Child was extrememly sarcastic of most of Peter Buchan's contributions.
Buchan was criticised heavily at the time over his 'eking out' of his versions, and excused himself from any corruption by blaming a blind itinerant, Jamie Rankin' (who he'd only known for a few years) who he claimed had collected most of the ballads for him. The term 'fall guy' comes to mind.
Towards the end of Child's collection you will find at least a dozen ballads that occur only in the published collection of Peter Buchan. It is worth reading Child's summary of what he thought of these later contributions on p182 of volume 5 in the introduction to another of Peter Buchan's sole concoctions.
Abby's comment on the 18th March 01 is quite pertinent.
Buchan was well read and took his themes for his ballads from a variety of sources, some classical, some from Scandinavian ballads, some from English broadsides.
He left no field notes of any description. The 3 existing manuscripts are actually proofs for the publications he produced.