WAEC SSCE - Agricultural Science - 2010

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The causal organism of anthrax in farm animals is known as Bacillus anthracis. Anthrax is a bacterial disease that affects both animals and humans, and it is caused by the spore-forming bacteria Bacillus anthracis. The bacteria produce spores that can survive for long periods in the soil, and when ingested by animals or humans, can cause severe illness and even death. Farm animals such as cattle, sheep, and goats are particularly susceptible to anthrax infection, which can occur through ingestion of contaminated soil, feed, or water. In humans, anthrax can be contracted through direct contact with infected animals, their tissues or fluids, or through inhalation of spores. Therefore, it is important for farmers to take preventive measures such as vaccination of their animals and proper disposal of infected animal carcasses to prevent the spread of anthrax.

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The operation that takes place in a ginnery is the separation of cotton seeds from the lint. A ginnery is a factory where raw cotton is processed and separated from the seeds by a machine called a cotton gin. The cotton fibers are then used to produce textiles, while the seeds can be used to produce cottonseed oil or cottonseed cake, which is a byproduct used for animal feed. Therefore, the correct option is the separation of cotton seeds from lint.

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Détails de la réponse

Crop rotation is a farming practice that involves planting different crops in a particular field over a period of time, while mixed farming involves cultivating different types of crops and rearing animals on the same piece of land. Both of these practices are examples of cultural methods used to control pests and diseases, as they help to disrupt the life cycle of pests and prevent the build-up of diseases in the soil. On the other hand, monoculture involves planting a single crop in a field, which can lead to the build-up of pests and diseases, and therefore is not a cultural method used to control pests and diseases. Therefore, the correct answer is (A) I and II only.

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The infectious disease of livestock that is characterized by sudden death and black, bloody discharge from the nose, mouth, and eyes is known as "anthrax." Anthrax is caused by the bacteria Bacillus anthracis, which can produce spores that can survive for long periods in the soil. Livestock can become infected with anthrax by ingesting or inhaling the spores while grazing on contaminated pastures or by coming into contact with infected animals or animal products. The disease can also be transmitted to humans who come into contact with infected animals or animal products. Anthrax is a very serious disease and can cause rapid death in affected animals. Symptoms may include fever, loss of appetite, and difficulty breathing. The black, bloody discharge from the nose, mouth, and eyes is a characteristic sign of the disease. To prevent anthrax, farmers and livestock owners can vaccinate their animals and avoid grazing them on contaminated pastures. If an outbreak does occur, affected animals should be isolated and treated promptly, and strict biosecurity measures should be implemented to prevent the spread of the disease to other animals or humans.

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Détails de la réponse

In the carbon cycle, atmospheric carbon dioxide is replenished by the process of respiration. Respiration is a process in which living organisms convert organic matter into energy for their daily activities. During respiration, organisms break down carbohydrates and release carbon dioxide as a byproduct. This carbon dioxide is then released into the atmosphere and can be used by plants during photosynthesis to produce more organic matter. The other options listed are not directly involved in replenishing atmospheric carbon dioxide. Transpiration is the process by which plants release water vapor into the atmosphere, and lightning is an atmospheric discharge of electricity that can produce nitrogen oxides, which can indirectly affect the carbon cycle. Denitrification is a process by which certain bacteria convert nitrates back into nitrogen gas, and is not directly involved in the carbon cycle.

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Détails de la réponse

The average gestation period in sheep is approximately 150 days, or about 5 months. Gestation period refers to the length of time that a female animal is pregnant and carrying offspring before giving birth. During gestation, the fertilized egg develops into a fetus within the mother's uterus. In sheep, the gestation period can vary slightly depending on factors such as breed, age, and health of the mother. It is important for farmers and livestock owners to be aware of the gestation period in their animals, as it can affect the timing of breeding, feeding, and other management practices. Proper nutrition and care during gestation can also help ensure the health and well-being of both the mother and the developing offspring.

