A comparison of nonchemical weed management practices on vine growth, productivity, undervine vegetation and microbial ecosystems

Abstract

Herbicides are commonly applied under vines to minimize the competition by weeds. As concerns about using fewer chemical inputs have developed, alternative methods to herbicides for undervine weed control are increasingly being adopted. These trials were carried out in New Zealand on Sauvignon blanc, Pinot noir, and Merlot from 2012/13-2015/16. Three experimental treatments were evaluated: continued herbicide, undervine mowing and undervine cultivation. Vine vegetative growth in the mowing and cultivation treatments was reduced compared with herbicide treatments, shown by larger percent canopy gaps. Berries from the herbicide treatment were larger than those of mowing and cultivation treatments in all varieties. At harvest, there were few significant differences in Brix, pH, TA, organic acids, skin anthocyanins, tannins or total phenolics. Rot incidence and severity were higher in the herbicide treatment in Pinot noir. In all varieties, undervine mowing led to reduced yields compared with herbicide. In Merlot and Pinot noir, the cultivation treatment also had significantly lower yield than herbicide. Continual treatment for four years led to a shift in the numbers and species of plants under the vines. The mowing treatment had almost 100% cover, primarily grasses and clover, under the vines. The cultivation treatment had the greatest number of undervine plant species. The herbicide treatment had the greatest proportion of bare area. The differences found in microbial communities were small, and more a factor of the variety/location than of undervine vegetation management treatments.