Practice neco model questions vol1 agricultural_science 2022 Past Questions

Question 1 View Details

A farmer harvests 10,000 kg of cassava roots with an initial moisture content of 70 % (wet basis). He uses a solar dryer in which the moisture content (M(t)) (as a fraction) decreases according to the differential equation $\frac{dM}{dt} = -k\bigl(M-M_a\bigr)$ where the ambient moisture (M_a = 0.05) and the constant (k = 0.03\,\text{h}^{-1}\). He wishes to dry the roots to a final moisture content of 20 % (wet basis).\n(a) Calculate the drying time required (in hours) to reach the target moisture.\n(b) Determine the total weight of the roots after drying.\n(c) If during storage the dried roots lose 2 % of their dry matter each month, find the net total weight after three months of storage (assume moisture remains at 20 %).

A. Drying time ≈ 45 h; weight after drying = 3,800 kg; weight after 3 months = 3,500 kg

B. Drying time ≈ 48.9 h; weight after drying = 3,700 kg; weight after 3 months = 3,450 kg

C. Drying time ≈ 52 h; weight after drying = 3,600 kg; weight after 3 months = 3,400 kg

Correct D. Drying time ≈ 48.9 h; weight after drying = 3,750 kg; weight after 3 months = 3,525 kg

Correct Answer: D

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Question 2 View Details

A 2‑ha maize field is being surveyed for stem borer damage. The economic threshold is 5 % of plants showing symptoms. From a random sample of 200 plants, 12 are damaged.\n(i) State whether chemical control is justified.\n(ii) If control is justified, the recommended spray rate is 1.5 L ha⁻¹ of a formulation containing 250 g a.i. L⁻¹. Because of reported resistance, the farmer must apply a mixture of pesticide A and pesticide B in the volume ratio 3:2, while keeping the total volume at the recommended rate. Calculate the volume of each pesticide to be applied per hectare.

A. Yes; apply 1.0 L of pesticide A and 0.5 L of pesticide B per hectare

B. No; chemical control is not justified

C. Yes; apply 0.75 L of pesticide A and 0.75 L of pesticide B per hectare

Correct D. Yes; apply 0.9 L of pesticide A and 0.6 L of pesticide B per hectare

Correct Answer: D

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Question 3 View Details

A rabbit farm raises 120 rabbits. Each rabbit gains an average of 150 g per week for 8 weeks. The feed offered contains 15 % crude protein. Rabbits require protein equal to 20 % of their live‑weight gain.\n(a) Calculate the total amount of feed needed for the whole batch over the 8‑week period.\n(b) Determine the feed conversion ratio (FCR) and comment on the efficiency if the recommended FCR for rabbits is 1.20.

A. Feed required = 192 kg; FCR ≈ 1.20 (matches the recommended efficiency)

B. Feed required = 200 kg; FCR ≈ 1.45 (considerably less efficient than the recommended 1.20)

C. Feed required = 180 kg; FCR ≈ 1.20 (as efficient as the recommended value)

Correct D. Feed required = 192 kg; FCR ≈ 1.33 (slightly less efficient than the recommended 1.20)

Correct Answer: D

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Question 4 View Details

A teak plantation covers 50 ha and is 10 years old. The mean standing volume is 80 m³ ha⁻¹ and the annual volume increment is 5 % of the current standing volume. The manager wishes to harvest a portion each year while keeping the stand sustainable (i.e., after harvest and subsequent growth the total standing volume remains unchanged).\n(i) Determine the maximum total volume (in m³) that can be harvested annually from the whole plantation.\n(ii) If 1 m³ of teak wood contains 0.9 t of carbon, calculate the amount of carbon sequestered each year by the sustainable harvest.