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A louse is an ectoparasite of farm animals. Ectoparasites are parasites that live on the outside of the host's body, feeding on blood or skin cells. Lice are small, wingless insects that attach themselves to the hair or feathers of animals and feed on their blood. They can cause itching, skin irritation, and reduced production in farm animals, such as cattle, sheep, and poultry. Lice are common in crowded or unhygienic conditions, making good management practices such as regular grooming, cleaning, and reducing animal density essential for their control. The other options listed, tapeworm, liverfluke, and roundworm, are all endoparasites, meaning they live inside the host's body.

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Détails de la réponse

Natural immunity can be conferred on newly-born animals through feeding with colostrum. Colostrum is the first milk produced by the mother after giving birth, and it contains high levels of antibodies that the mother has built up over time. When the newborn animal drinks colostrum, these antibodies are passed on to them and help protect against diseases. This is important because newborn animals are born with immature immune systems and are more susceptible to infections. Vaccination and antibiotics are not natural ways of conferring immunity and do not involve the transfer of antibodies from the mother to the newborn animal. Strict sanitation practices can help reduce the risk of infection, but do not provide the same level of protection as natural immunity.

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The farming practice that does not expose soil to agents of erosion is "crop rotation". Crop rotation is a method of farming where crops are planted in a specific sequence over time to maintain soil fertility and prevent erosion. On the other hand, bush burning, land clearing, and overgrazing all expose the soil to agents of erosion such as wind and rain. Bush burning and land clearing remove plant cover and leave the soil exposed to erosion. Overgrazing also removes vegetation cover and weakens the soil structure, making it more susceptible to erosion.

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The least important factor in selecting a site for a fish-pond is the availability of manure. While manure can be beneficial for the growth of aquatic plants and the production of natural food for fish, it is not essential for the establishment of a successful fish-pond. The topography of the site, soil type, and availability of water are all crucial factors in selecting a suitable location for a fish-pond. The topography of the site will determine the water flow, while the soil type will determine the ability of the pond to retain water. Availability of water is obviously essential since it is the primary resource in a fish-pond, and it should be in sufficient quantities and quality. In summary, while manure can be a useful resource for a fish-pond, it is not a crucial factor in selecting a site for a fish-pond, and the topography of the site, soil type, and availability of water should be given higher priority.

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Disease resistance is an important aspect of crop improvement because it enables crops to withstand attacks from pathogens. This means that crops are better able to resist diseases, which can help to increase yields and reduce losses due to plant diseases. By breeding crops that are resistant to specific diseases, farmers can reduce their dependence on chemical pesticides and improve the sustainability of their farming practices.

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Détails de la réponse

High temperature and pressure convert sandstone to quartzite. Sandstone is a sedimentary rock composed of sand-sized mineral particles or rock fragments. When sandstone undergoes high temperature and pressure, the individual grains of sand are fused together, forming a harder and more compact rock called quartzite. This process, known as metamorphism, causes the sand grains to recrystallize and fuse together, creating a dense and durable rock that is resistant to erosion and weathering. Quartzite is mainly composed of quartz, with minor amounts of other minerals such as feldspar, mica, and iron oxide. It is commonly used as a construction material due to its strength and durability.

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Mould growth on cereal grains stored in damp conditions is caused by a fungus. Mould is a type of fungus that grows on food items in damp conditions. Cereal grains such as rice, maize, and wheat are particularly susceptible to mould growth when stored in damp conditions. The fungus grows on the surface of the grains, producing a furry or powdery coating that can contaminate the grains and make them unsafe for consumption. This is why it is important to store cereal grains in dry conditions to prevent mould growth.

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Accounts payable is a liability to a farm. It refers to the amount of money a farm owes to its suppliers or creditors for goods or services that have been received but not yet paid for. This means that the farm has a legal obligation to pay the suppliers or creditors for their goods or services within an agreed period of time. Failure to pay the accounts payable within the agreed period of time can lead to late payment fees, damaged credit ratings and strained business relationships. Therefore, accounts payable should be closely monitored and managed to ensure that the farm maintains good financial health.

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Détails de la réponse

Rabbits are herbivorous animals, which means they feed on plants. However, plants contain complex carbohydrates, such as cellulose, that cannot be easily digested by rabbits. To overcome this problem, rabbits have an enlarged caecum, which is a part of the digestive system that is responsible for breaking down tough plant materials. The caecum is home to a population of bacteria that help to ferment and break down cellulose into simpler compounds that the rabbit can digest. Therefore, the correct option is "enlarged caecum".

