waec model questions vol1 2020 agricultural_science | Practical

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Question 1 View Details
A researcher wants to investigate how different shade intensities affect the soil temperature in a maize field. Three identical 5 m × 5 m plots are each covered with a shade net that reduces sunlight by 30 %, 50 % and 70 % respectively. An uncovered plot will serve as the control. Soil temperature at a depth of 10 cm is to be recorded with a mercury thermometer at 09:00 h for five consecutive days.
Question Parts
(a)
State a complete step‑by‑step procedure for setting up the experiment and for recording the temperature data. Include how you would organise the data in a table.
(b)
The following temperatures (°C) were obtained: | Day | Control | 30 % shade | 50 % shade | 70 % shade | |-----|---------|-----------|-----------|-----------| | 1 | 28.4 | 26.9 | 25.5 | 24.2 | | 2 | 27.8 | 26.5 | 25.1 | 23.9 | | 3 | 28.1 | 26.7 | 25.3 | 24.0 | | 4 | 27.5 | 26.2 | 24.9 | 23.7 | | 5 | 28.0 | 26.8 | 25.4 | 24.1 | Calculate the mean temperature for each plot, identify which shade level gives the lowest average temperature, and determine the percentage reduction in mean temperature of that plot relative to the control.
(c)
Mention two possible sources of error in this experiment and suggest one way to minimise each.
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Question 2 View Details
A soil scientist is evaluating the lime requirement for an acidic loamy soil in a wheat field. The target pH for optimal wheat growth is 6.5. The current soil pH measured with a calibrated pH meter is 5.2. The soil's buffer capacity, determined by a laboratory titration, is 2.5 meq · 100 g⁻¹. The bulk density of the soil is 1.3 g cm⁻³ and the plough layer depth is 15 cm.
Question Parts
(a)
Outline the practical steps for collecting a representative soil sample from the field and preparing it for pH measurement with a digital pH meter.
(b)
Using the data provided, calculate the amount of agricultural lime (CaCO₃) required per hectare to raise the soil pH from 5.2 to 6.5. Assume the relationship: Lime requirement (kg ha⁻¹) = [(Target pH – Current pH) × 1000] ÷ Buffer capacity (meq · 100 g⁻¹) × Soil weight per hectare (kg). Soil weight per hectare = bulk density × plough depth × 10,000 m² × 1,000 kg m⁻³.
(c)
Explain two agronomic implications of applying the calculated amount of lime to the field.
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Question 3 View Details
A farmer intends to use a hand hoe to prepare a garden plot that measures 30 m in length and 12 m in width. The hand hoe has a blade length of 0.45 m and an effective cutting width of 0.12 m. The farmer makes a forward pass along the length of the plot, then turns and makes a second pass parallel to the first, continuing until the whole plot is tilled.
Question Parts
(a)
Calculate the area of soil turned in one forward pass of the hoe.
(b)
Estimate the total number of forward passes required to till the whole plot, assuming no overlap and that the farmer works systematically from one edge to the other.
(c)
Identify two possible sources of error that could cause the actual number of passes to differ from the calculated estimate, and suggest a practical way to minimise each error.
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Question 4 View Details
A smallholder farmer uses a 25‑horsepower (hp) diesel‑engine tractor to cultivate a 5‑hectare field. The tractor’s fuel‑consumption chart is given below: Load (% of rated power) | Fuel consumption (L h⁻¹) --------------------------|-------------------------- 50 | 2.5 70 | 3.2 90 | 4.1 During field cultivation the tractor operates at an average load of 65 % of its rated power and moves at an average field speed of 4 km h⁻¹. The cultivator attached to the tractor has a working width of 2.5 m. Answer the following:
Question Parts
(a)
Using linear interpolation, estimate the tractor’s fuel consumption at 65 % load.
(b)
Calculate the total time required to cultivate the 5‑hectare field at the given speed, assuming the tractor works continuously without turning time.
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