Underpinning terroir with data: on what grounds might subregionalisation of the Barossa Zone geographical indication be justified?

Abstract

Background and Aims: Winegrowers in the Barossa Zone geographical indication of South Australia are interested in understanding subregional terroir. A previous analysis of biophysical variation over the entire Barossa Zone was not strongly supportive of the subregionalisation favoured by local winegrowers. Here, we use an updated, contemporary climate data set and focus just on land under vineyard as a platform for better understanding the biophysical component of the Barossa terroir. Methods and Results: Clustering (k-means) of digital map layers describing a range of climatic and topographic indices along with soil properties of viticultural importance was used to explore regional-scale patterns of spatial variation. Marked soil, topographic and climatic variation was noted within the Barossa Zone, and the clustering suggested a useful biophysical basis for exploring the merits of dividing the geographical indication more finely than the existing Barossa and Eden Valley regions. Conclusions: Whilst there are clear differences between the Barossa and Eden Valleys in terms of temperature, rainfall, soil fertility and the plant available water capacity of soil, the clusters identified suggest that a re-evaluation of the presently proposed subdivision of the Barossa Valley region may be warranted. Wine chemical and sensory data would need to be integrated with the biophysical data to confirm the expression of subregional terroir effects within the Barossa Valley. Significance of the Study: This data-driven analysis provides further evidence of the desirability of terroir analysis being free of the bias that is introduced by heuristics, or by examination of historically delineated terroirs, and of focussing solely on the land which is under vine in evaluating terroir.