waec model questions vol1 2018 agricultural_science | Essay

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Question 1 View Details
A farmer practices mixed cropping on a 5‑hectare farm located in a tropical savanna zone where the mean annual rainfall is 1200 mm, evenly distributed. The farmer rotates maize, cowpea and groundnut in a three‑year cycle. The soil is a Ferric Acrisol with low organic matter.
Question Parts
(a)
Explain how the three‑year rotation of maize, cowpea and groundnut contributes to soil fertility and pest management.
(b)
The farmer wishes to increase the soil organic carbon (SOC) by 0.5 t C ha⁻¹ per year. Assuming the bulk density of the soil is 1.3 g cm⁻³ and the depth of incorporation is 15 cm, calculate the amount of dry crop residue that must be added each year, given that the residue contains 40 % carbon.
(c)
Discuss two ecological advantages of maintaining a hedgerow of native trees along the field boundary.
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Question 2 View Details
The illustration shows a laboratory pressure‑plate apparatus used to determine the field capacity (FC) and permanent wilting point (PWP) of a soil sample by applying different matric potentials.
Question Parts
(a)
Explain the principle by which the pressure‑plate apparatus determines field capacity and permanent wilting point.
(b)
In the experiment, 200 g of oven‑dry soil is placed in the holder. At a pressure of 0.33 bar the water retained after drainage is measured as 80 g. At a pressure of 15 bar the water retained is 30 g. Calculate the field capacity and the permanent wilting point of the soil, expressed as % gravimetric water content.
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Question 3 View Details
A farmer intends to improve the fertility of his field by applying inorganic fertilizers.
Question Parts
(a)
Explain the functions of the three major plant nutrients: nitrogen (N), phosphorus (P), and potassium (K).
(b)
The farmer applies 150 kg N ha⁻¹, 80 kg P₂O₅ ha⁻¹ and 60 kg K₂O ha⁻¹. Convert the amounts of P₂O₅ and K₂O to elemental phosphorus (P) and potassium (K) using the factors P = 0.44 P₂O₅ and K = 0.83 K₂O, and state the total kilograms of N, P and K supplied per hectare.
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Question 4 View Details
A smallholder wishes to expand his cassava production through vegetative propagation.
Question Parts
(a)
Distinguish between sexual and asexual propagation of crops.
(b)
Each 30 cm cassava stem cutting yields 2.5 new plants. If the farmer has 120 cuttings, how many plants will be obtained?
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Question 5 View Details
A farmer intends to cultivate maize and cowpea on a 2‑hectare field using a land‑use ratio of 3:1 (maize : cowpea). The recommended seed rates are 25 kg ha⁻¹ for maize and 10 kg ha⁻¹ for cowpea. For fertiliser, the farmer applies 120 kg N ha⁻¹ to maize (as urea, 46 % N) and 20 kg P₂O₅ ha⁻¹ to cowpea (as single superphosphate, 20 % P₂O₅). The farmer has a total budget of ₦150 000. Current input costs are: maize seed ₦120 kg⁻¹, cowpea seed ₦80 kg⁻¹, urea ₦45 kg⁻¹, single superphosphate ₦55 kg⁻¹.
Question Parts
(a)
Determine the area (in hectares) allocated to maize and to cowpea.
(b)
Calculate the total quantity of each input (seed, urea, superphosphate) required for the whole field.
(c)
Compute the total cost of all inputs.
(d)
Is the farmer’s budget of ₦150 000 sufficient? If not, suggest one input that could be reduced by 10 % to bring the total cost within the budget and state the new total cost.
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Question 6 View Details
A smallholder keeps 10 lactating cows. Each cow yields an average of 12 L of milk per day. The desired milk composition is 3.5 % fat. Two feedstuffs are available: - Concentrate: 30 % crude protein (CP), 10 % fat, cost ₦250 kg⁻¹. - Roughage (dry matter): 12 % CP, 2 % fat, cost ₦120 kg⁻¹. Nutrient requirements per cow per day are 1.2 kg CP and 0.4 kg fat. Milk is sold at ₦150 per litre.
Question Parts
(a)
Determine the minimum kilograms of concentrate and roughage required per cow per day, assuming the concentrate supplies all the required CP and fat and the roughage supplies the remaining dry‑matter needed to meet the cow’s total nutrient intake.
(b)
Calculate the total daily feed cost for the whole herd based on the quantities found in part (a).
(c)
Compute the gross daily income from milk sales.
(d)
Determine the daily profit after deducting feed costs.
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Question 7 View Details
A soil profile in the northern region of Nigeria is described as follows: - Horizon A: dark brown, loamy texture, pH 5.5, organic matter 2.5%, base saturation 45%. - Horizon B: reddish‑brown, clay loam, pH 5.2, organic matter 1.2%, base saturation 30%. - Horizon C: pale yellow, sandy loam, pH 5.0, organic matter 0.8%. - The soil is well‑drained and shows slight signs of erosion. Based on this information:
Question Parts
(a)
Identify the soil order (FAO classification) to which this profile most likely belongs.
(b)
Discuss the suitability of this soil for the cultivation of rain‑fed rice, mentioning at least three soil‑related factors.
(c)
Recommend two soil amendments that would improve the fertility of this soil for rice production and explain the mode of action of each amendment.
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Question 8 View Details
A farmer intends to grow 5 ha of maize and expects a grain yield of 4 t ha⁻¹. The soil test shows available nitrogen (N) of 40 kg ha⁻¹, phosphorus (P) of 12 kg ha⁻¹ and potassium (K) of 80 kg ha⁻¹. The recommended nutrient requirements for the target yield are 150 kg N, 60 kg P₂O₅ and 120 kg K₂O per hectare. Using this information, calculate the fertilizer quantities needed for the whole farm and discuss the timing of fertilizer application for each nutrient.
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