WAEC SSCE - Agricultural Science - 1996 (Essay)

Détails de la réponse

(a)(i) The law of supply in relation to agricultural production

The law of supply states that, all other factors remaining constant, the higher the price of an agricultural produce, the greater the quantity that producers are willing and able to offer for sale; and the lower the price, the smaller the quantity offered for sale. In other words, the quantity supplied of an agricultural produce varies directly (positively) with its price.

(a)(ii) Supply schedule and supply curve for maize

A supply schedule is a table showing the different quantities of a produce that farmers are willing to supply at different prices. The schedule below is for a named agricultural produce, maize (price in naira per basket):

When these points are plotted, with price on the vertical axis and quantity supplied on the horizontal axis, they give the supply curve below:

The supply curve SS slopes upward from left to right, confirming the law of supply: as the price of maize rises from \(\mathrm{N}4\) to \(\mathrm{N}10\), the quantity supplied rises from 20 to 80 baskets. The relationship is linear here, with a constant slope of \(\dfrac{10-4}{80-20}=\dfrac{6}{60}=0.1\) naira per basket, so every extra \(\mathrm{N}2\) in price calls forth an additional 20 baskets of maize.

(b) Five causes of change in supply of an agricultural produce

1. Changes in the cost of production - a fall in the price of inputs such as fertiliser, seeds and labour lowers production costs and increases supply, while a rise reduces supply.
2. Changes in weather and climatic conditions - favourable rainfall and sunshine raise yields and supply, whereas drought or flooding reduces them.
3. Changes in the technique (technology) of production - improved farming methods, mechanisation and better crop varieties raise output and increase supply.
4. Incidence of pests and diseases - outbreaks that attack crops or livestock reduce output and therefore reduce supply.
5. Government policies - taxes, subsidies and price control affect farmers' returns; subsidies increase supply while heavy taxation reduces it.

Détails de la réponse

(a) Six relationships between agriculture and industries

• Agriculture supplies raw materials (cotton, cocoa, rubber, oil palm) to industries.
• Industries supply farm inputs (fertilizers, machinery, chemicals) to agriculture.
• Agriculture provides food for industrial workers.
• Agriculture provides a market for industrial goods.
• Industries process and add value to agricultural produce.
• Both provide employment and generate income and foreign exchange for the nation.

(b) Six factors affecting the success of commercial agriculture in Nigeria

• Capital: availability of adequate funds and credit to finance large-scale production.
• Land: access to large expanse of fertile land under a favourable land tenure system.
• Labour: availability of skilled and unskilled labour at a reasonable cost.
• Infrastructure: good roads, storage, processing and transport facilities.
• Marketing and price stability: reliable markets and stable prices for produce.
• Government policy: favourable agricultural policies, subsidies and political stability.
• (Also: climate/weather and availability of improved technology.)

(c) Eight agricultural research institutes in Nigeria

1. International Institute of Tropical Agriculture (IITA), Ibadan.
2. Cocoa Research Institute of Nigeria (CRIN), Ibadan.
3. National Cereals Research Institute (NCRI), Badeggi.
4. National Root Crops Research Institute (NRCRI), Umudike.
5. Nigerian Institute for Oil Palm Research (NIFOR), Benin.
6. National Animal Production Research Institute (NAPRI), Zaria.
7. Institute for Agricultural Research (IAR), Zaria.
8. Rubber Research Institute of Nigeria (RRIN), Benin.
9. (Also: NIHORT Ibadan, NVRI Vom, NIFFR New Bussa.)

Détails de la réponse

Cultivation of maize

(a) Land preparation

The land is cleared of bush, stumped, ploughed and harrowed to produce a fine, loose seedbed. Ridges or beds may be made where necessary for good drainage.

(b) Propagation

Maize is propagated sexually by seeds (grains). Healthy, viable and certified/improved seeds are used.

(c) Planting date

Maize is planted at the onset of the rains, usually March to April for the early season and August to September for the late season in the forest zone.

(d) Seed rate

About 20 to 25 kg of seed per hectare, sowing two to three seeds per hole and later thinning to one or two plants.

(e) Spacing

A spacing of about 90 cm between rows and 25 to 30 cm within rows (about 90 cm by 25 cm), giving roughly 40,000 to 50,000 plants per hectare.

