Question

a method of irrigation

Answer 1

There are two types of irrigation :-
1)Modern Irritation
2)Traditional Irrigation
You want only one method ,So i will give you about drip irrigation
It is a method of irrigation in which plants or crops get water drop by drop . The water is delivered at its root . This method uses small amount of water . This method saves both water and time . Mostly seen in water scarce areas. There are many more methods like pulley system, Dhekli etc.
Hope you like the answer.
THANK YOU

Answer 2

there are lot's of method for irrigation like
drip system- in this system water goes to the plant drop by drop 
there are lot more but u asked only for 1 method