Understanding Drip Irrigation
Systems and what are PC or NonPC Drippers?
Within Drip Irrigation Systems, from a technical and hydraulic point of view, irrigation drippers are divided into two categories:
- Non-PC Drippers: equipped with a labyrinth that control output by forcing a turbulent flow.
- PC Drippers (flow regulated): equipped with a labyrinth and diaphragm that maintain a constant flow rate even when pressure in the pipe fluctuates.
With all driplines, when laid out on a flat terrain, the water pressure in the beginning of the lateral is highest, while gradually declining along the lateral.
The flow from non-compensated drippers is proportional to the pressure and is therefore higher at the beginning of the line compared to the flow at the end of the line.
With very long laterals, the difference can be significant.
In contrast, PC drippers emit a uniform flow from the first to the last dripper. This uniformity provides an even irrigation rate regardless of the dripper’s position along the line, which in turn allows longer stretches of driplines.
Different types of compensation mechanisms for different drip irrigation systems. All types of mechanisms for drip irrigation systems have a flexible membrane, but its position is different for each mechanism type.
- Slit regulation: the simplest mechanism, without a labyrinth.
- Differential pressure: the membrane is located between two pressure zones: before and after the labyrinth. The membrane is pressed onto a small path and as pressure differential changes, the water path changes accordingly.
- Labyrinth regulation: is also a type of differential flow regulation, but in this one a large membrane is pressed directly on the labyrinth. When pressure ceases, the membrane moves away from the labyrinth allowing the dirt to flow away. This is the only dripline that has a self-cleaning mechanism which maintains the labyrinth clean as well.
You’ve already decided on drip irrigation systems, but which drippers to choose?
On a flat terrain, when the required length of laterals is within the recommended length, the non-compensated dripline is a cost-effective choice. Short rows are common in manually harvested vegetables, pulses and small orchards.
For mechanized agriculture, longer rows are common, and it is advantageous to use PC driplines.
On undulated or steep topography, non-compensated driplines will emit less water in the elevated sections and more on the lower sections, while PC drippers will maintain the same flow rate along the entire lateral and safeguard uniform growth along the row.
Understanding what advanced features innovative drip irrigation systems like Metzer can offer on selected driplines:
- Self-cleaning: With this feature, at the beginning and at the end of any irrigation cycle the regulation chamber opens wide, allowing effective flushing of dirt that has accumulated in the labyrinth. This cleaning process is important especially with poor water quality.
- Anti-Syphon: Especially designed for sub-surface irrigation, the Anti-Syphon mechanism prevents soil particles from being sucked into the drippers when irrigation is shut off.
- Non-drain system: With this feature, when the irrigation is shut off, the diaphragm moves down and blocks the water passage preventing evacuation of water from the pipes. This feature is very useful for pulse irrigation where the dripline needs to always stay full of water, allowing frequent, very short irrigation intervals, as necessary in super-intensive crop production systems. This feature shortens the response time of the pulse ensuring that application uniformity is maintained.