Correction to my post- rigid side is not steel pipe; its Sch 80 PVC.

The black pipe is almost certainly polyethylene-- an excellent choice for that purpose, in my opinion.
An adapter of the style below is best. I suggest avoiding galvanized steel adapters as they will rust and will be consumed by electrolysis if directly connected to copper or brass-- but they are stronger than any non-metallic adapters.
I use two clamps at each adapter. Be sure you have the correct style and size for your pipe. The adapter should be difficult to insert and to remove-- tight fit. If not, it is the wrong one. Do not select from the irrigation fittings bin unless there is no other choice.

Here is a link that might be useful: Male barb adapter