How to choose suitable pump for irrigation?

When you buy a pump, you will try to find a pump that has the total head you require at the flow you require.
That means you first have to know what total head you need and at what flow rate.

Specification pump is the last step In the design of irrigation systems.
Must initially determine the irrigation method, and then make sure to deliver the required quantities for each plant and then calculate the aggregate disposition per valve and then selecting diameter outlet and then selecting irrigation pump, depending on the specifications companies producing publications Pumps

you have to determind the pump first and take in your consider the economy side for saving power  which mean save money so your design efficiency and hydraulic calculation about the head losses and amount of flow required for the system also  the  time for operation

you can study the efficiancy curve of the pump and then you will be able to choose the right one which Complies with your requirements