Optimising Resources for Farm Sustainability

Maintenance and Water Distribution Uniformity in Pivot and Linear Irrigation Systems

Farm sustainability greatly relies on the efficient use of resources, particularly water. Centre pivot and Linear irrigation are known for its high-water efficiency. It delivers water directly to the crops with minimal wastage. By using pressure regulated nozzles this ensures that a higher percentage of water reaches the plant's root zone.

This article discusses the importance of water application uniformity in pivot and linear irrigation systems and with tips on how to maximise uniformity through regular maintenance and assessments.

The Importance of Water Distribution Uniformity

Water distribution uniformity is crucial for irrigation system performance because it ensures that every part of the crop receives the right amount of water. A well-designed irrigation system will typically achieve a distribution uniformity greater than 0.8 in ideal conditions. However, reduced uniformity can lead to dry patches or overwatering, both of which can have negative environmental and economic impacts.

Common Causes of Poor Uniformity

Poor uniformity in water application in irrigation systems can result from several factors, including:

·???????Inadequate pump operating pressure or flow rate

·???????Incorrect nozzle size and placement

·???????Worn or clogged nozzles

·???????Missing sprinkler head

·???????Leaking boots

·???????Incorrect control panel settings

Addressing these issues is essential for preventing yield losses, reducing pumping time, and decreasing energy use, ultimately lowering irrigation costs.

We will explore common problems that can be identified during bucket testing that affect the uniformity and provide solutions to improve it.

Blocked Nozzles

Blocked nozzles are a frequent issue in pivot and linear irrigation systems and can result in irregular spray patterns and inconsistent uniformity. Sediments, spiderwebs, and other particulate matter, including effluent, can obstruct the nozzles. It is recommended to visually inspect the blocked nozzles by removing one from the sprinkler body and checking for any particulates.

Worn Nozzles

Over time, sprinkler nozzles can wear out, leading to changes in the diameter of the nozzle hole. This alteration affects the application depths and overall uniformity. The material composition of nozzles can influence their wear rates, with thermal plastic nozzles having an effective operating life of around 8-10 years. Regularly inspect the nozzles and replace them if necessary to maintain uniformity.

Worn Regulators

Pressure regulators are responsible for maintaining uniform pressure and flow across the irrigator. Over time, these regulators can wear out, causing an increase in flow through affected regulators and resulting in uneven application depths and reduced uniformity. To test the functionality of a regulator, attach a pressure gauge below it. If the pressure reading is within 10 percent of the regulator's specified pressure, it is functioning correctly. Look for jagged patterns on the pressure graph, which may indicate worn regulators.

Low Pressure

Insufficient pressure can cause irrigation systems to underperform, affecting both distribution uniformity and application rates. If the application rate decreases as you approach the end gun, it is likely due to a pressure issue. Check the inlet pressure at the irrigator centre to ensure it meets the required sprinkler pressure. Additionally, screw a pressure gauge above the regulator at the far end of the irrigator to verify that the pressure is at least 5 psi higher than the pressure regulator. Insufficient pressure at the far end indicates an inefficient system.

Solenoids

Corner arm solenoids control the opening and closing of the corner arms in pivot systems. These solenoids can wear out over time, potentially leading to them remaining open and causing disruptions in distribution uniformity and application rates. Look for visible signs of water spraying out, as this indicates solenoid wear and malfunction.

Corroded Pipework

Water hardness can affect the pipe's inner surface, leading to corrosion and reduced pressure and flow. Hard water contains dissolved minerals such as calcium and magnesium, which can precipitate and form an inner layer in the pipe. This deposition reduces the inner surface area, negatively impacting application rates. Regularly check for signs of corrosion and address any issues promptly to maintain efficient water flow.

Leaking Pipework and Boots

Leaking pipework, boots, and hoses can result in excess water application, leading to disruptions in distribution uniformity and application rates. During bucket testing, observe the irrigator while it is running and note any excess water and its location along the irrigator. Repair any leaks to prevent water wastage and maintain uniformity.

Incorrect Settings

The irrigator relies on programmed panel constants for its travel speed and therefore its applied depth. Check that the latest up-to-date sprinkler chart constants are calibrated and lined up with the irrigator panel.?

Conclusion

Irrigation system performance relies on the efficient use of resources, and optimising spray irrigation systems is crucial for achieving this goal. In addition, regular maintenance and assessments can help ensure water distribution uniformity and reduce the negative impacts of poor water management. By checking these points, growers can achieve better water management.

Written by

Ignacio Esnaola

Performance Assessment Specialist

p 027 444 5137

e [email protected]

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Contact WaterForce for more information

p 0800 436 723

e [email protected]

w waterforce.co.nz