Irrigation - Choosing the Right Pop-up Sprinkler

Do I understand correctly that if the pump curve shows that the pump delivers 1.6 m³/h of water at 4.4 bar and I run only one zone where all the sprinklers together consume exactly 1.6 m³/h, the pump will automatically adjust to 4.4 bar?

No, unfortunately not. The diagram shows a characteristic curve under standard conditions.
The number of sprinklers, their flow rate/pressure regulation, the pipe length, the pipe diameter, the elevation profile of the pipe – all of these influence the actual water volume delivered.

Use pressure regulators and you won’t have to calculate much. You can make a rough estimate and then practically adjust at the sprinkler using the pressure regulator.
You select a realistic operating range from the pump curve that provides a "buffer for practical implementation." For an operating point of 1.6 m³/h, for example, I would assume 20 l/min = 1.2 m³/h. You divide the number of sprinklers by the flow at the target pressure. This calculates the number of sprinklers that can sensibly run simultaneously – you can set the target pressure yourself.
From the sprinkler diagram, you get the throw distance. Now you can shift a few parameters back and forth to find the correct positions. Thanks to the buffer and the pressure regulator, you can compensate for small calculation errors in practice. A rough estimate is sufficient.

If you don’t want pressure regulation because it costs 300€ extra, you have to accept inconsistent pressure. Here are a few incomplete parameters to discourage you:
1. Length, pipe diameter, and material count: The pressure loss relative to the pipe cross-section is clear: With a 1/2" PE pipe, you lose about 0.35 bar over 10 m at 1.2 m³/h; with a 1" pipe, only about a tenth of that.
2. Elevation differences count. 1 m corresponds to 0.1 bar pressure (pressure gain downhill, loss uphill).
3. Simple sprinkler formula (good approximation): water volume delivered = sprinkler constant multiplied by the square root of the nozzle pressure, which corresponds to the line pressure.
Each nozzle will have a different throw distance. Happy planning!

Thank you for the detailed explanation. Could I also use just a pressure reducer directly on the valve of the respective circuit instead of the pressure-regulated housings? That would feel more flexible to me. So I would then set the pressure reducer to 3.2 bar on the valve and lay everything behind it with a 32 mm pipe. Then I would have just as good a result as with the pressure-regulated housings, right?

Could I use just a pressure reducer directly at the valve of each circuit instead of the pressure-regulated housings? That way I would feel more flexible.

Of course you can do that. However, I do not see the advantage of flexibility compared to an adjustable sprinkler – rather the opposite. I would install a premium system exactly as it is intended. Often there are a few years of experience and details behind the considerations that only become apparent when you take a detour.

The sprinkler is not adjustable. The pressure-regulated housings are all preset to a specific pressure - 2.1 bar, 3.1 bar, or 2.8 bar with Hunter. Unfortunately, this preset cannot be changed. The MP rotators operate optimally at a pressure of 2.8 bar. The R-VAN from Rainbird, on the other hand, at 3.1 bar. With a pressure reducer at the beginning, I would have the flexibility to adjust the pressure. That is what I meant by more flexibility.

I did not express myself well, or rather, incorrectly. On the Regner, you adjust the throwing distance with a little screw, not the pressure. So everything is fine with the constant pressure.

The MP rotators operate optimally at a pressure of 2.8 bar.

Yes, but only for one season. I distributed about 40 of them. After each winter, 20-40% of the nozzles had to be replaced because they no longer rotated (not even after cleaning and ultrasonic bath). The internal mechanism is very fine and therefore sensitive to any kind of dirt or lime deposits over the winter. I have now replaced almost all of them with JPG and I20 gear-driven rotors and have been doing very well with them. Only with very short throw distances or replacement of strip nozzles is this harder to implement.