(f) Fertilizer requirement

Maize is a heavy feeder. Apply a compound fertilizer such as N.P.K. at planting or two to three weeks after planting, followed by a top dressing of a nitrogenous fertilizer (e.g. urea or sulphate of ammonia) about five to six weeks after planting.

(g) Weeding

The farm is kept weed-free by hoeing or by the use of herbicides. Two to three weedings are usually done, with the first about two to three weeks after planting.

(h) Harvesting

Maize is harvested green (fresh) for boiling or roasting about two to three months after planting, or left to dry on the plant and harvested as dry grain after about three to four months.

(i) Storage

The grains are properly dried to a safe moisture content and stored in cribs, silos, jute bags or rhombus. They may be shelled and treated with approved chemicals to protect against weevils, rats and moulds.

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(a) Four common survey equipment/tools and their uses

• Ranging pole: used for marking out and sighting straight lines during survey.
• Measuring/surveyor tape (or chain): used for measuring horizontal distances between points.
• Prismatic compass: used for measuring the bearing (direction) of survey lines.
• Levelling instrument (dumpy level) and staff: used for determining differences in height/elevation of points on the land.
• (Others acceptable: theodolite for measuring horizontal and vertical angles; arrows/pegs for marking points.)

(b) Importance of farm surveying and planning

• It gives the exact size, shape and boundaries of the farmland.
• It helps to prepare a map/plan of the farm for proper record and reference.
• It guides the proper layout and location of farm structures, roads and drainage.
• It helps to allocate land to different enterprises efficiently.
• It helps to determine the level and slope of the land for irrigation and erosion control.
• It helps to settle boundary disputes and provides evidence of ownership.
• It aids proper planning, budgeting and estimation of inputs for the farm.

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(a) Six reasons why farm accounts should be kept

• To know whether the farm is making a profit or a loss.
• To serve as a guide for planning and future decision making.
• To help in securing loans and credit from banks and other lenders.
• To provide a basis for assessing tax.
• To keep records of assets, liabilities, income and expenditure of the farm.
• To measure the efficiency of the farm and compare performance from year to year.

(b) Profit and Loss Account for Ada Farms for the year ending December, 1993

Expenditure

Income

Net profit \[ = \text{Total income} - \text{Total expenditure} = 74{,}000 - 66{,}600 = N7{,}400.00 \]

Since income exceeds expenditure, Ada Farms made a net profit of N7,400.00 for the year. (Produce consumed at home and the opening/closing valuations are included because they form part of the farm income and expenditure.)

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(a) Soil pH

Soil pH is a measure of the degree of acidity or alkalinity of the soil, expressed on a scale of 0 to 14. A pH of 7 is neutral, values below 7 are acidic, and values above 7 are alkaline. Most crops grow best in slightly acidic to neutral soils (about pH 6 to 7). Acidity can be corrected by liming, while alkalinity may be reduced by adding sulphur or organic matter. Soil pH affects the availability of nutrients and the activity of soil organisms.

(b) Soil texture

Soil texture refers to the relative proportion of the different sizes of mineral particles (sand, silt and clay) in a soil. It determines whether a soil is sandy, loamy or clayey. Texture influences water-holding capacity, drainage, aeration and nutrient retention. Loamy soil, which is a balanced mixture of sand, silt and clay, is the best for most crops.

(c) Soil organisms

Soil organisms are the living things found in the soil. They include micro-organisms such as bacteria, fungi and algae, and macro-organisms such as earthworms, termites, millipedes and rodents. They help to decompose organic matter into humus, release and recycle nutrients, fix nitrogen, and improve soil structure and aeration. A few of them are harmful as pests or disease-causing organisms.

(d) Soil profile

A soil profile is the vertical section of the soil from the surface down to the parent rock, showing the different layers called horizons. The main horizons are the top soil (A horizon), the sub soil (B horizon), the weathered parent material (C horizon) and the underlying bed rock (D or R horizon). It is studied to know the depth, fertility and suitability of a soil for crop production.

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(a)(i) Four advantages of the deep litter system

• Birds move about freely and take exercise, keeping them healthy.
• Cost of construction and equipment is relatively low.
• The litter builds up manure that can be used on the farm.
• Birds obtain some vitamin B12 and warmth from the built-up litter.

(a)(ii) Four disadvantages of the deep litter system

• Diseases and parasites spread easily because birds are in contact with droppings.
• It is difficult to detect and cull individual sick or non-laying birds.
• Damp litter releases ammonia and encourages disease.
• Eggs laid on the floor may be dirty, broken or eaten by the birds; cannibalism may occur.

