Managing copper inputs to viticultural soils for the protection of soil fertility

Copper-based fungicides have been used in vineyards throughout the world since the end of the 19th century protect against fungal diseases. However, this use results in an accumulation of copper (Cu) in surface soils which may cause negative effects to soil biota (e.g. earthworms, micro-organisms), and have implications for the long-term fertility and sustainability of these agricultural soils. Due to concerns around the environmental risks, there are societal and regulatory pressures to enforce restrictions on the use of Cu-based fungicides. Such regulatory restrictions have come into force in some jurisdictions, for instance as a requirement of re- the European Commission require member states to take steps to ensure that the rate and number of Cu-based fungicide applications are the minimum to achieve desired effects. However, assessment of the risks posed by Cu-based fungicide residues in vineyard soils has received relatively little attention in Australia. As such, scientific information is needed to characterise the risks currently posed by Cu-based fungicide residues in Australian vineyard soils and to inform decisions on the future management of Cu-based fungicides. These decisions need to consider the environmental risks of replacement chemicals as they may not necessarily pose a lower risk. Unfortunately, there is relatively little information on the environmental fate and ecotoxicological effects of alternative synthetic organic fungicide compounds. This project aimed to determine the risks that Cu-based fungicide residues currently pose to soil organisms in Australian vineyards, and how these risks vary across different viticultural regions. It also aimed to contribute towards a relative risk assessment of synthetic organic compounds available for use as alternatives to Cu-based fungicides. Initial experimental work sought to characterise the environmental availability of Cu-based fungicide residues in vineyard soils from 10 different viticultural regions of Australia. The availability of the Cu was found to be relatively low (< 0.5 % of total Cu in the majority of vineyard soils), and influenced by the total Cu concentration of the soil and soil properties influencing cation exchange processes and capacity for soil to adsorb Cu (i.e. pH, clay, exchangeable K, silt, CaCO3). Published data on total Cu concentrations and new information on concentrations of available Cu in Australian vineyards soils generated by this research were used to indicate exposure concentrations to soil organisms which identified likely risks to soil organisms. The second phase of this project involved the incubation of ‘real’ field collected soils from three different regions of Australia to determine the ecotoxicological effects of long-term exposure to Cu-based fungicide residues to enzyme activities (as sensitive indicators of microbial activity). At the concentrations of Cu present in the studied soils (i.e. 90 % less than 115 mg/kg total Cu) the results suggested that enzyme activities were being driven predominately by physical-chemical soil properties (i.e. organic C, pH) with little evidence of adverse effects due to Cu. However, there were some indications that Cu was disrupting microbial mediated phosphorus processes in the soils. Whilst not appearing to directly affect soil microbial activity it was thought that this persistent Cu stress may affect the susceptibility of microbial activity to secondary stressors such as an additional heat stress. Experimental work to assess this found that at the concentrations of Cu typically reported in Australian vineyard soils, Cu stress is unlikely to cause lasting alterations to the susceptibility of phosphomonoesterase and urease following a heat disturbance. Globally there are societal and regulatory pressures to move towards restrictions on Cu-based fungicide use. As such, there is likely to be an increase in the use of alternative synthetic organic fungicide compounds. Laboratory experiments suggested that the alternative fungicides, captan and trifloxystrobin, are likely to pose a lower long-term risk to soil microbial activity compared with Cu-based fungicides. However, results from a study in a horticultural production catchment suggest that the use of synthetic organic fungicide compounds may pose a risk to aquatic ecosystems. Although, comparative analysis suggests that on the whole, the use of pthlamide, dithiocarbamate, strobilurin and triazole fungicides over Cu-based fungicides may result in decreased long-term risks to terrestrial and aquatic ecosystems. This project has generated new information on the environmental risks of Cu-based and alternative fungicide compounds which viticultural industries in Australia can use for environmental reporting, benchmarking against viticultural/wine industries in other countries, and formulating evidence-based policy decisions on the future management of Cu-based fungicides. On the whole the evidence suggests that Cu-based fungicide residues are currently unlikely to pose a significant risk to soil organisms in Australian vineyard soils. However, there are indicators that continued applications of Cu-based fungicides may well have implications on the use of impacted land for sustainable agricultural production. Regardless of the actual risks posed there remain societal and regulatory pressures to introduce restrictions on the use of Cu-based fungicides. The challenge is now for the industry to formulate appropriate plans to reduce the risks associated with Cu-based fungicide use, and this should be the focus of future research and development. This should expand on the relative risk assessment of alternative fungicide compounds commenced in this project

Environmental risks of fungicides used in horticultural production systems

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Use of reference soils in determinations of 0.01 m calcium chloride available metals

