Sam Henry ,who published the song in 1926, states that Bawn or Bawnboy is in Co.Cavan.   
He gives the last verse as :

I wish the queen of England had sent for me in time,
And placed me in some regiment all in my youthful prime .
I'd fight for England's glory from clear day light of dawn
And I never would return again to plough the Rocks of Bawn.

"Bawnboy (Irish: an Bádhún Buí, meaning "the yellow bawn") is a small village in a valley at the foot of Slieve Rushen, between Ballyconnell and Swanlinbar, in County Cavan, Ireland. The current population is about 250. A bawn is the defensive wall surrounding an Irish tower house. It is the anglicised version of the Irish word badhún meaning "cattle-stronghold" or "cattle-enclosure" – its original purpose was to protect cattle during an attack. The remains of a late medieval bawn is to be seen at Bawnboy House, which is the origin of the village name."........ wiki

this is from Sir Charles Coote in his 'Statistical Survey of County Cavan' quoted in the wiki entry on Bawnboy : "No part of Cavan is less engaged in manufacture........ nor are there any lands so favourably disposed for improvement, if we consider the small rents,and the valuable change, which is wrought on the soil of this hilly region by a small applicationof lime, and a little persevering industry."