Under-Vine Management To Modulate Wine Chemical Profile

Conventional viticulture relies on herbicides to prevent the growth of competing vegetation under the vines. There is a drive within the industry, particularly in New Zealand, to increase sustainability, and therefore nonchemical options to deal with under-vine vegetation would be of great benefit. A very limited number of studies have considered the impact of under-vine management practices on the aroma profiles of wine. The effects of three different under-vine management approaches (mowing, cultivation and herbicide) on vine performance, soil properties and aromas of Sauvignon blanc and Pinot noir grapes and wines were considered in a commercial vineyard in Blenheim, and Merlot and Syrah in the Hawke's Bay, New Zealand. A full factorial randomised block design was developed. Vine performance (i.e.: trunk circumference, leaf area, point quadrat analysis (PQA), midday stem water potential, petiole analysis, and leaf gas-exchange), basic fruit compositional parameters (pH, TSS, TA and berry weights) and wine aroma profile were compared in the 3 treatments. There were few differences in vine physiological parameters and canopy measurements. Yield and fruit composition was not significantly affected by the treatments, indicating that ripening was not impaired by the nonchemical options. Wines made from mowed treatments showed lower pyrazine concentrations and lower 3MH and 3MHA concentrations in the Sauvignon blanc wines. These data show that nonchemical methods to control under-vine vegetation are a viable option, as they do not negatively affect the vines and are able to affect the flavor and aroma of the resulting wines.