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Détails de la réponse

Streak disease of maize is caused by a virus. The virus is transmitted by several species of leafhoppers. The symptoms of the disease include the appearance of long, narrow, yellow or orange streaks on the leaves of infected plants. As the disease progresses, the streaks may turn brown and the leaves may become curled and distorted. The virus can cause significant damage to maize crops, reducing yields and quality.

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Détails de la réponse

The land tenure system for individual ownership is the freehold system. In this system, an individual or entity owns a piece of land and has complete rights over it, including the right to sell, lease, or pass it on to heirs. The ownership is perpetual and can be transferred freely from one owner to another. This system provides security of tenure to the landowner and encourages long-term investment and sustainable use of the land. Other land tenure systems such as the land pledge system, leasehold system, or tenancy at the will of government, do not provide the same level of ownership rights and may be subject to limitations or restrictions by the government or other parties.

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Growing disease-resistant crops promotes agricultural development because it helps farmers protect their crops from being destroyed by diseases. When crops are resistant to diseases, farmers can achieve higher yields, reduce losses, and increase their income. This can lead to greater food security and economic growth. Planting late-maturing crop varieties also promotes agricultural development because it allows farmers to harvest their crops at a time when market prices are higher. Late-maturing crops take longer to mature and ripen, which means that they can be harvested later in the season when there is less supply and higher demand for the crop. This can help farmers get a better price for their crops and increase their income. Banning the importation of pesticides may not necessarily promote agricultural development because it could limit the options available to farmers for controlling pests and diseases. However, promoting the use of safer, more sustainable pest management practices such as integrated pest management (IPM) can promote agricultural development. IPM involves using a combination of techniques such as crop rotation, biological controls, and natural predators to manage pests and diseases while minimizing the use of synthetic pesticides. Encouraging a communal land tenure system can promote agricultural development by providing farmers with greater access to land. When land is owned collectively by a community, farmers who may not have access to their own land can still cultivate and harvest crops. This can increase food production, promote social cohesion, and help to reduce poverty. However, communal land tenure systems may also face challenges such as conflicting land use priorities, disputes over land ownership, and difficulties in securing financing for agricultural investments.

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Détails de la réponse

Increased butter-fat percentage is not important in beef cattle breeding. This is because butter-fat content is more relevant to dairy cattle breeding, which is aimed at producing milk with high fat content. In beef cattle breeding, the focus is on producing animals with a high yield of lean meat and good feed conversion efficiency. Lean meat yield is important because it is the part of the carcass that is consumed by humans, while feed conversion efficiency is important because it determines how efficiently the animal converts feed into muscle. High fertility is also important in beef cattle breeding because it ensures that the herd size can be maintained or increased. Therefore, while all the options listed may be important in different types of animal breeding, increased butter-fat percentage is not relevant to beef cattle breeding.

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Sprinkler irrigation is advantageous because it allows for large areas of land to be irrigated, which means that farmers can cover a lot of ground and water more crops at once. This can be particularly helpful for large-scale commercial farmers who need to irrigate vast areas of land. Additionally, the system is relatively easy to install, making it accessible to a wide range of farmers, including smallholder farmers. While it may not be affordable for all peasant farmers, it can still be a viable option for many.

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Détails de la réponse

The main reason for establishing game reserves is to prevent wildlife from becoming extinct. Game reserves are areas of land that are set aside for the conservation of wildlife and their habitats. They are created to protect wildlife from extinction, which can result from poaching, habitat destruction, and other human activities. By creating game reserves, governments and conservation organizations hope to provide a safe haven for wildlife to thrive and to ensure that future generations can enjoy these animals in their natural habitats.

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Détails de la réponse

The crops that grow best in the savanna zones of West Africa are cotton, millet, and groundnut. This is because these crops are well adapted to the dry conditions and high temperatures found in the savanna. Cotton is a crop that requires a warm and dry climate to grow, and the savanna provides such conditions. Millet is a drought-resistant grain crop that can grow in poor soils and is well suited for the savanna's dry conditions. Groundnut, also known as peanut, is a legume that can fix nitrogen in the soil, making it a good crop to grow in areas where the soil is poor. Cocoa, kola, oil palm, guinea corn, banana, and rubber are not as well adapted to the dry conditions of the savanna, and may require more water or specific soil conditions to grow properly. Therefore, they may not be the best crops to grow in the savanna zones of West Africa.

