds individually.
• Damp litter causes ammonia build-up and disease; eggs may be dirty or eaten.

(b)(ii) Battery cage system

Advantages

• Easy identification and culling of individual sick or non-laying birds.
• Reduced spread of diseases and parasites since birds do not touch droppings.
• Clean eggs are obtained and egg laying is easily recorded.

Disadvantages

• High cost of purchasing and installing the cages.
• Birds lack exercise and may develop weak bones or cage fatigue.
• Requires skilled labour and steady management; vices such as feather pecking may occur.

Detalles de la respuesta

(a) Fungal disease, viral disease and pest of four crops

(Candidate needs any four crops only.)

(b) Six general control measures of crop diseases

• Plant disease-resistant/tolerant varieties.
• Use certified, disease-free seeds and planting materials.
• Practise crop rotation to break the disease cycle.
• Practise good field sanitation by removing and burning infected plants.
• Apply appropriate chemicals such as fungicides.
• Control insect vectors that spread diseases.
• (Also: proper spacing to reduce humidity, and early planting.)

Detalles de la respuesta

(a) Definition of disease

A disease is any departure from the normal state of health of an animal in which the body or some of its parts fail to function properly, usually caused by a pathogen, deficiency or disorder.

(b) Difference between resistance and susceptibility

Resistance is the natural ability of an animal to withstand or overcome infection by a disease-causing organism without becoming ill, whereas susceptibility is the inability of an animal to withstand infection, so that it easily falls sick when exposed to the pathogen.

(c) Four economic importance of animal disease

• It causes death of animals, leading to loss of stock and capital.
• It reduces productivity (lower milk, meat, egg and wool yield).
• It increases the cost of production through spending on drugs and veterinary care.
• It lowers the market value/quality of animals and their products; some diseases (zoonoses) are transmissible to man.

(d) Three factors that determine the degree of resistance

• The breed and heredity of the animal.
• The age and general health/nutritional status of the animal.
• Previous exposure or vaccination that confers immunity.

(e) Three conditions that may inactivate a pathogenic organism

• Exposure to high temperature/heat (e.g. boiling, pasteurisation).
• Application of disinfectants and antiseptics.
• Exposure to sunlight (ultraviolet radiation) and drying.

Detalles de la respuesta

(a) Hired labour

Hired labour refers to the workers engaged and paid wages or salaries by the farmer to perform farm operations. Such labourers are not members of the farmer family and may be employed on a permanent, casual or contract basis.

(b) Fixed capital

Fixed capital refers to the durable assets of the farm that are used again and again over a long period and are not used up in a single production cycle. Examples include land, farm buildings, tractors, machinery and farm implements.

(c) Working capital

Working capital (also called circulating or operating capital) refers to the assets that are used up within a single production cycle and must be replaced each season. Examples include seeds, fertilizers, agro-chemicals, feeds, fuel and cash for paying wages.

(d) Management

Management is the factor of production that involves organising, planning, coordinating and controlling the other factors of production (land, labour and capital) and taking decisions to achieve the farm objectives at a profit. The manager bears the risks and uncertainties of the farm business.

Detalles de la respuesta

(a) The term marketing

Marketing is the sum total of all the activities and services involved in moving agricultural produce from the producer (farmer) to the final consumer. It covers assembling, processing, storage, transportation, grading, pricing, buying and selling of the produce.

(b) Five importance of marketing in agriculture

• It moves produce from areas of surplus to areas of scarcity/need.
• It provides income to farmers and creates employment for many people.
• It stabilises prices of agricultural produce and matches supply with demand.
• It encourages increased production by ensuring farmers can sell their output.
• It makes goods available to consumers at the right time, place and form.

(c) Five marketing functions

1. Assembling/collection of produce.
2. Processing of produce.
3. Storage of produce.
4. Transportation of produce.
5. Grading and standardisation.
6. Buying and selling (exchange).

(d) Four ways marketing of agricultural produce can be encouraged

• Provision of good roads and transportation facilities.
• Provision of storage and processing facilities to reduce spoilage.
• Establishment of marketing boards and cooperative societies.
• Provision of credit facilities and reliable market information to farmers and traders.