waec model questions vol1 2023 agricultural_science | Essay

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Question 1 View Details
A smallholder farmer in the savanna zone wishes to improve the ecological sustainability of his 2‑hectare farm.
Question Parts
(a)
Explain how practising crop rotation can enhance soil fertility and reduce pest pressure.
(b)
Identify three ecological services that a mixed farming system (crops together with livestock) provides and briefly describe each.
(c)
The farmer decides to allocate 40 % of the land to legumes, 30 % to cereals and the remaining area to root crops. Calculate the area (in hectares) for each crop group and explain why this pattern supports sustainable agriculture.
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Question 2 View Details
A soil‑infiltration experiment is set up as shown in the illustration. A cylindrical soil column of height 30 cm and internal diameter 5 cm is placed vertically. A graduated cylinder (capacity 250 ml) is used to deliver water onto the top of the soil column. A stopwatch records the time taken for water to infiltrate the soil. In the trial recorded, 150 ml of water entered the soil column in 45 minutes.
Question Parts
(a)
List three variables that must be kept constant during the experiment and briefly justify why each should be controlled.
(b)
Calculate the infiltration rate in centimetres per hour (cm h⁻¹). Show all steps.
(c)
Based on the infiltration rate obtained, advise whether the soil is suitable for a rain‑fed crop and justify your recommendation using typical infiltration thresholds.
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Question 3 View Details
A soil sample from a farm has the following texture composition: sand 40%, silt 40% and clay 20%.
Question Parts
(a)
Classify the soil texture according to the USDA soil texture triangle.
(b)
Explain how this texture influences the soil’s water‑holding capacity and drainage.
(c)
Recommend one crop that would be suitable for this soil and justify your choice.
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Question 4 View Details
A soil test for a maize field shows the following nutrient deficiencies: nitrogen 30 kg/ha, phosphorus 20 kg/ha and potassium 15 kg/ha. The farmer intends to use urea (46% N) and diammonium phosphate (DAP) (18% N, 46% P₂O₅).
Question Parts
(a)
Calculate the amount of urea (in kg) required to supply the nitrogen deficiency after accounting for the nitrogen supplied by DAP.
(b)
Calculate the amount of DAP (in kg) needed to meet the phosphorus deficiency (note: 1 kg P₂O₅ = 0.44 kg P).
(c)
State one agronomic practice that can improve the efficiency of the applied fertilizers.
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Question 5 View Details
A farmer has a 2‑hectare field that he intends to use for intercropping maize (Zea mays) and cowpea (Vigna unguiculata). He plans to allocate the area in a 3:1 ratio (maize : cowpea). The recommended seed rate is 25 kg ha⁻¹ for maize and 80 kg ha⁻¹ for cowpea. Expected yields are 4 t ha⁻¹ for maize and 1.2 t ha⁻¹ for cowpea. Market prices are ₦120 per kg for maize and ₦250 per kg for cowpea. Production costs (excluding seed) are ₦30 000 per hectare for maize and ₦20 000 per hectare for cowpea.
Question Parts
(a)
Calculate the amount of seed required for each crop (in kilograms).
(b)
Estimate the gross income from each crop and the total gross income from the intercropping system.
(c)
Discuss two agronomic advantages of intercropping maize with cowpea in this situation.
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Question 6 View Details
A smallholder keeps a milking herd of 8 Friesian cows. Each cow produces on average 12 L of milk per day. The farmer wishes to formulate a concentrate supplement that provides an additional 2 MJ of metabolizable energy (ME) per cow per day. The concentrate is to be prepared from maize grain (ME = 13 MJ kg⁻¹, CP = 9 %) and soybean meal (ME = 12 MJ kg⁻¹, CP = 44 %). The supplement must contain at least 20 % crude protein (CP). The cost of maize is ₦30 kg⁻¹ and soybean meal is ₦80 kg⁻¹.
Question Parts
(a)
Determine the proportion (by weight) of maize and soybean meal in the supplement that satisfies both the energy and the minimum protein requirements. Show all calculations.
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Question 7 View Details
A farmer in the North Central zone of Nigeria has been experiencing severe defoliation of his maize crop during the early rainy season. Field observations reveal the presence of a nocturnal, leaf‑feeding insect that creates ragged holes in the foliage and leaves behind frass. The farmer wishes to adopt an integrated approach to manage the pest while minimising environmental damage.
Question Parts
(a)
Identify the pest described and give its scientific name.
(b)
Outline the complete life cycle of the pest, indicating the duration of each stage under typical Nigerian conditions.
(c)
Propose an integrated pest‑management (IPM) programme for this pest. Include at least one cultural, one biological and one chemical control method, and briefly justify the choice of each.
(d)
The recommended chemical control is a synthetic insecticide formulated at 200 g L⁻¹. The label advises a spray volume of 0.5 L ha⁻¹. The farmer’s field measures 2 ha. Calculate the total volume of spray required and the amount of active ingredient (in grams) that will be applied to the whole field.
(e)
Discuss two possible adverse environmental effects of using the chemical control and suggest one management practice to mitigate each effect.
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Question 8 View Details
During a routine scouting of a 5‑ha maize field in the Middle Belt, a farmer observed leaf lesions that were elongated, grey‑green and surrounded by a yellow halo. A sample of 200 plants was examined, and 30 plants showed typical symptoms of the disease. Of the symptomatic plants, 10 exhibited mild lesions covering less than 25 % of the leaf area, while the remaining 20 showed severe lesions covering more than 50 % of the leaf area.
Question Parts
(a)
State the most likely disease and the causal pathogen.
(b)
Calculate the disease incidence (%) and the disease severity index (expressed as a percentage, rounded to one decimal place). Use a severity rating of 1 for mild lesions and 3 for severe lesions.
(c)
Recommend an integrated control strategy for this disease, mentioning at least one cultural, one chemical and one resistant‑variety measure, and justify each choice.
(d)
If the potential yield of the field is 5 t ha⁻¹ and each percent of disease incidence reduces yield by 0.8 % of the potential yield, estimate the expected yield loss (in kilograms per hectare) caused by the disease.
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