Going organic in viticulture: A case-study comparison in Clare Valley, South Australia

Long-term studies of organic and conventional viticulture are rare, and there has been little published comparison of the two systems in Australia. This study compares and contrasts yields, grape quality, grape prices, variable costs, worker benefits, soil carbon and biodiversity of organic and conventional viticultural production in Penfolds Clare Valley Estate, South Australia, from the 1990s to the late 2000s. Comparisons are made between overall farming systems, red and white grape varieties and individual grape varieties. Evidence over a number of years was found for: (1) an overall yield penalty per hectare for organic blocks of around 10 per cent but no yield penalty between similar grape varieties; (2) an overall cost penalty per hectare of 10 per cent for organic blocks, owing to higher costs in areas such as soil management and pest and disease; and (3) an overall higher grade quality (and higher prices paid) for organic red grape varieties but a lower overall grade quality (and lower prices paid) for white grape varieties. There was limited evidence from one year to suggest that there were higher soil arthropod and mite populations in the organic blocks, but no differences were found in soil organic carbon between systems. In addition, there was evidence of positive externality influences from the presence of organic farming on the estate on surrounding conventional management.