Herbicide Reduction Through Organic Undervine Treatment and Its Impact on Malbec Wine Volatile Composition
Kenneth Olejar,* M. Carmo Vasasconcelos, Petra
King, Richard Smart, Karen Ball, and Stewart Field
*Lincoln University, Department of Wine, Food and Molecular Bioscience, PO Box 85084, 7647, New Zealand (Kenneth.OlejarJr@lincoln.ac.nz)
Viticultural practices to control the undervine environment have relied on chemical herbicides. The plants they sought to control have become resistant, and many herbicides are now banned or toxic residues have been found in foodstuffs. As a result, we examined alternative methods to reduce/eliminate chemical applications to not only control undervine growth but also to ensure the resulting fruit could produce wines of equal or better quality. Three treatment groups: control (conventional practice) and black or white weedmat were assessed on mature planted Malbec vines in the Hawke’s Bay region of New Zealand. Treatments were initiated during dormancy 2015 in a randomized block design, with replicates grouped according to trunk diameter. Viticulture data was collected over the 2016 to 2018 vintages, with small-scale wines (12 kg ferments) produced in 2017 and 2018 through a standardized vinification process to simulate commercial ferments. Aromatic analysis was completed on the wines by gas chromatography-mass spectrometry to elucidate differences that may affect the quality. Additionally, high-performance liquid chromatography (HPLC) was used to quantify select phenolic compounds. There were no statistical differences in vine yield or bunch number over the three seasons. Wines demonstrated aromatic differences by analysis of variance (ANOVA) between the treatment groups and control, with the black weedmat having the greatest number of components increased in 2017. By the 2018 vintage, the aroma components were equivalent to the control. Principal component analysis of the data supports the ANOVA interpretation. Total phenolic content showed no differences; however, HPLC analysis was able to elucidate a few differences. This study demonstrates that sustainable organic methods to control the growth of undervine plants can be done effectively with the application of weedmat. It also highlights that this method of undervine treatment does not hinder yield or perceived wine quality.
Funding Support: Eastern Institute of Technology