gce model questions vol1 2022 agricultural_science | Essay

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Question 1 View Details
A smallholder farm in the northern region practices continuous cultivation of maize on the same field year after year.
Question Parts
(a)
Explain how continuous monoculture of maize can affect the biodiversity of the farm ecosystem.
(b)
Discuss two agronomic practices that could be introduced to mitigate the negative ecological impacts identified in part (a).
(c)
Evaluate how the adoption of the practices in part (b) could influence the long‑term productivity of the farm.
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Question 2 View Details
A student determines the field capacity of a loamy soil using the laboratory apparatus shown in the illustration.
Question Parts
(a)
Outline the step‑by‑step procedure for measuring field capacity with this setup.
(b)
Using the data recorded in the diagram (dry soil mass = 500 g, wet soil mass after drainage = 620 g, water retained = 120 ml, cylinder diameter = 5 cm, soil height = 20 cm), calculate:
(c)
Briefly discuss how the obtained field capacity value would influence irrigation scheduling for a cereal crop grown on this soil.
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Question 3 View Details
Explain the role of nitrogen in plant growth and describe the main processes of the nitrogen cycle that are relevant to crop production.
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Question 4 View Details
A smallholder farmer plans to introduce a crop‑rotation system on a 2‑hectare farm.
Question Parts
(a)
List three agronomic benefits of crop rotation.
(b)
Suggest a three‑year rotation sequence suitable for the humid tropical zone and justify your choice.
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Question 5 View Details
A farmer has 5 hectares of land and plans to adopt a two‑year crop rotation of maize (Zea mays) and soybeans (Glycine max). The following information is available: - Expected average yield of maize = 4.5 t ha⁻¹; market price = ₦150 000 t⁻¹. - Expected average yield of soybeans = 2.8 t ha⁻¹; market price = ₦120 000 t⁻¹. - Maize requires 150 kg of nitrogen (N) per tonne of grain produced. - Soybeans fix 45 kg N per tonne of grain and return 30 kg N ha⁻¹ to the soil as residue after harvest. - Synthetic N‑fertiliser (urea) costs ₦55 000 per tonne (46 % N by weight). - The farmer will apply fertiliser only to the maize crop and will rely on the residual N from the preceding soybean crop. - Fixed production costs (land preparation, planting, pest control) are ₦25 000 ha⁻¹ each year, irrespective of the crop. Using this information, answer the following:
Question Parts
(a)
Calculate the gross income (revenue before costs) from each crop in its respective year.
(b)
Determine the amount of synthetic N‑fertiliser (in kg) that must be applied to the maize crop in Year 1, taking into account the residual N supplied by the preceding soybean crop.
(c)
Calculate the net profit for each year (gross income – fertiliser cost – fixed production cost). State whether the two‑year rotation is more profitable than growing maize continuously for both years (assume the same fertiliser requirement each year for continuous maize).
(d)
Suggest one agronomic practice that could improve the profitability of the maize‑soybean rotation and briefly justify its effect.
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Question 6 View Details
A smallholder in northern Nigeria rears West African dwarf goats. The following data pertain to a typical breeding female: - Desired market weight = 30 kg live weight. - Average daily gain (ADG) = 45 g day⁻¹. - Daily dry matter intake (DMI) = 3 % of body weight. - The concentrate feed used contains 18 % crude protein (CP) and 12 MJ kg⁻¹ metabolizable energy (ME). - The cost of the concentrate is ₦250 kg⁻¹. - Live‑weight market price = ₦1 200 kg⁻¹. - Fixed overheads (housing, water, veterinary) = ₦15 000 per animal per production cycle. Using the information above, answer the following questions:
Question Parts
(a)
Calculate the total number of days required for a kid to reach the desired market weight.
(b)
Determine the total amount (kg) of concentrate feed required for the whole growth period, assuming the concentrate supplies the entire dry‑matter intake.
(c)
Compute the total feed cost, the gross revenue, and the net profit per animal for the production cycle.
(d)
Discuss how improving the crude‑protein level of the concentrate from 18 % to 22 % could affect the profitability of the operation. Include in your answer the likely impact on growth rate, feed intake and overall cost.
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Question 7 View Details
A farmer cultivates 5 hectares of maize. The average potential yield is 4 tonnes per hectare and the market price is ₦200 per kilogram. During the growing season the farmer observes an outbreak of the fall armyworm (Spodoptera frugiperda). If the pest is left uncontrolled, a 30 % reduction in yield is expected. The farmer is considering two control options: • Chemical control using a synthetic insecticide. The cost of the insecticide is ₦12 000 per hectare and the cost of application is ₦3 000 per hectare. The insecticide is reported to give a 90 % reduction in the damage caused by the armyworm. • Biological control using a Bacillus thuringiensis (Bt) formulation. The cost of the Bt product is ₦8 000 per hectare. The Bt formulation gives an 80 % reduction in damage. Using this information, answer the following:
Question Parts
(a)
Calculate the monetary value of the expected loss per hectare if no control measures are taken.