(b) One disadvantage of using saw-dust as litter

Saw-dust is dusty and can be eaten by the birds or cause respiratory problems; it also cakes and becomes damp easily, encouraging disease.

(c) Calculation

Floor area of the house \[ = 10\,\text{m} \times 50\,\text{m} = 500\,\text{m}^2 \]

At 3 adult fowls per square metre, number of fowls \[ = 500\,\text{m}^2 \times 3 = 1500 \text{ adult fowls}. \]

(d) Three other methods of keeping poultry

1. Battery cage system.
2. Free range (extensive) system.
3. Fold (ark/semi-intensive) system.

Détails de la réponse

(a) Balanced ration

A balanced ration is the feed given to a farm animal within a 24-hour period that contains all the essential nutrients (carbohydrates, proteins, fats, minerals, vitamins and water) in the right proportion required for maintenance, growth, reproduction and production.

(b) Stages in the preparation of the feed ingredients

(i) Bone meal

• Bones are collected and boiled to soften them and remove flesh and fat.
• The bones are dried, then crushed, ground or milled into powder.
• The powder is sieved and bagged for use.

(ii) Blood meal

• Fresh blood is collected from the slaughter house.
• It is boiled/cooked or steamed to coagulate it and remove excess water.
• The coagulated blood is drained, dried, then ground into powder, sieved and bagged.

(iii) Fish meal

• Waste or trash fish is collected and cooked/steamed.
• The oil and water are pressed out and the residue is dried.
• The dried fish is ground into powder, sieved and bagged.

(iv) Cotton seed meal

• Cotton seeds are collected and the lint and hulls (seed coats) are removed.
• The kernels are heated and the oil is extracted (pressed out).
• The remaining cake is dried, ground into meal, sieved and bagged.

Détails de la réponse

(a) Black pod of cocoa

• Causal organism: a fungus, Phytophthora palmivora (also Phytophthora megakarya).
• Symptoms: brown to black spots appear on the pod, spread rapidly to cover the whole pod, which turns black, rots, hardens and mummifies; the beans inside are destroyed.
• Spread: favoured by high humidity and rainfall; spread by rain splash, wind, insects and contact.
• Control: regular removal and destruction of infected pods (sanitation); frequent spraying with copper-based fungicides (e.g. Bordeaux mixture); prune to reduce humidity; ensure good drainage and adequate spacing; plant resistant varieties.

(b) Leaf blight of cassava

• Causal organism: a bacterium, Xanthomonas campestris pv. manihotis (cassava bacterial blight); (fungal leaf spots such as Cercospora also cause blighting).
• Symptoms: angular brown/water-soaked spots on the leaves, blighting and wilting of leaves, defoliation, die-back of shoots and gum exudation on stems in the bacterial type; severe attack reduces tuber yield.
• Spread: spread through infected cuttings, rain splash, wind and farm tools.
• Control: use clean, disease-free (resistant) cuttings; practise crop rotation and field sanitation; remove and burn infected plants; avoid overhead injury and disinfect tools; apply appropriate chemicals where necessary.

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(a) The water cycle (hydrological cycle)

The water cycle is the continuous circulation of water between the earth surface and the atmosphere. The annotated diagram should show the following labelled stages arranged in a cycle:

• Evaporation: heat from the sun turns water from seas, rivers and lakes into water vapour that rises into the atmosphere.
• Transpiration: plants give out water vapour from their leaves into the atmosphere.
• Condensation: the rising water vapour cools and condenses to form clouds.
• Precipitation: the condensed water falls back to the earth as rain, hail or dew.
• Run-off and infiltration: some water flows over the surface into rivers and seas, while some sinks into the soil to become ground water, and the cycle repeats.

(b) Three forms in which water exists in the soil

1. Gravitational water (free water that drains away by gravity).
2. Capillary water (held around soil particles and available to plants).
3. Hygroscopic water (tightly held as a thin film on soil particles, not available to plants).

(c) Five importance of water to crops

• It is needed for seed germination.
• It is a raw material for photosynthesis.
• It dissolves soil nutrients and aids their absorption and transport within the plant.
• It keeps plant cells turgid, maintaining the shape and firmness of the plant.
• It cools the plant through transpiration and regulates temperature.