Photo AI
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 a pump for an irrigation system, a farmer should follow these steps:
-
Estimate Flow and Pressure Requirements: Determine the necessary flow rate and pressure based on the irrigation system type and the specific crop needs.
-
Choose Pump Type: Evaluate various pump types (e.g., rotary, centrifugal, submersible) to find one that suits the requirements best.
-
Research Pump Models: Investigate different pump models on the market, considering reliability, efficiency, and reviews.
-
Draft an Irrigation Design: Create an initial irrigation design that includes calculations for the pressure and volume the pump must handle.
-
Cost Analysis: Compare the initial pump choices' costs and long-term operational costs to ensure a cost-effective decision.
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 sprayers in a centre-pivot irrigation system focus on even water distribution:
- Variable Nozzle Sizes: The nozzles at the center are smaller and increase in size towards the outer end, ensuring adequate pressure and water distribution.
- Pressure Regulation: A pressure regulator is installed to equalize pressure across nozzles, preventing uneven water flow.
- Spacing of Sprayer Nozzles: Sprayers are placed further apart on the outer edges to maintain a consistent delivery rate, accommodating for the rotational speed differences of the pivot.
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 the water distribution system is crucial due to:
- Movement of the Centre Pivot: As the pivot moves, the outer wheels travel greater distances and need to move faster than those of the inner wheels to ensure even delivery of water.
- Land Layout: Factors such as topography and soil type affect drainage and water absorption, necessitating adjustments in the watering schedule 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 due to poor calibration include:
- Soil Erosion: Improper distribution can lead to excessive water flow, washing away topsoil and nutrients.
- Salinization: Inadequate watering can cause salts to accumulate, leading to brackish soil and affecting crop growth.
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 common device used to determine soil water content is the Neutron Probe. This device is essential in irrigation management to:
- Ensure Optimal Plant Growth: It provides soil moisture levels needed for crops.
- Prevent Over- or Under-Irrigation: It helps in scheduling irrigation based on current moisture levels, optimizing water use.
Step 6
Explain why evapotranspiration is measured in a maize crop.
Answer
Evapotranspiration (ET) is measured in maize crops to:
- Schedule Irrigation: ET helps to gauge how much water is lost through evaporation and plant transpiration, allowing for more accurate irrigation scheduling.
- Assess Water Needs: Understanding ET rates enables farmers to manage water use efficiently according to the growth stages of maize.
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, we use the formula:
Where:
- Content = 15,000 litres
- Time = 5 minutes = 300 seconds
Substituting the values:
Thus, the flow rate is 50 litres per second.
Step 8
Step 9
Describe the working of the water purification system in QUESTION 6.5.1.
Answer
The water purification system works as follows:
- Sequential Filtration: Water passes through multi-stage filters, with the first stage removing larger particles and the second targeting smaller particles.
- Sterilization: The final filter stage acts to eliminate any remaining contaminants, ensuring the water is suitable for consumption.
Step 10
Step 11
Describe the process of breaking down household sewage in a septic tank.
Answer
In a septic tank, sewage is anaerobically broken down by bacteria:
- Decomposition: Bacteria feed on organic matter, breaking it down into simpler substances.
- Sedimentation: Solid waste settles to the bottom, forming sludge, while lighter materials float to the top as scum.
- Effluent Treatment: The clear liquid, known as effluent, exits the tank for further treatment or absorption into the soil.