neco 2021 agricultural_science | Practical

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Question 1 View Details
A farmer wishes to evaluate the effect of intercropping maize with cowpea on insect biodiversity in a 0.5 ha field. He uses a sweep net to sample insects from five randomly selected 10 m × 10 m quadrats in the maize‑only section and five quadrats in the intercropped section. The total numbers of individuals of each insect species recorded from the ten quadrats are shown in the table below. | Species | Maize‑only (total individuals) | Intercropped (total individuals) | |---------|------------------------------|----------------------------------| | A | 30 | 20 | | B | 20 | 25 | | C | 15 | 20 | | D | 10 | 15 | | E | 5 | 10 | Using this data, answer the following:
Question Parts
(a)
Calculate the average species richness (average number of different species) per quadrat for the maize‑only section and for the intercropped section.
(b)
Using the pooled data for each section, compute the Shannon‑Wiener diversity index (H') for the maize‑only section and for the intercropped section. Use natural logarithms and give H' to two decimal places.
(c)
Based on the results obtained in (a) and (b), advise the farmer whether intercropping has increased insect biodiversity and give one practical recommendation to enhance the benefit.
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Question 2 View Details
A soil sample taken from a cultivated field is analysed for particle‑size distribution using the hydrometer method. The following data were recorded after temperature correction and dispersing‑agent adjustment: - Oven‑dry soil mass weighed: 50.0 g - Hydrometer reading at 40 s (sand fraction): 30.0 g L⁻¹ - Hydrometer reading at 2 min (sand + silt fraction): 20.0 g L⁻¹ - Hydrometer reading at 5 min (sand + silt + clay fraction): 8.0 g L⁻¹ - Specific gravity of soil particles: 2.65 - Density of water at 20 °C: 1.00 g cm⁻³ - Hydrometer calibration factor: 1.0 (no correction needed) Assume the hydrometer cylinder volume is exactly 1 L and that the dispersing agent adds negligible mass. Answer the following:
Question Parts
(a)
Calculate the percentage of sand, silt and clay in the sample.
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Question 3 View Details
A farmer wants to compare the effectiveness of three hand tools – hand hoe, garden fork and spade – for breaking a compacted soil layer of 15 cm depth over a rectangular plot measuring 2 m by 3 m. The farmer records the time taken to loosen the soil completely with each tool as follows: hand hoe 12 minutes, garden fork 9 minutes, spade 7 minutes. The masses of the tools are: hand hoe 2.5 kg, garden fork 3.0 kg, spade 2.0 kg. The farmer applies a constant average force equal to twice the weight of the tool during each stroke, and each forward stroke covers a linear distance of 0.5 m across the full 2‑m width of the plot. Using these data, answer the questions that follow.
Question Parts
(a)
Calculate the average power output (in watts) of each tool during the operation.
(b)
Based on the calculated powers, recommend the most efficient tool and give a brief justification.
(c)
Mention two possible sources of error that could affect the recorded times.
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Question 4 View Details
A 45 kW tractor operating at 2000 rpm is used to pull a moldboard plough across a field of 5 hectares. The draft force required by the plough depends on soil moisture content as follows:\n- 10% moisture: 2500 N\n- 15% moisture: 2000 N\n- 20% moisture: 1500 N\nThe field has an average moisture content of 12%. The tractor moves at a constant speed of 5 km/h and the plough width is 2 m. The tractor’s specific fuel consumption is 0.25 L per kWh of engine output. Using this information, answer the questions below.
Question Parts
(a)
Determine the average draft force required for the 12% moisture condition by linear interpolation.
(b)
Calculate the power required to pull the plough at the given speed.
(c)
Estimate the total fuel consumed to cultivate the whole 5‑ha field.
(d)
List three possible sources of error when measuring the draft force in the field.
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