The impact of differences in soil texture within a vineyard on vine development and wine quality

Marlborough Sauvignon Blanc has rapidly gained an international reputation for style and quality. The extent to which this can be attributed to the climate, soils or vineyard management is at present unclear. However, the young alluvial soils of the Wairau Plains are considered to play an important role in determining this unique wine style. Marked changes in soil texture occur on the Wairau Plains over short distances. These changes reflect the historical braided nature of the Wairau River, and often run at right angles (east-west) to the north-south orientation of vineyard rows. Trunk circumferences were measured on whole rows of vines in a vineyard on the Wairau Plains to identify vines exhibiting different vigour levels. Vine vigour as reflected by trunk circumference and pruning weight was increased with the depth to gravel, while fine root density was greater in the gravelly phases of the soil profile. Vine phenology was more advanced where vines were growing on gravelly soils, in particular time of flowering (by 3 days), veraison (by 7 days), soluble sugars at harvest (by 11 days) and the onset of leaf senescence (by 60 days). We conclude that within a vineyard, the higher the proportion of gravelly soils, the more advanced the vine phenology and the riper the fruit and ultimately wine style will be on a particular date.