WAEC SSCE - Agricultural Science - 2010 (Essay)

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(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).

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(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.

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(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.

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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.

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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.

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(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).

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(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

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(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) 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.