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A farmstead should be located close to a source of water for several reasons, but erosion of farm structures is not one of them. One reason for locating a farmstead close to a source of water is to reduce overhead costs. If a farmer has to transport water over long distances, this can be expensive and time-consuming. By locating the farmstead near a water source, the farmer can save money and use the time and resources to focus on other aspects of farming. Another reason is to operate an efficient irrigation system. Irrigation is essential in dry areas where there is not enough rainfall to support crops. By locating the farmstead close to a water source, the farmer can easily pump water to irrigate the crops, which will increase yields and improve the quality of the produce. Processing of farm produce is another reason for locating a farmstead close to a water source. Many farm products require washing and cleaning before they can be sold. By locating the farmstead near a source of water, farmers can easily access water for cleaning and processing their produce. In summary, while there are several reasons for locating a farmstead near a source of water, erosion of farm structures is not one of them. Instead, the main reasons include reducing overhead costs, operating an efficient irrigation system, and processing farm produce.

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The provision of labour is not a role of the government in agricultural production. Labour is provided by individuals who work on farms and other agricultural enterprises. The government's role in agricultural production typically involves creating policies and programs that support farmers and ensure food security for the population. This includes providing subsidies, building storage facilities to preserve crops, and providing loans and credits to farmers to help them purchase inputs and improve their operations. Additionally, the government may engage in research and development to improve agricultural techniques and technologies, as well as regulate the industry to ensure safety and sustainability. However, the provision of labour is not a role that the government typically plays in agricultural production.

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The extension method that will benefit only the literate farmers is newspapers. This is because newspapers are primarily a written medium, and so farmers who are literate and can read and understand the information presented in the newspaper will benefit from it. On the other hand, farmers who are not literate may struggle to benefit from newspapers, as they may not be able to read the information or understand it fully. Radio and television may be more accessible to illiterate farmers, as they are primarily audio-visual mediums, and demonstration may be a more hands-on approach that does not rely on reading or writing skills.

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Détails de la réponse

Training of yam vines is important to increase photosynthesis. Training involves arranging the yam vines in a specific pattern on a trellis or support system, which helps to expose more leaves to sunlight. This results in an increase in photosynthesis, which is the process by which plants use sunlight to produce energy and food for growth. By increasing photosynthesis, yam plants can produce more and larger tubers, leading to increased yields. Additionally, training of yam vines can help to suppress weed growth by reducing competition for nutrients and sunlight. It can also make it easier to navigate through the farm during planting, weeding, and harvesting, as well as prevent rodent attacks by making it difficult for them to access the vines. Overall, training of yam vines is an important practice that can result in increased yields, improved plant health, and easier farm management.

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Détails de la réponse

Détails de la réponse

The milk let down hormone in farm animals is called oxytocin. Oxytocin is a hormone released by the pituitary gland that stimulates the contraction of smooth muscles in the mammary gland, causing milk to be released into the ducts leading to the nipple. It is released in response to stimulation of the nipple, such as the suckling of young by a nursing animal. This hormone is important for milk production in farm animals, as it helps to ensure that milk is efficiently released during milking.

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The major raw material of the paper industry is pulp. Pulp is made by breaking down wood into its component fibers, which can then be used to make paper. The process of making pulp involves first removing the bark and other unwanted materials from the wood, and then grinding it into a fine pulp using a chemical or mechanical process. Once the pulp has been made, it can be used to make a wide variety of paper products, including newspapers, magazines, books, and packaging materials. Pulp can also be made from other sources, such as recycled paper, but wood pulp is still the most common raw material used in the paper industry.

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The biotic factor that derives much benefit from livestock and reduces productivity is a parasite. A parasite is an organism that lives on or within another organism, known as the host, and benefits at the host's expense. Livestock can be hosts to a variety of parasites, such as ticks, lice, and worms, which can cause harm to the animals and reduce productivity. Parasites can lead to weight loss, anemia, reduced milk production, and even death in severe cases. Additionally, parasites can be transmitted from livestock to humans, leading to health problems. Therefore, it is important for livestock producers to manage parasite infestations through various methods, such as deworming and sanitation, to ensure the health and productivity of their animals.

