There are some other references, none early though.

Just The Way It Was: Tommy Dan Tims Derrinageer, Ballinaglera A true story of a traditional farm life in County Leitrim, Ireland - 2007 (according to amazon): The corn meal was called Indian buck. It was good for the chickens and we could also make porridge from it

A bit earlier is this 1940s publication quoting The Cornell Countryman of 1922 Corn in the development of the civilization of the Americas : a selected and annotated bibliography (p6)! The Indian 'Buck' corn was planted by the pioneer whites and became our 'York State Flint,' and it was the sight of this corn growing six feet high on the banks of the Susquehanna that induced the members of the Sullivan expedition to sell their military grants to enter what is now Tioga, Chemung, Broome, and Tompkins
Counties.

There's also a reference in the Ballad Index to an alternative title for Bad Luck Attend the Old Farmer, but again no idea how old the reference is. It was collected in 1980 in Fermanagh, Northern Ireland.

Nothing definite before the song era as you say.

Mick