Comparing organic, biodynamic and conventional vineyard management Chris Penfold, Luke Johnston, Melissa Brown, Petra Marschner, Sue Bastian and Cassandra Collins
Introduction ORGANIC AND BIODYNAMIC viticultural practices have received much attention worldwide, particularly by premium grapegrowers. An increase in the number of growers in Australia converting to organic and in particular biodynamic vineyard management practices has occurred over the past 10 years. One such grower is Melissa Brown, viticulturist at Gemtree Vineyards based at McLaren Flat. In 2008 she collaborated with researchers at the University of Adelaide to establish a replicated field trial to compare organic and biodynamic vineyard management with both low and high-input conventional systems at Gemtree. The first stage of the trial focused on assessing changes in soil properties, vine growth and wine quality over the threeyear conversion period needed to gain both organic or biodynamic certification and formed part of Luke Johnston’s PhD studies. This large scale trial is on a 10ha block of Cabernet Sauvignon and also incorporates the addition of compost (applied undervine) to each of the management systems to determine if compost is a major point of difference between the management systems. In 2011, the trial received funding from the GWRDC to continue the project until
April 2013 – Issue 591
2014, to assess the longer term effects of these management systems.
Summary of three-year period Measurements of soil properties, vine performance, berry composition and wine quality were used to compare management treatments. Compost had a greater effect on soil properties, while there were no consistent differences in all soil measurements between management systems. Compost increased soil organic carbon, cumulative respiration, microbial biomass carbon, available nitrogen and phosphorous (regardless of the system). Over the duration of the conversion period, management system had no effect on soil organic carbon, microbial biomass carbon or chemical properties. Cumulative respiration was higher in organic and biodynamic treatments when undervine
Undervine management: conventional herbicide system.
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weeds were actively growing compared with conventionally managed vines, which remained bare due to herbicides being used. However, when undervine weeds were removed via cultivation (to limit competition with the vine for nutrients and water) all management systems had the same cumulative respiration levels. No consistent effect of management system on vine and fruit quality measures was seen in results from the first two seasons. However, in the third season vine growth and yield were lower for organic and biodynamic treatments compared with conventional treatments. Total phenolic levels were also higher in the biodynamically managed vines compared with other management systems. Wines produced in seasons two and three from the trial were assessed by an expert panel of winemakers from
Undervine management: organic system.
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