WAEC SSCE - Agricultural Science - 1994 (Essay)

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Process of egg formation in poultry

Egg formation takes place in the reproductive tract of the hen and takes about 24 to 26 hours to complete one egg.

1. Ovary: The yolk (ovum) develops and is stored in follicles on the ovary. When a yolk is mature it is released (ovulation).
2. Infundibulum (funnel): The released yolk is picked up by the funnel-shaped infundibulum. Fertilization by sperm, if the hen has mated, takes place here.
3. Magnum: As the yolk moves down, the thick albumen (egg white) is secreted and added around it.
4. Isthmus: The two shell membranes (inner and outer) are formed around the albumen here.
5. Uterus (shell gland): Water and mineral salts are added to the albumen (plumping), and calcium carbonate is deposited to form the hard shell. Shell colour or pigment is also added at this stage.
6. Vagina and cloaca: The completed egg passes into the vagina and is finally laid through the vent (oviposition), usually with the broad end first.

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(a) Farm surveying

Farm surveying is the process of measuring, mapping and recording the relative positions, boundaries, sizes, shapes and areas of a piece of farmland, and representing them to scale on paper.

(b) (i) Six surveying instruments

• Measuring (surveyor's) tape
• Ranging pole
• Surveyor's chain (Gunter's chain)
• Prismatic compass
• Theodolite
• Dumpy level (arrows/pins and pegs are also used)

(ii) Short notes on four instruments

• Ranging pole: A straight pole painted in alternate red and white bands. It is used to mark points and to align or range straight lines during a survey.
• Measuring tape: A flexible steel or linen tape graduated in metres. It is used to measure distances between points on the ground.
• Prismatic compass: A small hand-held instrument containing a magnetic needle. It is used to measure the bearings or directions of survey lines.
• Theodolite: A precise instrument mounted on a tripod, used to measure horizontal and vertical angles accurately in detailed surveys.

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Short notes on the factors of agricultural production

(a) Land

Land is the natural resource or free gift of nature on which agricultural production takes place. It includes the soil, water bodies, forests and mineral deposits. Land is fixed in supply and immobile, and its quality varies from place to place. Its reward is rent.

(b) Capital

Capital is the man-made wealth used in production. It includes money, farm tools, machinery, buildings, seeds, fertilizers and livestock. Capital is used to acquire other inputs and to expand production; it can be increased and it depreciates with use. Its reward is interest.

(c) Labour

Labour is the human physical and mental effort used in production. It may be skilled or unskilled and supplies the workforce that carries out farm operations such as planting, weeding and harvesting. Its reward is wages or salary.

(d) Farm manager

The farm manager is the person who organises and coordinates the other factors of production. He plans, directs and controls the farm business, takes decisions, keeps records and bears the risks of production to ensure efficient use of resources. His reward is profit.

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Named ruminant: Cattle (cow)

Digestion in cattle

1. The cow plucks grass, chews it only slightly and swallows it. The food is mixed with much saliva and passes through the oesophagus into the rumen and reticulum.
2. In the rumen, bacteria, protozoa and fungi ferment cellulose in the grass. These micro-organisms produce cellulase, which the cow itself does not produce. Some volatile fatty acids formed are absorbed through the rumen wall.
3. The partly fermented food is formed into balls called cud. During rest, the cud is regurgitated from the reticulum through the oesophagus to the mouth by reverse peristalsis.
4. In the mouth, the cud is chewed thoroughly and mixed again with saliva. It is then re-swallowed. This repeated chewing and swallowing is called rumination.
5. The re-swallowed food passes to the omasum. Its many folds grind the food further and absorb water and some mineral salts.
6. Food then enters the abomasum, the true stomach. It secretes hydrochloric acid and digestive enzymes, especially pepsin, which digest proteins, including proteins of the micro-organisms.
7. In the small intestine, bile, pancreatic juice and intestinal enzymes complete digestion. Digested nutrients are absorbed through the villi into the blood and lymph.
8. Some remaining fibre is acted upon by micro-organisms in the caecum and large intestine. Water is absorbed in the large intestine, while undigested residue is expelled through the anus as faeces or dung.

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(a) Land tenure system and four examples

Land tenure system is the system of customs and laws by which land is owned, acquired, held, controlled and used by an individual or a community.

Four examples are:

• Inheritance (land passed down from parents to children).
• Purchase / freehold (outright buying of land).
• Lease / leasehold (land held for a fixed period on payment).
• Communal ownership (land owned by a whole community); rent/tenancy, gift and pledge are other examples.

(b) (i) Land Use Decree

The Land Use Decree (Land Use Act) of 1978 is a Nigerian law that vests all land within a state in the Governor of that state, who holds it in trust for the people. Land is granted to individuals and organisations through a Certificate of Occupancy; urban land is controlled by the state Governor and rural land by the Local Government.

(ii) Two advantages and two disadvantages

Advantages

• It makes land more easily available for development and government projects.
• It reduces land litigation and disputes, and a Certificate of Occupancy can be used as collateral for loans.

