Soils, climate and vine management: their influence on Marlborough Sauvignon blanc wine style

Sauvignon blanc was first planted in Marlborough, New Zealand in the mid-1970s. Since that time, Marlborough has gained an international reputation by producing the definitive wine style of that grape variety. However, within the relatively small geographic region of Marlborough, distinctive sub-regional differences in flavour and aroma profiles are now being defined. For example, wines made from fruit grown in the lower Awatere Valley (30 km south of Blenheim) typically have higher herbaceous characters, associated with higher concentrations of iso-butyl methoxypyrazine (IBMP) when compared to wines made from fruit harvested at the same soluble solids in the Wairau Valley.
Experiments conducted over the past five years have investigated the extent to which these differences in flavour and aroma profiles are a reflection of soil, climate or management (in particular grape yield and harvest date). Fruit has been harvested at a soluble solids of 21.5 to 22.5 ^o Brix on each of five vineyard sites (four in the main Wairau Valley and one in the cooler Awatere Valley), and covering a range of soil types. Vines were either trained using a 2-cane or 4-cane vertical shoot positioning system at each site, to investigate the possible effect of vine yield. The higher yields resulted in a later harvest date (the date on which 21.5 ^o Brix was reached) at each site. In general this also resulted in lower IBMP concentrations in the wines.
The results from these experiments provide winemakers with an understanding of the effect of the interaction of site, grapevine yield and harvest date on Sauvignon blanc wine aroma and flavour profile, allowing them to express the sub-regional Marlborough “Terroir” of this wine.