Effects of Glyphosate-, Glufosinate- and Flazasulfuron-Based Herbicides on Soil Microorganisms in a Vineyard

Karin Mandl,Edith Gruber,Johann G Zaller,Barbara Friedrich,Clemens Cantelmo,Florian Faber

doi:10.1007/s00128-018-2438-x

Abstract

In a vineyard we examined the effects of broad-spectrum herbicides with three different active ingredients (glyphosate, glufosinate, flazasulfuron) on soil microorganisms. Mechanical weeding served as control treatment. Treatments were applied within grapevine rows and soil samples taken from there in 10–20 cm depth 77 days after application. Fungi were analyzed using classical sequencing technology and bacteria using next-generation sequencing. The number of colony-forming units (CFU) comprising bacteria, yeasts and molds was higher under flazasulfuron compared to all other treatments which had similar CFU levels. Abundance of the fungus Mucor was higher under flazasulfuron than glufosinate and mechanical weeding; Mucor was absent under glyphosate. Several other fungi taxa were exclusively found under a specific treatment. Up to 160 different bacteria species were found – some of them for the first time in vineyard soils. Total bacterial counts under herbicides were on average 260% higher than under mechanical weeding; however due to high variability this was not statistically significant. We suggest that herbicide-induced alterations of soil microorganisms could have knock-on effects on other parts of the grapevine system.

Highlights

With an increasing intensification of viticulture, chemical weed control within and between grapevine rows is more widely used (Keller 2015)
Weeds compete with vines for water and nutrients and herbicides are used to avoid trunk damage caused by mechanical weeding machinery and to reduce working time spent in the vineyard
While effects on soil organisms of fungicides and/or insecticides have been reported from vineyards (Paoletti et al 1998), very little is known on the impacts of herbicides (Zaller et al 2018)

Summary

Introduction

With an increasing intensification of viticulture, chemical weed control within and between grapevine rows is more widely used (Keller 2015). Among the most often used herbicides in vineyards are those based on the active ingredients glyphosate, glufosinate and flazasulfuron (Bauer et al 2017). A few studies investigated soil microbial communities in vineyards (Fernández-Calviño et al 2010; Likar et al 2017; Samad et al 2017; Steenwerth et al 2008; Zaller et al 2018). A study reports significant different microbiomes between grapevines roots and rhizosphere and weeds (Samad et al 2017). The objective of the current study was to examine potential effects on soil microorganisms of three commonly used herbicides in comparison to mechanical weeding. Studies on herbicide effects on soil microbial communities can help developing more sustainable weed control measures for vineyard management

Objectives

Methods

Results