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The survey instrument used for measuring horizontal and vertical angles on the field is the theodolite. It is an optical instrument that has a rotating base and a telescope mounted on it. The theodolite is used to measure angles between two points on the ground, which is important in surveying and construction work. The horizontal angle is measured by rotating the theodolite on its base, while the vertical angle is measured by tilting the telescope up or down. The theodolite is a precise instrument that is commonly used by surveyors and engineers to measure angles and distances accurately.

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The objectives of farm mechanization are the goals or aims that are intended to be achieved through the use of farm machinery. These objectives include increasing farm yield, performing farm operations quickly and more efficiently, and improving the quality of farm produce. However, the option "produce disease-resistant crop varieties" does not relate to the objectives of farm mechanization because it is concerned with the development of crop varieties that are resistant to diseases, which is a function of plant breeding and genetics, and not farm mechanization. Therefore, the correct answer is option D, "produce disease-resistant crop varieties".

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Détails de la réponse

Détails de la réponse

Corms, rhizomes, and tubers are examples of underground stems. These are specialized plant structures that grow underground and serve as storage organs for the plant. They help the plant survive during unfavorable conditions, such as drought or winter, by storing nutrients and energy for future growth. Corms are short, swollen underground stems that are used for food storage. Rhizomes are horizontal, underground stems that grow along or just beneath the surface of the soil, producing roots and shoots at intervals. Tubers are enlarged, fleshy underground stems that grow at the end of stolons and store nutrients for the plant. Examples of plants that have these underground stems are taro, ginger, potato, and yam.

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All three problems are associated with agricultural marketing in West Africa: I. Seasonality of produce: Farmers often experience a glut of produce during the peak harvest season, which leads to low prices due to oversupply. During the off-season, however, prices rise as demand increases but farmers may not have enough produce to meet this demand. II. Transportation of produce: Due to poor road infrastructure and inadequate transportation systems, farmers often find it difficult to transport their produce to markets. This can result in spoilage and loss of quality of produce, which negatively affects the prices that they receive. III. Access to credit: Farmers in West Africa often lack access to credit, making it difficult for them to finance their operations and invest in new technologies that would improve their productivity. Without credit, farmers may not be able to purchase inputs such as fertilizers and pesticides, which can negatively affect the quality and quantity of their produce. Therefore, the correct answer is I, II and III.

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Feeds given to animals solely to sustain their live weight is called a maintenance ration. The purpose of a maintenance ration is to provide the necessary nutrients for an animal to maintain its body weight and support basic bodily functions, such as respiration and digestion. This type of ration is typically given to animals that are not being raised for production purposes, such as breeding stock or animals that are not yet old enough for production. The amount and composition of a maintenance ration will vary depending on the animal's species, age, weight, and level of physical activity.

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Détails de la réponse

The answer is "seeds have short period of viability". Weeds are known for their ability to produce numerous seeds and have an aggressive growth habit, which allows them to outcompete other plants for resources. They may also be resistant to trampling, meaning that they can survive even when repeatedly stepped on or otherwise disturbed. However, the viability of their seeds can vary greatly depending on the species, and some weed seeds can remain viable in the soil for many years. So, the option that is not a characteristic of weeds is "seeds have short period of viability".

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Tilapia is a fish species that is found in fresh water. It is a popular fish in aquaculture because it is relatively easy to raise and adapts well to different types of water environments. Tilapia is also a good source of protein and is relatively inexpensive compared to other types of fish. The other options, sardine, salmon, and herring, are all saltwater fish species. They are typically found in oceans and seas and are often caught by commercial fishing fleets.

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The most common grazing system in West Africa is continuous grazing. This is a system where animals are allowed to graze on a piece of land continuously without any form of restriction. The animals are not moved to different areas for grazing but rather allowed to roam freely within the same location. This system is common in West Africa due to its simplicity and low cost. However, it can lead to overgrazing, soil erosion, and reduced productivity of the land.