Disadvantages

• Obtaining a Certificate of Occupancy is often slow, costly and bureaucratic.
• Government can revoke land with inadequate compensation, and excessive government control discourages large-scale private acquisition.

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(a) Natural grassland

Natural grassland is an area of land that is naturally covered with grasses, herbs and a few scattered trees or shrubs which grow on their own, without being deliberately planted or cultivated by man.

(b) Five characteristics of natural grassland

• It is dominated by grasses and grows naturally without cultivation.
• It contains a mixture of different grass species together with some pasture legumes.
• It regenerates on its own after grazing, cutting or burning.
• It is commonly found in areas of moderate to low rainfall (the savanna) and may carry scattered trees and shrubs.
• It is used mainly for the grazing of livestock and shows seasonal changes in growth.

(c) Four grasses and three pasture legumes commonly found in natural grasslands

Grasses:

• Guinea grass (Panicum maximum)
• Elephant grass (Pennisetum purpureum)
• Star grass (Cynodon species)
• Gamba/giant grass (Andropogon species)

Pasture legumes:

• Centro (Centrosema pubescens)
• Stylo (Stylosanthes species)
• Tropical kudzu (Pueraria phaseoloides)

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(a) Demand, supply and the laws governing them

Demand is the quantity of a commodity that consumers are willing and able to buy at a given price at a particular time. The law of demand states that, other things being equal, the higher the price of a commodity, the lower the quantity demanded, and the lower the price, the higher the quantity demanded.

Supply is the quantity of a commodity that producers or sellers are willing and able to offer for sale at a given price at a particular time. The law of supply states that, other things being equal, the higher the price of a commodity, the higher the quantity supplied, and the lower the price, the lower the quantity supplied.

(b) Implications of demand and supply on agricultural production

• When the price of farm produce is high, farmers are encouraged to produce more, thereby increasing supply.
• When supply exceeds demand (a glut), prices fall, farmers earn less and may reduce production in the next season.
• When demand exceeds supply (scarcity), prices rise and this encourages increased production.
• The perishable and seasonal nature of farm produce causes price fluctuations that affect farmers' incomes.
• Demand and supply guide the farmer on what crop to grow and how much to produce, and help government to plan price-stabilization and storage policies.

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(a) Taungya system

The taungya system is a method of combined forestry and crop production in which farmers are allowed to grow arable food crops in between young forest tree seedlings on forest land. The farmers tend both their crops and the young trees until the trees form a canopy, after which cropping stops.

(b) Five conditions that favour the practice of the taungya system in Nigeria

• Availability of forest land or forest reserve to be planted with trees.
• Shortage of farmland (land hunger) that makes farmers willing to use forest land.
• Availability of willing farmers who can supply the needed labour.
• Suitable food crops that do not compete strongly with the young trees for light and nutrients.
• Good cooperation and agreement between the forestry department and the farmers, and a climate suitable for both trees and crops.

(c) Two advantages of the system to each party

(i) To the farmer

• He obtains fertile forest land to grow food crops free of charge or at low cost.
• He earns income and food from the crops produced, and gains employment.

(ii) To the forester

• The cost of raising and tending the forest plantation is reduced because the farmers weed and care for the young trees.
• It ensures the successful establishment of the forest plantation and reduces weed growth and fire risk.

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Four climatic factors that affect agricultural production in Nigeria

• Rainfall: The amount, distribution and reliability of rainfall determine the type of crops grown and the length of the growing season. Adequate, well-distributed rainfall gives good yields, while too little causes drought and too much causes flooding, leaching and erosion.
• Temperature: Temperature affects germination, growth, flowering and ripening of crops and the distribution of animals and plants. Each crop has an optimum temperature range; very high or very low temperatures reduce growth and yield.
• Sunlight (solar radiation): Sunlight supplies the energy for photosynthesis, by which plants manufacture food. The intensity and duration (day length) of sunlight influence flowering, fruiting and the overall yield of crops.
• Wind: Moderate wind aids pollination, seed dispersal and drying of produce. However, strong winds cause lodging of crops, soil erosion, increased evaporation and can spread pests and diseases.

Relative humidity, which affects transpiration and the incidence of pests and diseases, is another important climatic factor.

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(a) Irrigation

Irrigation is the artificial application of water to the soil or crops to supplement rainfall so as to provide enough moisture for plant growth.

(b) Six sources of water for irrigation

• Rivers
• Streams
• Lakes
• Dams and reservoirs
• Boreholes and wells (underground water)
• Harvested rain water (springs and ponds are also sources)

(c) Three reasons why irrigation schemes are necessary in Nigeria

• To make crop production possible in the dry season and all year round.
• To supplement the inadequate and unreliable rainfall, especially in the northern (arid and semi-arid) parts.
• To bring dry, otherwise unproductive land into cultivation and increase food production.

(d) Sprinkler versus surface irrigation

Two similarities

• Both are methods of supplying water artificially to crops.
• Both help to increase crop yield and make dry-season farming possible.

Three differences