I heard this story form my mother and it is as follows;
Long ago old people used to hear music and see lights in an old fort in my own townland. There was a man ploughing in the same field where the fort was. On this day the man was ploughing and a fairy came up to him and asked him what he was going to put in the field, and the man replied that he was going to set potatoes in it. Then the fairy said that if he set potatoes in it he would not be alive to dig them. The man, however, set the potatoes.
Before the time came to dig the potatoes the man died and the potatoes were left undug. So no one has ever interfered with that field since.