There are few readily available standard reference soils for which 0.01 M calcium chloride (CaCl) soil extraction available metals data are available. This study assessed the ease with which new available metals data could be generated for reference soils. Data on 0.01 M CaCl available elements for four reference soils from the Wageningen Evaluating Programs for Analytical Laboratories and three reference soils from the Australasian Soil and Plant Analysis Council proficiency testing program are presented. It is difficult to generate new 0.01 M CaCl available metal values for standard reference soils, because trace element concentrations are low and measurements have relatively high variability. We suggest that laboratories can use reference soils as quality control samples in the analysis of 0.01 M CaCl available metals by reporting recoveries for major elements (e.g., potassium [K], magnesium [Mg], and sodium [Na], for which reference values are of high reliability) to provide assurance of acceptable extraction efficiency

Influence of Increasing Soil Copper Concentration on the Susceptibility of Phosphomonoesterase and Urease to Heat Disturbance

Long-term exposure to elevated copper (Cu) concentrations may affect the ability of soil microbes to withstand additional transient disturbances, such as heat. Bulk surface soil samples collected from three south east Australian locations were spiked with a series of Cu concentrations ranging from 0 to 1,000\ua0mg/kg. To determine the effect of increasing soil Cu concentrations on phosphomonoesterase and urease activity following a simulated heat disturbance, aliquots of each of the Cu-treated soils were exposed to 60\ua0°C for 24\ua0h (perturbed group), and phosphomonoesterase and urease activity measured after 1, 2 and 7\ua0days. Without heat disturbance, the Cu concentration causing significant inhibition of enzyme activity ranged from 50 to >1,000\ua0mg/kg added Cu for phosphomonoesterase activity and 500 to > 1,000\ua0mg/kg added Cu for urease activity. The Cu pre-exposure concentration increased the susceptibility of phosphomonoesterase activity but not urease activity to the heat disturbance. However, this did not follow a clear dose-response relationship and the effects were not lasting. The response differed according to soil type, with decreased resistance to heat found at concentrations ranging from 100\ua0mg/kg added Cu in the silty loam soil to >1,000\ua0mg/kg added Cu in the clay loam soil. The results from this study suggest that, at the concentrations of Cu typically reported in agricultural soils, Cu stress is unlikely to cause lasting alterations to the susceptibility of soil enzymes to a single moderate heat disturbance

Industry Wide Risk Assessment: A Case Study of Cu in Australian Vineyard Soils

There are concerns over the environmental risks posed by Cu-based fungicide use, and there is community and regulatory pressure on viticultural industries to restrict the use of Cu-based fungicides. This study assesses the relative environmental risks posed by Cu-based and alternative synthetic organic fungicide compounds used in Australian vineyards, giving particular consideration to their adverse effects on soil microbial activity and how risks vary across different viticultural regions. The study was guided by key steps in the ecological risk assessment framework to analyse the risks of Cu-based fungicides towards soil organisms and involved four key steps: (1) problem formulation, (2) analysis (characterise exposure and effects), (3) risk characterisation and (4) risk assessment. There is evidence of a build-up of Cu-based fungicide residues in Australian vineyard soils, although this has occurred over many years, thus allowing the availability of Cu in the soil to be attenuated over time due to aging processes. On the whole, it appears that Cu-based fungicide residues are currently unlikely to pose a significant risk to soil organisms in Australian vineyard soils. However, there are indicators that continued applications of Cu-based fungicides may well have implications on the use of impacted land for sustainable agricultural production. Further detailed studies are required to enable a more definitive characterisation of the risks posed by Cu-based fungicide residues, such as establishing a clearer link between the laboratory and agricultural settings, investigating effects on other indicators of microbial activity and biodiversity and understanding the resilience of soil microbes to additional stressors. The challenge for agricultural industries and governments, both in Australia and globally, is to formulate appropriate plans to reduce the risks associated with Cu-based fungicide use. Further research is required to consider the relative risks of a wide range of alternative fungicide compounds to ensure that they pose a lower environmental risk than the Cu-based fungicides they may replace

Effects of copper fungicide residues on the microbial function of vineyard soils

The use of copper-based fungicides leads to an accumulation of copper (Cu) in vineyard soils, potentially causing adverse effects to the microbial function and fertility of the soil. This study used a soil microcosm approach to assess the effects of Cu accumulation on microbial function in vineyard soils. Surface soil samples were collected from 10 vineyards and a number of un-impacted reference sites in each of three different viticultural regions of Australia. The field-collected soils were transferred to microcosms and maintained for up to 93 days in the laboratory at 20-22 °C and 60 % of their maximum water-holding capacity. The microbial function of the soils was indicated by measuring phosphomonoesterase, arylsulfatase, urease, and phenol oxidase activities. In general, the vineyard soils had greater concentrations of Cu and lower enzyme activities than in the reference soils, although a weak negative relationship between Cu and enzyme activity could only be found for phosphomonoesterase activity. The results show that soil physical-chemical properties (i. e., organic carbon, pH) are greater determinants of soil enzyme activity than increased soil Cu concentration at the Cu concentrations present in vineyard soils