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The main sources of farm power in West Africa are human, animal, and mechanical power. Human power refers to the use of physical labor by humans to perform agricultural tasks such as planting, weeding, and harvesting. This has been a traditional source of farm power in West Africa for centuries and is still widely used today. Animal power involves using animals such as oxen, horses, and donkeys to perform farm work. These animals are typically harnessed to plows, carts, and other implements and can greatly increase the efficiency of agricultural operations. Mechanical power is the use of machines such as tractors, combines, and irrigation pumps to perform farm work. This type of power is becoming increasingly common in West Africa as the region modernizes and farmers have greater access to technology. While wind and solar power may be used in some areas of West Africa to generate electricity for farm operations, they are not currently major sources of farm power in the region. In summary, the main sources of farm power in West Africa are human, animal, and mechanical power, with each having its own advantages and disadvantages depending on factors such as the type of crop, soil conditions, and available technology.

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Détails de la réponse

Stylosanthes gracilis is a pasture legume. Pasture legumes are important components of grazing systems because they provide high-quality forage for livestock and can also fix nitrogen in the soil, which benefits the growth of other plants in the pasture. Stylosanthes gracilis is a tropical and subtropical legume that is commonly used in grazing systems due to its high protein content and ability to grow well in poor soil conditions. It is also drought-tolerant and can grow in areas with low rainfall. The other options listed, namely Cynodon pletostachyus, Panicum maximum, and Pennisetum purpureum, are all grass species commonly used in grazing systems, but they are not legumes.

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The function of the mouldboard in a mouldboard plough is to invert the furrow slice. A mouldboard plough is a tillage equipment used to turn the soil over in preparation for planting. The mouldboard is a curved metal plate located at the rear of the ploughshare that is responsible for lifting and turning over the furrow slice. As the plough moves forward, the share cuts a vertical slice of soil, and the mouldboard then lifts and turns the soil slice over, completely inverting it. This helps to bury surface vegetation and crop residue, aerate the soil, and bring nutrients to the surface. The mouldboard also helps to create a more level surface for planting and to reduce soil erosion by breaking up compacted soil layers.

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(a) Four ways weeds are beneficial to the farmer

1. They protect the soil surface from erosion and reduce the impact of rain drops.
2. When ploughed under (as green manure) they add organic matter and nutrients to the soil.
3. Some weeds are legumes that fix nitrogen and improve soil fertility.
4. They serve as fodder/feed for livestock and some are used as medicinal herbs and vegetables (they also serve as cover crops that conserve soil moisture).

(b) Classification of insect-pests by mode of feeding

(c) Three ways pasture can be made available to cattle

1. By allowing the animals to graze freely on natural or established grassland (grazing).
2. By cutting the grass/forage and carrying it to feed the animals (cut-and-carry / soilage/zero grazing).
3. By conserving forage as hay or silage and feeding it during the dry season when fresh pasture is scarce.

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(a) Three functions of a farm manager

1. Planning and organising the farm operations and resources.
2. Directing, supervising and coordinating the farm workers.
3. Keeping farm records, controlling finances and taking decisions to make the farm profitable.

(b) Terms in agricultural economics

1. Appreciation: the increase in the value of a farm asset over a period of time, for example land whose value rises with time.
2. Salvage value: the estimated value (scrap or resale value) of a farm asset at the end of its useful life when it can no longer be used for production.
3. Farm budget: a written plan or estimate of the expected income and expenditure of a farm business over a given period, used to guide the use of resources.
4. Farm inventory: a complete list of all the assets (property) and liabilities of a farm, with their quantities and money values, taken at a particular date.

(c) Five qualities of a good agricultural extension agent

1. He should be knowledgeable and well trained in agriculture.
2. He should be patient, friendly and able to communicate clearly with farmers.
3. He should be honest, hard-working and of good character.
4. He should be able to speak the local language of the farmers.
5. He should be humble, willing to learn from farmers and ready to demonstrate practically what he teaches.

Détails de la réponse

(a) Six benefits derived from growing ornamental plants

1. They beautify and improve the appearance of homes, offices and surroundings.
2. They are a source of income when sold in the florist trade.
3. They provide shade and help to cool the environment.
4. They serve as windbreaks and help to control soil erosion.
5. They purify the air by taking in carbon dioxide and giving out oxygen.
6. They are used for decoration at ceremonies and provide recreational and educational value.

