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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
- Estimate Flow and Pressure Requirements: The farmer must start by estimating the necessary flow rate (litres per minute) and pressure (bar) required for the irrigation system based on the area and type of crops being irrigated.
- Select Pump Type: Decide on the type of pump that best suits the irrigation needs, whether it's a centrifugal pump, submersible pump, or jet pump.
- Research Pump Models: Investigate different pump models available in the market that fit the chosen type. Consider reliability, brand reputation, and operational efficiency.
- Design a Draft Irrigation System: Create an initial draft irrigation design to understand how the pump will fit into the overall irrigation scheme. This helps in determining the pressure and volume needs.
- Cost Evaluation: Finally, return to compare the shortlisted pump models based on the budget and long-term operational costs to select the most cost-effective option.
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 of a centre-pivot system ensure efficient water distribution. These include:
- Sprayer Size Variation: The sprayer nozzles are designed to vary in size, being smaller at the center and larger towards the end of the pivot, ensuring that water covers a larger area as distance increases.
- Pressure Regulators: Incorporating pressure regulators ensures equal water pressure at all points, leading to uniform distribution.
- Wheel Speed Adjustment: The wheels on the outer pivot move faster than inner wheels; hence, the system accounts for the difference in speed by adjusting the water distribution accordingly.
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 of a centre pivot's water distribution system is crucial for several reasons:
- Movement Dynamics: The centre pivot rotates, and the outer wheels cover a larger circle. Calibration ensures that the volume of water is consistent across varying distances.
- Impact of Land Layout: Variations in slope and soil type affect water absorption; thus, calibration is necessary to adjust for these factors.
- Optimal Crop Growth: Proper calibration leads to efficient irrigation, minimizing overwatering or underwatering, which can stress crops.
Step 4
State TWO common soil problems when water distribution is not correctly calibrated in an irrigation system.
Answer
- Soil Erosion: Improper distribution may lead to runoff, washing away the topsoil.
- Under or Over Irrigation: Inconsistent water application can lead to dry patches or waterlogged areas, both detrimental to 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
- Device Name: Neutron Probe.
- Necessity: This device measures soil water content accurately, helping farmers schedule irrigation effectively to promote optimal plant growth and prevent under or over-irrigation.
Step 6
Explain why evapotranspiration is measured in a maize crop.
Answer
Evapotranspiration is a critical measurement in maize cultivation because:
- Water Management: It helps in determining the amount of water the crop requires.
- Scheduling Irrigation: Understanding evaporation rates allows farmers to schedule irrigation more effectively, maximizing crop yield.
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:
- Volume of Water: 15,000 litres.
- Time Taken: 5 minutes = 300 seconds.
- Flow Rate Calculation: Flow Rate = Volume / Time = 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 as follows:
- Filtration Process: Water undergoes filtration through three different membrane filters, each designed to trap and remove particulates of varying sizes.
- Multiple Membranes: The first membrane captures larger particles, with subsequent membranes filtering out smaller contaminants.
Step 10
Step 11
Describe the process of breaking down household sewage in a septic tank.
Answer
The process involves:
- Bacterial Breakdown: Sewage is anaerobically broken down by bacteria present in the septic tank.
- Slow Decomposition: Only a small portion remains in the tank while most of it is transformed into simpler substances, which allows for cleaner effluent to be released into the drain field.