A. Maximum sustainable harvest ≈ 190.5 m³ yr⁻¹; carbon sequestered ≈ 180 t yr⁻¹

B. Maximum sustainable harvest ≈ 200 m³ yr⁻¹; carbon sequestered ≈ 180 t yr⁻¹

C. Maximum sustainable harvest ≈ 150 m³ yr⁻¹; carbon sequestered ≈ 135 t yr⁻¹

Correct D. Maximum sustainable harvest ≈ 190.5 m³ yr⁻¹; carbon sequestered ≈ 171.4 t yr⁻¹

Correct Answer: D

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Question 5 View Details

A farmer intends to plant maize on 3 ha. Soil analysis shows available nutrients of N = 40 kg ha⁻¹, P₂O₅ = 15 kg ha⁻¹ and K₂O = 30 kg ha⁻¹. The target nutrient levels for optimum yield are N = 120 kg ha⁻¹, P₂O₅ = 60 kg ha⁻¹ and K₂O = 80 kg ha⁻¹. Fertiliser options are: urea (46 % N) at ₦45,000 t⁻¹, single superphosphate (20 % P₂O₅) at ₦55,000 t⁻¹, and muriate of potash (60 % K₂O) at ₦50,000 t⁻¹.\n(i) Calculate the amount (kg) of each fertiliser required per hectare to meet the target nutrient levels.\n(ii) Compute the total cost of fertilisers for the whole 3‑ha area.

A. Per ha: 180 kg urea, 210 kg SSP, 85 kg KCl; total cost for 3 ha ≈ ₦71,400

Correct B. Per ha: 174 kg urea, 225 kg SSP, 83 kg KCl; total cost for 3 ha ≈ ₦73,115

C. Per ha: 165 kg urea, 220 kg SSP, 90 kg KCl; total cost for 3 ha ≈ ₦72,800

D. Per ha: 170 kg urea, 230 kg SSP, 80 kg KCl; total cost for 3 ha ≈ ₦74,250

Correct Answer: B

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Question 6 View Details

An infectious animal disease has a basic reproduction number $R_0 = 2.5$. A farmer can either (i) vaccinate 70 % of the herd with a vaccine that is 80 % effective, or (ii) impose movement restrictions that reduce the contact rate by 40 %. Assuming these measures act independently on disease transmission, which control option results in the lower effective reproduction number $R_e$?

Correct A. Vaccination

B. No control needed

C. Movement restrictions

D. Both options equally effective

Correct Answer: A

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Question 7 View Details

A certain crop pest causes a loss of $0.5$ kg of maize per hectare for each insect present. The market price of maize is $\$0.5$ per kilogram, and the cost of applying an insecticide is $\$30$ per hectare. Using the economic threshold formula $ET = \dfrac{C}{V \times D}$, where $C$ is the control cost per hectare, $V$ is the market price per kilogram, and $D$ is the loss in kilograms per insect, calculate the threshold number of insects per hectare above which control is justified.

A. 60

Correct B. 120

C. 200

D. 150

Correct Answer: B

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Question 8 View Details

The total cost of producing maize is given by $TC = 0.02Q^{2} + 1500$ (where $Q$ is output in tonnes). The market price follows the linear demand function $P = 500 - 0.1Q$. Determine the profit‑maximising output level $Q^{*}$ (in tonnes) and the corresponding maximum profit (in dollars).

A. Q* ≈ 2500 tonnes; maximum profit ≈ $600,000

B. Q* ≈ 1500 tonnes; maximum profit ≈ $400,000

C. Q* ≈ 1800 tonnes; maximum profit ≈ $450,000

Correct D. Q* ≈ 2083 tonnes; maximum profit ≈ $519,335

Correct Answer: D

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Question 9 View Details

An extension officer wishes to evaluate a new fertilizer that is expected to increase maize yield by $0.8$ t ha$^{-1}$. From previous trials the standard deviation of yield is $1.2$ t ha$^{-1}$. To detect this difference with a 5 % significance level (two‑sided) and 80 % power, what is the minimum number of farms required in each of the treatment and control groups? (Use the formula $n = 2\,(Z_{\alpha/2}+Z_{\beta})^{2}\sigma^{2}/\Delta^{2}$.)

Correct A. 36

B. 24

C. 45

D. 30

Correct Answer: A

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Question 10 View Details

A mixed farm has 10 ha of land to allocate between two crops. Crop A yields 3 t ha$^{-1}$ and sells for $\$200$ per tonne, with a variable cost of $\$150$ per hectare. Crop B yields 2 t ha$^{-1}$ and sells for $\$250$ per tonne, with a variable cost of $\$120$ per hectare. Fixed costs for the farm amount to $\$2000$. What is the minimum area (in hectares) that must be planted to Crop A in order to achieve an overall profit of at least $\$2000$?

