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

The design principles incorporated into the sprayers of a centre-pivot system to ensure equal water distribution include:

1. Size of Sprayer Nozzles: Smaller nozzles are used at the center and gradually increase in size toward the outer edge to account for varying pressure.

2. Pressure Regulation: A pressure regulator is applied to ensure uniform water delivery across different sections of the pivot.

3. Wheel Speed Adjustments: Wheels move at different speeds depending on their position in the pivot to maintain even distribution despite differences in travel distance.

4. Field Layout Considerations: The system is designed considering topography, soil types, and kinds of crops to optimize water application.

Calibration of the water distribution system on a centre pivot is essential for several reasons:

1. Movement Dynamics: Since the centre pivot moves in a circular pattern, the outer circles cover a larger area and thus require more water. Calibration ensures that water is distributed proportionally based on the distance travelled by each section.

2. Soil and Crop Variability: Different areas may have varying soil types and crop needs; calibration helps adjust water volume accordingly, optimizing plant growth and preventing over-irrigation.

3. Pressure Adjustments: It is necessary to adjust the distribution based on land gradient and pivot speed to maintain the required pressure across all nozzles.

Two common soil problems due to incorrect calibration of water distribution are:

1. Soil Erosion: Inconsistent water application can lead to soil being washed away, especially in areas that receive excess water.

2. Nutrient Leaching: Over-irrigation can cause nutrients to leach from the soil, resulting in salinity issues or reduced fertility, negatively affecting crop yields.

A commonly used device to determine soil water content is the Neutron Probe. It is essential in irrigation management because:

• It provides accurate measurements of soil moisture, which helps in scheduling irrigation effectively.
• It aids in ensuring that plants receive the optimal water supply, preventing both over-watering and under-watering.

Evapotranspiration in maize crops is measured because it is crucial for:

• Water Management: Understanding evapotranspiration helps manage water use efficiently, aligning irrigation schedules with crop requirements.
• Crop Health Monitoring: It serves as an indicator of crop health, revealing whether crops are under stress due to low water availability.

To calculate flow rate, we use the formula:

ext{Flow Rate} = rac{ ext{Total Volume}}{ ext{Time}}

1. Convert time to seconds: 5 minutes = 300 seconds.
2. Total Volume = 15,000 litres.
3. Now apply the values:

ext{Flow Rate} = rac{15,000 ext{ litres}}{300 ext{ seconds}} = 50 ext{ litres/second}

Thus, the flow rate is 50 litres/second.

The type of water purification system is a counter current purification system or faucet purification system.

The water purification system operates through the following steps:

1. Pre-filtration: Water first passes through three distinct membrane filters.
2. Filtering Process: The first membrane removes larger particles, while the second captures smaller particles.
3. Final Treatment: The last cartridge often includes a water softener that ensures any remaining impurities are filtered out, leaving purified water ready for use.

The process is known as Reverse Osmosis.

The breakdown of household sewage in a septic tank involves several stages:

1. Anaerobic Digestion: Bacteria break down organic matter in an oxygen-free environment, reducing the volume of waste.
2. Solids Settlement: Solid waste settles to the bottom, forming sludge while lighter materials float as scum.
3. Effluent Filtration: The remaining liquid (effluent) exits the tank through a drain field where it is further filtered by soil, removing harmful contaminants.