The delicate art of balancing wine grape quality with higher yield is likely to become easier for grape producers with the advent of precision farming techniques in the vineyard.
Research by CSIRO, Southcorp Wines Pty Ltd and the Viticulture CRC in the Coonawarra has shown that grape yield and fruit quality can vary widely within quite small areas of vines - the result, at least in part, of changes in soil type, nutrient supply, depth and moisture.
As a result, some parts of a grape block being managed conventionally may be highly profitable while others, only metres away, may be making a substantial loss, says CSIRO Land & Water researcher Dr Rob Bramley.
Precision viticulture offers the grape producer a low-cost way to overcome this, by fine-tuning the management of particular areas of the vineyard to achieve the desired combination of quality and yield.
This could be vital to ensure the future competitiveness and sustainability of Australia's $800 million wine export trade, says Southcorp's Dr Tony Proffitt.
"The aim of our research is to establish to what extent yield and quality are influenced by manageable variations in soil properties," Dr Bramley told an International symposium on cool climate viticulture in Melbourne today.
"The industry's conventional wisdom is that higher grape yields mean lower quality. I have a feeling this may not always be the case: subtle changes in fruit quality may well be influenced by subtle variations in soil chemistry and nutrient availability - which can be controlled by careful management.
"In other words, there may be a good opportunity to optimise both yield and quality to achieve the best financial outcome for the producer or the best environmental solution, if that is the goal."
Early results from the Coonawarra experiment suggest this is the case. The researchers have found evidence of a significant variation in yield, crop maturity and key quality indicators such as colour and acidity according to the nature of the soil that the vines are growing on.
"These early findings encourage us to believe that fruit quality is a more controllable factor that many people assume."
Dr Bramley says that many grape producers would like to be able to have more control over their production system.
He and Southcorp Wines' Dr Proffitt have identified the main advantages of precision management in the vineyard as:
. more efficient use of inputs such as fertiliser, sprays, water etc.
. ability to show that best-practice has been used in grape production
. improved quality control, leading to segregation of crops at harvest
. harvesting according to quality specifications
. improved harvest scheduling
. more precise sampling of vineyards to aid management decisions
. an improved basis for paying grape growers
. improved vineyard design.
The cost of precision viticulture is not as great as many might imagine, Dr Bramley and Dr Proffitt say. While it requires the purchase of a yield monitor using satellite navigation (about $26,000) and some diagnostic analysis of soil and plants, over five years the total costs should work out at around $4 to $5 per tonne of grapes.
"We feel precision viticulture offers a low cost means to improve grape and wine production, with downstream benefits which will ensure the continued growth and competitiveness of the industry," Dr Proffitt says.
"This is very new technology to our industry, and not many people are aware of all it has to offer..." he says.
"It's one way to ensure the Australian wine industry remains both competitive and sustainable a long way into the future."