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6.1 Explain the basic steps that a farmer should follow when selecting a pump for a specific irrigation system - NSC Agricultural Technology - Question 6 - 2017 - Paper 1
Question 6
6.1 Explain the basic steps that a farmer should follow when selecting a pump for a specific irrigation system. 6.2 Centre-pivot irrigation systems are very efficie... show full transcript
Worked Solution & Example Answer:6.1 Explain the basic steps that a farmer should follow when selecting a pump for a specific irrigation system - NSC Agricultural Technology - Question 6 - 2017 - Paper 1
Step 1
Explain the basic steps that a farmer should follow when selecting a pump for a specific irrigation system.
Answer
To select an appropriate pump for a specific irrigation system, a farmer should:
- Estimate Flow and Pressure Requirements: Determine the necessary flow rate and pressure head required for the irrigation system based on the field's water needs.
- Choose the Pump Type: Evaluate different types of pumps such as centrifugal, submersible, and jet pumps to find the most suitable model for the specific irrigation setup.
- Research Pump Models: Conduct thorough research on available pump models to assess their reliability, efficiency, and compatibility with the irrigation system.
- Draft an Initial Design: Create a draft irrigation design outlining how the pump will integrate with the system to meet water supply needs.
- Check Cost and Efficiency: Return to assess the costs. Choose a pump that not only meets the irrigation requirements but is also cost-effective.
Step 2
Discuss the design principles that are incorporated into the sprayers of the centre-pivot system to ensure the equal distribution of water from the centre of the pivot to the outer end of the pivot.
Answer
The design principles for the sprayers include:
- Sprayer Nozzle Size: Smaller nozzles at the centre and larger nozzles at the end ensure that water distribution is uniform as it travels along the pivot.
- Pressure Regulation: Pressure regulators help equalize the pressure across all nozzles, ensuring consistent flow.
- Wheel Movement: The speed of the wheels varies, requiring specific calibration to ensure water is distributed evenly despite the wheels moving at different rates.
Step 3
Explain why calibration of the water distribution system on a centre pivot is necessary. Refer to the movement of the centre pivot and the layout of the land.
Answer
Calibration is necessary because:
- Unequal Distribution: As the centre pivot moves, outer wheels cover more distance which can lead to unequal water distribution unless properly calibrated.
- Land Topography: Variation in land slope can affect how water reaches different parts of the field, requiring adjustments in the distribution system to ensure uniform coverage.
Step 4
State TWO common soil problems when water distribution is not correctly calibrated in an irrigation system.
Answer
Common soil problems include:
- Soil Erosion or Runoff: Incorrect calibration can lead to excessive water flow, causing soil erosion.
- Under/Over Irrigation: This can lead to waterlogged conditions or insufficient moisture, adversely affecting crop health.
Step 5
Name a device that can be used to determine soil water content and explain the necessity for such a device in irrigation management.
Answer
A commonly used device is the Neutron Probe. This device measures the soil moisture levels, ensuring that irrigation schedules are optimized to prevent both under-irrigation and over-irrigation, which are crucial for maintaining healthy crops.
Step 6
Explain why evapotranspiration is measured in a maize crop.
Answer
Evapotranspiration is measured to determine the crop's water needs accurately. It helps in scheduling irrigation by accounting for water loss through evaporation from the soil and transpiration from the plant. Understanding these rates ensures efficient water management, particularly during critical growth phases.
Step 7
Calculate the flow rate of water in a pipe delivery system when it takes 5 minutes to fill a 15 000 litre tank. Show ALL calculations.
Answer
To calculate the flow rate:
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Volume of Water: 15,000 litres.
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Time Taken: 5 minutes = 300 seconds.
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Flow Rate Formula:
Flow Rate = Volume / Time
Flow Rate = 15,000 litres / 300 seconds = 50 litres/second.
Step 8
Step 9
Describe the working of the water purification system in QUESTION 6.5.1.
Answer
The water purification system operates by:
- Filtration Through Membranes: Water is filtered through multiple membranes that target different particle sizes.
- Particle Separation: The system utilizes one membrane to capture larger particles, while subsequent membranes filter out smaller contaminants.
- Clean Water Collection: The final step involves collecting purified water, while remaining impurities are flushed away.
Step 10
Step 11
Describe the process of breaking down household sewage in a septic tank.
Answer
In a septic tank, sewage undergoes anaerobic decomposition, where bacteria break down organic matter.
- Sedimentation: Solids settle at the bottom forming sludge, while less dense materials float to the top forming scum.
- Bacterial Action: Anaerobic bacteria act on the solids, facilitating breakdown into simpler compounds.
- Effluent Discharge: The treated liquid effluent exits the tank to drainage fields for further treatment.