Assessment of Cu applications in two contrasting soils\u2014effects on soil microbial activity and the fungal community structure

Katharina M Keiblinger,Harald Berger,Franz Zehetner,Markus Gorfer,Melanie Paumann,Sophie Zechmeister-Boltenstern,Martin Schneider,Gerhard Soja,Lisa Jöchlinger,Evi Deltedesco,Axel Mentler

doi:10.1007/s10646-017-1888-y

Abstract

Copper (Cu)-based fungicides have been used in viticulture to prevent downy mildew since the end of the 19th century, and are still used today to reduce fungal diseases. Consequently, Cu has built up in many vineyard soils, and it is still unclear how this affects soil functioning. The present study aimed to assess the short and medium-term effects of Cu contamination on the soil fungal community. Two contrasting agricultural soils, an acidic sandy loam and an alkaline silt loam, were used for an eco-toxicological greenhouse pot experiment. The soils were spiked with a Cu-based fungicide in seven concentrations (0–5000 mg Cu kg−1 soil) and alfalfa was grown in the pots for 3 months. Sampling was conducted at the beginning and at the end of the study period to test Cu toxicity effects on total microbial biomass, basal respiration and enzyme activities. Fungal abundance was analysed by ergosterol at both samplings, and for the second sampling, fungal community structure was evaluated via ITS amplicon sequences. Soil microbial biomass C as well as microbial respiration rate decreased with increasing Cu concentrations, with EC50 ranging from 76 to 187 mg EDTA-extractable Cu kg−1 soil. Oxidative enzymes showed a trend of increasing activity at the first sampling, but a decline in peroxidase activity was observed for the second sampling. We found remarkable Cu-induced changes in fungal community abundance (EC50 ranging from 9.2 to 94 mg EDTA-extractable Cu kg−1 soil) and composition, but not in diversity. A large number of diverse fungi were able to thrive under elevated Cu concentrations, though within the order of Hypocreales several species declined. A remarkable Cu-induced change in the community composition was found, which depended on the soil properties and, hence, on Cu availability.

Highlights

Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Martin Schneider and Markus Gorfer contributed to this work.Institute of Soil Research, University of Natural Resources and Life Sciences, Vienna, AustriaAIT Austrian Institute of Technology, Center for Energy, Business Unit Environmental Resources & Technologies, Tulln, AustriaAIT Austrian Institute of Technology, Center for Health and Bioresources, Business Unit Bioresources, Tulln, AustriaSymbiocyte Berger, Tulln, AustriaThe infestation with foliar diseases such as downy mildew (Plasmopara viticola) and anthracnose (Elisinoe ampelina) can cause severe losses in grapevine (Vitis vinifera L.) production (Merrington et al 2002)
Six different concentrations (0, 50, 100, 200, 500, 1500, 5000 mg Cu kg−1) of a commercially available fungicide based on Cu(OH)2 (53.7% according to the product label; with a set of formulation agents that are not aimed to target activity and microbial community according to the manufacturer’s information) were applied as a suspension in water to both soils in five replicate pots each
Soil microbial biomass carbon (SMBC) was sensitive to increasing Cu concentrations at both sampling times and for both soils

Summary

Introduction

AIT Austrian Institute of Technology, Center for Energy, Business Unit Environmental Resources & Technologies, Tulln, Austria. AIT Austrian Institute of Technology, Center for Health and Bioresources, Business Unit Bioresources, Tulln, Austria. Copper (Cu)-based fungicides such as the Bordeaux mixture have been used to control these plant diseases since the end of the 19th century, and Cu compounds including Cu-oxychloride and Cuhydroxide are still applied today in both, conventional and organic viticulture as well as in horticulture (Brun et al 1998). As a consequence of the regular and frequent longterm foliar application of Cu-based fungicides, Cu has accumulated in many agricultural and viticultural soils. In surface horizons through direct application, drift, or dripping of excess sprays from leaf surfaces (Chaignon et al 2003) and because of its limited mobility, which is related to soil clay content and organic matter (Kabala and Singh 2001). In typical Austrian viticultural regions, highest Cu concentrations have been reported for the Weinviertel and Wagram, with up to 831 mg Cu kg−1 and 888 mg Cu kg−1, respectively (Berger et al 2012)

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Conclusion