Correct A. 3

B. 2

C. 5

D. 4

Correct Answer: A

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Question 11 View Details

A farmer intends to raise 50 chickens to a final weight of $2.2$ kg each. Each chick currently weighs $0.5$ kg. The feed conversion ratio (FCR) is $2.0$ kg feed per kg weight gain for the first kilogram of gain, and for each additional kilogram of gain the FCR improves by $0.2$ kg feed per kg gain (i.e., it decreases by $0.2$). How many kilograms of feed are required in total for all the chickens?

A. 150

B. 170

C. 180

Correct D. 163

Correct Answer: D

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Question 12 View Details

A farmer plans to sow maize on a $5$ ha field. The recommended seed rate is $25$ kg ha$^{-1}$ assuming 100 % germination. The seed batch has a germination rate of $85$ %. In addition, a handling loss of $5$ % is expected during sowing. What is the total amount of seed (in kilograms) the farmer must purchase for the whole field? Round your answer to the nearest kilogram.

A. 160

B. 140

C. 170

Correct D. 154

Correct Answer: D

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Question 13 View Details

A dairy cow produces $30$ L of milk on the first day of lactation. Each subsequent day's yield decreases by $2$ % of the previous day's yield. The lactation period lasts $180$ days. Estimate the total milk production over the entire lactation period, rounding to the nearest litre.

A. 1500

Correct B. 1460

C. 1550

D. 1450

Correct Answer: B

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Question 14 View Details

A wheat field of $10$ ha normally yields $3{,}000$ kg ha$^{-1}$. A fungal disease affects $40$% of the field and reduces the yield in the infected area by $15$%. The market price of wheat is ₦$150$ per kg. Fungicide costs ₦$12{,}000$ per ha and, when applied to the whole field, eliminates any yield loss. Should the farmer apply the fungicide to the entire field? Show the net profit with and without treatment and state the decision.

A. Yes, net profit ₦4,500,000 (higher than ₦4,350,000 without treatment)

Correct B. Yes, net profit ₦4,380,000 (higher than ₦4,230,000 without treatment)

C. No, net profit ₦4,350,000 (lower than ₦4,380,000 without treatment)

D. Yes, net profit ₦4,250,000 (higher than ₦4,100,000 without treatment)

Correct Answer: B

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Question 15 View Details

The soil pH of a field is $5.5$. To raise the pH to $6.5$, the recommendation is to apply $2.5$ tonnes of agricultural lime per hectare for each pH unit increase. How many tonnes of lime are required per hectare to reach the target pH?

Correct A. 2.5

B. 1.25

C. 3.0

D. 5.0

Correct Answer: A

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Question 16 View Details

A soil sample contains $45\%$ sand, $35\%$ silt and $20\%$ clay. Using the USDA soil‑texture triangle, identify the soil texture class.

A. sandy loam

B. silt loam

C. clay loam

Correct D. loam

Correct Answer: D

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Question 17 View Details

A 5‑ha field is affected by a fungal disease. The disease incidence is initially $12\%$ and causes a yield loss of ₦200 per hectare for each percent of incidence. A fungicide costing ₦150 per hectare reduces the incidence to $4\%$. Should the farmer apply the fungicide? State the economic decision.

A. Undecided

B. Unjustified

C. Not justified

Correct D. Justified

Correct Answer: D

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Question 18 View Details

A tractor engine delivers $45$ kW at $1500$ rpm. It drives a plough through a belt drive with a pulley ratio of 3 : 1 (engine pulley : plough pulley). Determine the torque transmitted to the plough shaft in newton‑metres (N·m).

A. 720

Correct B. 860

C. 1050

D. 950

Correct Answer: B

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Question 19 View Details

A fishery follows logistic growth with carrying capacity $K = 200{,}000$ tonnes and intrinsic growth rate $r = 0.4$ yr$^{-1}$. The current stock is $N_0 = 80{,}000$ tonnes.\n\n(a) What is the maximum constant annual harvest ($H_{\max}$) that can be sustained without causing stock collapse?\n\n(b) If the fishery wishes the stock to reach $120{,}000$ tonnes after 5 years, what constant annual harvest $H$ should be set (approximate to the nearest tonne)?

