I keep having the same sort of argument with different people about terroir and whisky, most recently with @maltreview and @WhiskyPilgrim. Since Twitter doesn't lend itself well to lengthy exposition, here's a blog post instead.
The notion of terroir is deeply bound up with wine, and with France. The word itself is French, although my copy of Hachette unhelpfully translates it as "land". The Oxford Companion to Wine offers the slightly more useful "total natural environment of any viticultural site". The Companion then goes on for some two or three thousand closely spaced words which—and I hope my twitter antagonists can agree—don't really serve to settle the matter definitively.
But I think all sides can agree that a terroir wine has flavours unique to the place where its grapes were grown and where it was made.
How, then, does this idea transpose into Scotch whisky? I would argue that it doesn't.
We can straight away disregard the hundred plus distilleries who buy their malt from Crisps or Bairds or whatever, since that barley is sourced from all over the UK and beyond. For them, there can not be the total natural environment of the triticultural site. Their barley is not site specific.
But even when we look at Springbank or Bruichladdich or Ballindalloch, the idea of a flavour unique to the place where the barley is grown does not stand up to any sort of scrutiny.
That's because the analogy with winemaking is just that, an analogy - and a poor one at that. Wine is the all but inevitable consequence of not drinking the grape juice, of leaving the juice to rot. Humans need do little more than pick and press the grapes and something wonderful (or at least drinkable) will result. Whereas whisky is the end result of a multi stage process, with each stage contributing flavours. The human element is far more important than in wine making.
From the peating level of the malt to the length of fermentation to the shape of the stills to how the stills are run to the choice of casks, all these human choices contribute much more than the place where the barley is grown.
We see this in the resulting product. Yes, Bruichladdich's Islay barley bottlings are slightly different from their Scottish barley expressions - but they are unmistakeably, first and foremost, Laddies. And Springbank's Local Barley bottlings differ from other Springers of similar age and cask type, but they are most definitely Springbank.
By contrast, were Laphroaig to take barley from Rockside farm and turn it into whisky according to the Laphroaig method and procedure, which would it more resemble, Laphroaig 10 or Bruichladdich Islay Barley?
The unvoiced answer to this rhetorical question is why we talk about distillery character and not barley field character. Whisky terroir does not exist.