What a poet originally wrote is interesting, but if a song gets into the way of being transmitted orally, that's what really matters. I very much doubt if most people who sing Ragan Road learnt it from print, and that's a mark of what a great song it is.

For a song to reach the level of being passed on orally, so that everyone knows it but they don't know where they learnt it, I think that's the crown of respect for any songmaker.

But it would be interesting to know what the man wrote.

The fact that "pledge" rhymes with "ledge" doesn't in any way settle it. Rhymes aren't compulsory, and he might easily have decided to dispense with the obvious rhyme, and make it "passion play", and rhyme it in the process with the next two lines instead. My feeling is that "play" works better, but maybe that's because it's how I've always heard it sung, I think. There's supposed to be a tape in the Radio Eireann archives somewhere of Patrick Kavanagh singing it - maybe that'd settle the argument.

The other related thing here is whether to have it as "ledge", which probably is what he wrote, or "edge", which very often gets sung, and which I'm not sure isn't better.