waec model questions vol1 2023 agricultural_science | Practical

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Question 1 View Details
A farmer wishes to evaluate the insect biodiversity in a 2 ha field using the sweep‑net method. Over five consecutive days (Monday to Friday) the farmer performed three 10‑minute sweeps each day and recorded the numbers of insects captured in three functional groups: herbivores, predators and pollinators. The data obtained are shown in the table below. | Day | Herbivores | Predators | Pollinators | |-----|------------|-----------|-------------| | Mon | 30 | 12 | 8 | | Tue | 25 | 15 | 10 | | Wed | 28 | 10 | 12 | | Thu | 32 | 14 | 9 | | Fri | 27 | 13 | 11 | Using this information, answer the following:
Question Parts
(a)
Calculate the average number of insects per day for each functional group.
(b)
State which functional group was the most abundant over the five‑day period.
(c)
Determine the percentage that predators contributed to the total number of insects captured.
(d)
Identify two possible sources of error inherent in the sweep‑net method used.
(e)
Suggest one management practice that could be adopted to enhance the pollinator population in the field.
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Question 2 View Details
A soil scientist is determining the nitrate (NO₃⁻) and phosphate (PO₄³⁻) contents of a field soil intended for maize production. A 50 g air‑dried soil sample is extracted with 250 mL of distilled water. The extract is filtered and its absorbance is measured with a calibrated spectrophotometer. - Absorbance for nitrate = 0.45 (λ = 220 nm) - Absorbance for phosphate = 0.30 (λ = 880 nm) The calibration equations supplied by the laboratory are: - Nitrate: Concentration (mg L⁻¹) = 20 × Absorbance - Phosphate: Concentration (mg L⁻¹) = 15 × Absorbance Using the data above, answer the following questions:
Question Parts
(a)
Calculate the concentration of nitrate and phosphate in the soil sample expressed as mg kg⁻¹.
(b)
Determine the soil N : P ratio on a mg kg⁻¹ basis.
(c)
Given that the recommended N : P ratio for optimum maize growth is 3 : 1, state which nutrient is limiting in this soil and justify your answer.
(d)
List two agronomic measures that could be adopted to correct the identified nutrient limitation.
(e)
Identify one possible source of error in the analytical procedure and suggest a way to minimise it.
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Question 3 View Details
A farmer wishes to clear a 0.5‑hectare plot of weeds using three hand tools: a hoe, a cutlass and a garden fork. Under identical field conditions he records the following data for each tool: - Time taken to clear the 0.5 ha: Hoe – 4.5 h, Cutlass – 3.2 h, Fork – 5.0 h. - Average force applied per stroke: Hoe – 30 N, Cutlass – 45 N, Fork – 25 N. - Stroke length: Hoe – 0.40 m, Cutlass – 0.60 m, Fork – 0.35 m. - Strokes made per minute: 150 strokes/min for each tool. Using this information, answer the following: a) Calculate the total mechanical work (in kilojoules) performed by each tool in one hour of operation. b) Determine which tool is the most energy‑efficient for clearing the field, expressed as work (kJ) required per square metre cleared. c) Based on the efficiency results and the ergonomics of the forces involved, recommend the most suitable tool for the farmer and justify your choice.
Question Parts
(a)
Calculate the total mechanical work (in kilojoules) performed by each tool in one hour of operation.
(b)
Determine which tool is the most energy‑efficient for clearing the field, expressed as work (kJ) required per square metre cleared.
(c)
Based on the efficiency results and the ergonomics of the forces involved, recommend the most suitable tool for the farmer and justify your choice.
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Question 4 View Details
A small diesel‑powered tractor is used for ploughing. The engine is rated at 15 kW at 2000 rpm and consumes 3.5 L of diesel per hour at full load. The tractor pulls a single‑blade plough whose draft force varies linearly from 1200 N at the start of a furrow to 1800 N at the end of the furrow. Each furrow is 30 m long and the operator records a travel time of 2.5 minutes per furrow. Answer the following: a) Determine the average mechanical power (in kW) required to pull the plough over one furrow. b) Calculate the percentage of the engine’s rated power that is actually utilized during ploughing. c) Using the fuel consumption data, compute the specific fuel consumption (SFC) in kg kW⁻¹ h⁻¹, assuming diesel density of 0.85 kg L⁻¹. d) Identify two probable sources of inefficiency in the tractor‑plough system and suggest practical measures to improve overall performance.
Question Parts
(a)
Determine the average mechanical power (in kW) required to pull the plough over one furrow.
(b)
Calculate the percentage of the engine’s rated power that is actually utilized during ploughing.
(c)
Using the fuel consumption data, compute the specific fuel consumption (SFC) in kg kW⁻¹ h⁻¹, assuming diesel density of 0.85 kg L⁻¹.
(d)
Identify two probable sources of inefficiency in the tractor‑plough system and suggest practical measures to improve overall performance.
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