Remote sensing Smart move

With vintage now under way in Tasmania, you needn't look far to find growers who say that choosing when and where to pick are the most important decisions they'll reach over the next couple of weeks.

Few choices are made without some sense of anxiety.

Good decision-making requires accurate information about a whole range of vineyard factors - and reliable, objective measurements can be very hard to obtain.

Internationally recognised viticulturist and researcher Dr Richard Smart understands the dilemmas faced by wine producers. There's more to grape growing than meets the eye.

He's just spent the past fortnight helping to formulate a vintage plan for Gunns-owned Tamar Ridge Wines. The final proposal sounds more like science fiction than science fact. Essentially, it links years of local knowledge drawn from the vineyard team of Paul Townsend, and Dorothy and Michael Humphreys - and from winemaker Michael Fogarty - with raw data obtained barely a fortnight ago from an advanced technology known as remote sensing.

According to the vine doctor, remote sensing was first used in viticulture in the 1980s. That drew on 'spy in the sky' images taken by satellites orbiting the earth. These days, the imaging is done during a simple vineyard fly-over by an aeroplane carrying state of the art equipment designed for infrared digital photography.

Plant leaves absorb certain wavelengths of light and reflect others. Tasmanian company Serve-Ag has put that principle to use in developing special computer software that can create coloured maps with a range of vegetation indices from the images taken during vineyards flights. These have a strong correlation with vine health and vigour, Smart says.

Put simply, they point out what's going on among the shoots and leaves of a vineyard. They can show where leaf canopies are too thin and grape bunches are over-exposed to sunlight, as well as places where canopies are too dense and the fruit is heavily shaded.

"On the photos we obtained, the data is mapped and divided into five classes according to vigour, and there's a colour code for each," he explains.

"Areas of the vineyard that have a weak canopy or none at all show up in blue, while sections that have a very dense or vigorous canopy are represented in red."

Each of the maps he has in his hands today is clearly outlined by thin blue shading representing the outer perimeter of Kayena's vineyard rows. That reflects the widespread damage that occurred there on February 2nd. Winds in excess of 100kmh battered this part of the Tamar, cutting power to 30,000 homes in the State's north and northeast.

"If it wasn't for that storm, our vines would be looking magnificent," he adds.

Smart says vine vigour can be a major problem for vineyards. Too much results in fruit shading that compromises colour and berry ripeness. It can also have a big effect on budding and fruit set, and creates microclimates that encourage unwanted diseases like botrytis.

Remote sensing allows growers to see whether they need to make changes to irrigation levels, modify fertiliser applications, or prune vines more effectively to maximise production and fruit quality.

There's a pay-off for winemakers, too. It can help growers identify and pick separately vineyard areas that are most likely to deliver the type of fruit and wine a maker is aiming to produce. This year's vintage plan for Pinot Noir grown at Kayena has included classifying each vineyard or vineyard block as Reserve, or Tamar Ridge A or B, depending on vine uniformity and vigour.

"Rather than working across a whole vineyard - as we've done in the past - we'll use the aerial photos to carry out sampling and differential harvesting across certain strata within a vineyard," Smart explains.

"That might seem a small step forwards for grape growers, but it'll mean a giant leap in wine quality for consumers." 

Always thinking ahead, Smart has other plans he intends to address in the near future.

"We did a bit of work on leaf health last year towards the end of the season, and the results were very interesting," he notes. 

"We found that where the leaves were healthiest towards harvest, those blocks performed much better than others in terms of wine quality. That factor seems to have been more important than yield or other parameters such as the type of clone or date of harvest.

"We're still not sure what caused that outcome. There's obviously something going on we don't understand. We're coming to the conclusion that late season leaf health is more important than we first thought at the time. I'd say soil nutrition and soil water management are the important issues - perhaps along with other factors - so it's worthy of further study."

First published 30 March 2005: The Examiner