I suggest that you keep the ground damp while they get established. Especially if it is hot where you are located.

They don't like to be soaked all the time, but until they get some roots grown and down into the earth, they will need to be watered more frequently.

My established irises seem to be perfectly happy when I am a bit stingy with the water.

Most people suggest watering once, then letting the ground completely dry out. Do not keep them moist if it is hot and humid out or they will rot. I live in Southern California, and I only water my new irises once a week, if that, and less in truly hot, humid weather. The rot problem is why so many irisarians suggest potting new irises up and growing them in partial shade for the first two months until fall weather comes. I'm too lazy to do that, but I did save a rhizome that had begun to rot once by cleaning it up and following that advice, and it grew much better than my other new irises.
Renee