What is the best way for irrigation potatoe plant?

Question:

Answers:
Presumably you've earthed up or ridged your plants(?)

The water needs to get to the roots - where the tubers will form - the potato is a tuber - so don't water onto the leaves. Water in between the rows and make sure you water enough to get the water down below the top crust of the soil. When the potato plant starts to flower it will need more water - that's the time to make sure that you irrigate well as the tubers will begin to develop under the soil then.