(b) Four symptoms of cassava mosaic disease

1. Yellow and green patchy (mosaic) discolouration of the leaves.
2. Distortion, curling and reduction in size of the leaves.
3. Stunted growth of the whole plant.
4. Poor development of tubers, giving low yield.

(c) Terms in forest management

1. Selective exploitation: the felling and removal of only the mature and economically valuable trees from the forest, leaving the young and immature ones to continue growing.
2. Regeneration: the renewal or replacement of harvested/removed trees in the forest, either naturally (from seeds and coppices) or artificially (by replanting), so that the forest is maintained.
3. Taungya farming: a system in which farmers are allowed to grow food (arable) crops in between young forest tree seedlings, tending both the crops and the young trees until the trees form a canopy.

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(a)(i) Law of diminishing returns. It states that as successive (equal) units of a variable input (such as fertiliser or labour) are added to a fixed input (such as a fixed piece of land), the extra (marginal) output first rises, then reaches a maximum, and thereafter declines. In other words, beyond a certain point each additional unit of the variable input yields a progressively smaller addition to total output.

(ii) Main cause of diminishing returns. It arises because one factor of production (the land) is fixed while the other factor is varied. As more of the variable input is crowded onto the same fixed area, each extra unit has proportionately less of the fixed factor to work with, so its productivity falls. The fixed factor becomes over-utilised (for example the soil nutrients, space, moisture and light per plant become inadequate), and eventually the marginal product declines.

(b) Depreciation of the combine harvester.

Cost price in 1990 = N100,000.00; resale price in 2000 = N30,000.00; useful life = 2000 \(-\) 1990 = 10 years.

(i) Salvage value = the resale (scrap) value at disposal = N30,000.00.

(ii) Total depreciation = cost price \(-\) salvage value

\[ = N100{,}000 - N30{,}000 = N70{,}000.00 \]

(iii) Annual depreciation (straight-line method) = total depreciation \(\div\) number of years

\[ = \frac{N70{,}000}{10} = N7{,}000.00 \text{ per year} \]

(c) Seven problems of agricultural extension services in West Africa:

1. Inadequate funding of extension programmes by government.
2. Shortage of well-trained and qualified extension personnel.
3. Poor transport and communication facilities, making rural areas hard to reach.
4. High farmer-to-extension-agent ratio, so agents are overworked and cannot reach all farmers.
5. High level of illiteracy among farmers, which hinders the adoption of new techniques.
6. Poor linkage between research institutes, extension agents and farmers, so improved technologies do not reach the farm.
7. Inadequate teaching aids, demonstration materials and improved inputs for extension work.

Détails de la réponse

(a) Distinguish between the systems

(i) Monoculture and monocropping

Monoculture is the growing of the same single crop on the same piece of land year after year, while monocropping (sole cropping) is the growing of only one crop on a piece of land in a given season (one crop at a time, but the crop may change from season to season).

(ii) Shifting cultivation and land rotation

In shifting cultivation the farmer cultivates a piece of land until its fertility declines, then abandons it and moves with his home to a new piece of land, whereas in land rotation the farmer has a fixed home and rotates cultivation among several plots, farming one and leaving the others to fallow, then returning to them in turn.

(b) Four problems of commercial agriculture in West Africa

1. Inadequate capital to finance large-scale production.
2. Poor storage, processing and marketing/transport facilities.
3. Land tenure problems that make large parcels of land hard to acquire.
4. Shortage of skilled labour and high cost of machinery and inputs (pest, disease and unfavourable weather are also acceptable).

(c) Four uses of the farm tractor

1. Ploughing and harrowing the land.
2. Ridging and planting.
3. Transporting farm inputs and produce.
4. Driving other machines through its power take-off (spraying, harvesting, water pumping).

(d) Four indigenous methods of land preparation

1. Bush clearing with cutlass and hoe.
2. Bush burning.
3. Making heaps and ridges manually.
4. Stumping and packing of debris by hand.