(b)
Determine the net monetary benefit (loss avoided minus control cost) per hectare if the chemical control option is used.
(c)
Determine the net monetary benefit per hectare if the biological control (Bt) option is used.
(d)
Based on the calculations above, recommend the most economically justified control method and briefly discuss any two non‑economic factors that a farmer should also consider when choosing a control strategy.
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Question 8 View Details
During a rainy season a farmer notices that his tomato plants are wilting, the lower leaves are turning yellow and the vascular tissue of the stems shows brown discoloration. Laboratory analysis confirms the presence of the bacterium Ralstonia solanacearum. The disease is bacterial wilt. The farmer's farm has a potential yield of 30 tonnes per hectare and the market price of tomatoes is ₦150 per kilogram. If no control measures are applied, the disease can cause up to a 45 % loss in yield. The farmer is considering three management options: 1. Planting a resistant tomato variety – seed cost ₦5 000 per hectare. 2. Practising a one‑year crop rotation with a non‑host legume – additional labour cost ₦2 000 per hectare. 3. Applying a copper‑based bactericide – product cost ₦10 000 per hectare plus application cost ₦2 000 per hectare. The reported effectiveness of each option in reducing yield loss is: • Resistant variety – reduces loss to 15 % of the potential yield. • Crop rotation – reduces loss to 30 % of the potential yield. • Copper bactericide – reduces loss to 20 % of the potential yield. Answer the following questions:
Question Parts
(a)
Identify the disease and name its causal organism.
(b)
Briefly describe the disease cycle of bacterial wilt in tomatoes, highlighting the main sources of inoculum and the primary means of spread.
(c)
Calculate the expected monetary loss per hectare if the disease is left uncontrolled.
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Question 9 View Details
A commercial broiler farm in Oyo State has recently experienced an outbreak of disease among its birds. Over a period of two weeks, 1,200 out of a total of 8,000 birds died. The surviving birds show the following clinical signs: sudden onset of respiratory distress, swollen wattles, and white patches on the comb. Post‑mortem examination of five dead birds revealed frothy exudate in the trachea and petechial haemorrhages on the liver. The farm manager reports that the birds were vaccinated against Newcastle disease but not against any other disease. Laboratory tests on pooled tissue samples have detected a virus belonging to the family *Paramyxoviridae* but the specific strain has not been identified.
Question Parts
(a)
Identify the most likely disease causing the outbreak and justify your choice using the clinical and post‑mortem findings.
(b)
Suggest two laboratory diagnostic tests that would confirm the specific viral strain involved.
(c)
Outline an integrated disease control programme for the farm, covering immediate, medium‑term and long‑term measures.
(d)
Estimate the direct economic loss incurred so far, assuming a market price of ₦1,200 per live bird and a salvage value of ₦300 per dead bird.
(e)
Discuss any zoonotic risk associated with the disease and the implications for public health.
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Question 10 View Details
A mixed farm in Kaduna State occupies 120 hectares, of which 70 ha are used for crop production (maize and soybean) and 50 ha for livestock (cattle and goats). The farmer plans a five‑year expansion and wishes to prepare a comprehensive farm business plan. The following data are available:
Question Parts
(a)
Using the data below, calculate the projected gross income for each of the five years. Assume the following annual changes: maize yield increases by 5 % per year, soybean yield by 3 % per year, cattle milk production per head rises by 2 % per year, and goat meat production per head rises by 1 % per year. Prices are assumed constant over the period. - Maize: current yield 3.5 t ha⁻¹, price ₦120 000 t⁻¹, cultivated area 40 ha. - Soybean: current yield 2.0 t ha⁻¹, price ₦180 000 t⁻¹, cultivated area 30 ha. - Cattle: 120 heads, average milk yield 15 L day⁻¹ per head, 300 days per year, price ₦150 per litre. - Goats: 200 heads, average carcass weight 20 kg per head, price ₦2 500 kg⁻¹.
(b)
Estimate the total variable cost for each year, given the following unit costs (assumed constant): - Maize seed: ₦15 000 ha⁻¹ - Soybean seed: ₦12 000 ha⁻¹ - Fertiliser (NPK) for crops: ₦30 000 ha⁻¹ - Cattle feed: ₦2 000 per head per year - Goat feed: ₦1 200 per head per year. Include only the listed variable costs in your calculation.
(c)
Using the figures from (a) and (b), compute the net profit for each of the five years and identify the year in which the farm first achieves a net profit margin of at least 20 %.
(d)
Provide three management recommendations that would improve the farm’s financial sustainability over the five‑year period, considering both agronomic and livestock aspects.
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