A. Maximum sustainable harvest = 22,000 tonnes per year; Harvest for target = 13,200 tonnes per year

B. Maximum sustainable harvest = 25,000 tonnes per year; Harvest for target = 9,000 tonnes per year

Correct C. Maximum sustainable harvest = 20,000 tonnes per year; Harvest for target = 11,850 tonnes per year

D. Maximum sustainable harvest = 18,000 tonnes per year; Harvest for target = 10,500 tonnes per year

Correct Answer: C

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Question 20 View Details

In a mixed farming ecosystem the following organisms are present: maize crop, grasshopper, rabbit, and hawk. Arrange them in order of increasing trophic level.

A. grasshopper, maize, rabbit, hawk

B. maize, rabbit, grasshopper, hawk

Correct C. maize, grasshopper, rabbit, hawk

D. maize, grasshopper, hawk, rabbit

Correct Answer: C

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Question 21 View Details

An agricultural extension programme plans to train 50 farmers. The programme has a fixed overhead cost of ₦150,000 and a variable cost of ₦20 per farmer trained. Each farmer's baseline yield is 2,000 kg and the market price is ₦120 per kg. Adoption of the new technology is expected to increase yield by $15\%$ for a farmer, but only $60\%$ of the trained farmers are expected to adopt it. The benefits from the increased yield are realised each year for three years after training. Using a discount rate of $10\%$ per annum, calculate the net present value (NPV) of the programme.

A. 2120000

B. 2034800

Correct C. 2534800

D. 2845600

Correct Answer: C

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Question 22 View Details

The adoption rate of a new farming practice is modelled by the function $A(N)=0.4+0.1\ln(N+1)$, where $N$ is the number of extension agents per 1,000 farmers and $A$ is the proportion of farmers adopting the practice (capped at 0.8). Each agent costs ₦500,000 per year. Determine the smallest integer value of $N$ that will achieve at least a 70\% adoption rate and compute the corresponding annual budget for the agents.

A. 20 agents; ₦12000000

B. 18 agents; ₦9000000

C. 22 agents; ₦11000000

Correct D. 20 agents; ₦10000000

Correct Answer: D

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Question 23 View Details

A grain store can be kept at any integer temperature between 5 °C and 25 °C. The monthly loss of grain due to respiration is modelled by $R(T)=200\,e^{-0.05T}$ kg, and the monthly loss due to insect infestation is $I(T)=\begin{cases}0,& T\le10\\150\bigl(1-e^{-0.1(T-10)}\bigr),& T>10\end{cases}$ kg. The grain will be stored for six months. Determine the integer temperature that minimises the total loss over the storage period and state the minimum total loss (rounded to the nearest kilogram).

A. 712

Correct B. 728

C. 801

D. 745

Correct Answer: B

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Question 24 View Details

A compound lever system is used to lift a plough weighing 1,500 N. The first lever (Class I) has an effort arm of 0.8 m and a load arm of 0.2 m. The load from this lever is attached to the effort arm of a second lever (Class II) whose effort arm is 0.5 m and load arm is 0.1 m. Determine the effort force that must be applied to the second lever to raise the plough.

A. 90

Correct B. 75

C. 60

D. 120

Correct Answer: B

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Question 25 View Details

A farmer inspects 200 plants for a particular disease. In the first random sample of 50 plants, 8 are diseased. In a second random sample of 150 plants, 27 are diseased. Using the combined data, estimate the overall disease incidence proportion and give the 95 % confidence interval using the Wilson score method (use $z=1.96$). Express the incidence as a percentage and the interval limits to one decimal place.

A. 19.8% (95% CI: 14.5% - 25.2%)

B. 15.2% (95% CI: 10.8% - 20.1%)

Correct C. 17.5% (95% CI: 12.9% - 23.4%)

D. 13.6% (95% CI: 9.2% - 18.0%)

Correct Answer: C

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