Détails de la réponse

(a) Definitions and (b) one example of each

(c) Four steps involved in silage making

1. Harvesting/cutting: cut the green forage (grass or legume) at the right stage of growth.
2. Chopping and filling: chop the forage into small pieces and pack it into the silo, compressing it firmly to drive out air.
3. Sealing/compaction: cover and seal the silo air-tight so that anaerobic fermentation (souring) can take place.
4. Storage/curing: leave the sealed material to ferment and cure for some weeks until it becomes silage ready for feeding.

Détails de la réponse

(a) Effects on agricultural production

(i) Agricultural education and extension: they teach farmers improved farming methods and carry research findings to them, leading to the use of better seeds, fertilisers and machinery. This raises yield, improves the quality of produce, encourages adoption of new technology and increases the farmers' income and standard of living.

(ii) Environmental degradation: degradation such as erosion, deforestation, desertification and pollution destroys the fertile top soil and reduces the area of good farmland. This lowers soil fertility and crop yield, kills useful organisms, reduces water availability and generally reduces total agricultural production.

(b) Three problems of communal land tenure system

1. Land cannot easily be used as security (collateral) to obtain loans.
2. Individuals are discouraged from making permanent improvements because they do not own the land outright.
3. Fragmentation and disputes over ownership make large-scale mechanised farming difficult.

(c) Four components of an incubator

1. Heat source (heater/lamp)
2. Thermostat/thermometer (temperature regulator)
3. Egg trays/racks with turning device
4. Humidity/water tray and ventilation holes

(d) Storage structure for each produce

• (i) Yam tubers: yam barn.
• (ii) Cowpea seeds: silo / rhumbu (crib) / air-tight drum.
• (iii) Fresh fish: cold room / refrigerator (freezer).

Détails de la réponse

(a) Chemical weathering of rocks

Chemical weathering is the breaking down and decay of rocks through chemical reactions that change the mineral composition of the rock, so that the rock is altered into new substances and eventually broken into fine soil particles. It is aided by water, oxygen, carbon dioxide and warmth.

(b) Four processes of chemical weathering

1. Solution: water dissolves soluble minerals in the rock (for example rock salt and limestone), removing them and weakening the rock.
2. Carbonation: rain water dissolves carbon dioxide to form weak carbonic acid, which reacts with limestone (calcium carbonate) to form soluble calcium bicarbonate that is washed away.
3. Hydrolysis: water reacts chemically with rock minerals such as feldspar, changing them into soft clay minerals.
4. Oxidation: oxygen in air and water reacts with minerals containing iron, forming reddish-brown iron oxides (rusting) that make the rock crumble. (Hydration, the absorption of water by minerals causing them to swell and flake, is also acceptable.)

(c) Four ways soil temperature is important for crop growth

1. It affects the germination of seeds; suitable warmth is needed before seeds can sprout.
2. It controls the rate of absorption of water and nutrients by plant roots.
3. It affects the activity of soil micro-organisms that decompose organic matter and release nutrients.
4. It influences the rate of chemical reactions, nutrient availability and general growth of the crop (very high or very low temperatures slow or stop growth).

Détails de la réponse

(a) Four breeds of chicken used for commercial egg production

1. White Leghorn
2. Rhode Island Red
3. Black Australorp
4. New Hampshire (Isa Brown/other layer strains are also acceptable)

(b) Two functions of each dietary component

(c) Four advantages of the intensive system of rearing ruminants

1. Many animals can be reared in a small space.
2. The animals are closely supervised, so diseases and pests are easily detected and controlled.
3. Feeding is controlled and balanced, giving faster growth and higher productivity.
4. Records are easy to keep and the animals are protected from theft, predators and bad weather.

Détails de la réponse

(a) Reasons for the practices

(i) Southward movement of herdsmen to the rain forest zone in the dry season

1. To find fresh pasture/grass for the animals, since grasses in the north dry up in the dry season.
2. To obtain drinking water for the animals from the streams and rivers of the forest zone.

(ii) Preference for simple farm tools over machinery

1. Simple tools are cheap to buy and maintain, while machinery is very costly.
2. The farms are small and scattered on rough or fragmented land where machines cannot easily be used, and the farmers lack the skill and capital to run machines.

(b) Movement of herdsmen: problems and solutions