Coonawarra on the March

Margaret River stole a march on Coonawarra in the past decade for the title of Australia's best cabernet region. There's more 'buzz' for Margaret River among wine-lovers in recent years. Coonawarra hasn't put up much of a fight. The challenge has gone unanswered. But, after a week in Coonawarra recently, I'm convinced Coonawarra is changing and we're about to see a quantum leap in quality.

Coonawarra is synonymous with cabernet sauvignon. But too many wines of recent memory have been thin and tart, herbaceous and under-ripe, or else over-oaked. A puzzling feature of Coonawarra cabernet in the '80s and '90s was that it often tasted herbaceous and overripe at the same time. Green flavours and astringent tannins were found in the same glass as stewy, overripe or 'dead-fruit' characters – a lack of vibrancy that comes when grapes are harvested too late. After my recent trip I've begun to understand this syndrome.

Let's wind the clock back a few years first. Because of its isolation and lack of a labour force, Coonawarra has, during my 20-odd years as an observer, been big on mechanisation. Mechanical pruning and harvesting were normal, and minimal pruning was an extreme version of mechanical pruning: a tractor with a circular saw would run along the vine rows and saw off just the tips of the shoots. That was all the pruning the vines got. Result: after many years of this treatment, the vines look like hedges, with a tangled mass of dead and diseased wood in the centre. But that's changing. Coonawarra has a new labour source. Migrants, especially Cambodians and Afghanis, are bussed in to prune and pick and do other manual vineyard work.

Vineyards are being 're-constructed' on a large scale. Wynns has done 220 hectares so far. They chop out all the old wood and spur-prune the vines properly. They look neater -- more like traditionally hand-pruned vines. And it improves the fruit quality.

Now let's go back to the overripe/underripe syndrome. A lot of it's to do with uneven ripening within vineyard blocks – which in turn can be traced to soil variations. Vineyard managers have hit upon near-infrared aerial photography. The pictures show areas of high, low and moderate vegetation density within vineyards, represented by coloured areas on a map. At a glance, the viticulturist can see which areas of a vineyard are low vigour, high vigour or somewhere between. According to Yalumba winemaker Peter Gambetta, the difference in ripening dates between low and high vigour vines can be as much as two weeks.

In the past, a machine harvester would have picked the entire block in a couple of hours. All the grapes, whether underripe, over-ripe or perfectly ripe, went into the same bins, the same fermenters and the same bottles. No-one really knew that there were variations in the vineyards because no-one had thought to look closely.

But now, it's understood that different soils lead to areas of different vigour and the higher the vigour, the more ripening is delayed. So, vineyards are being selectively harvested and the result is more even ripeness, and much better wine.

Near-infrared is being used in tandem with harvester-mounted yield recorders, which map vineyards by measuring the quantity of grapes pouring into the harvester bin, for every section of the vineyard.

Also, the bigger companies, especially Wynns, are using bud dissection to predict future yields. Because next season's bunches are already inside this season's buds – in microscopic miniature – it's possible to analyse buds and get a better idea of what the crop load will be next year, and to plan for that. Wynns' Allen Jenkins says that in one season they dissected no less than 7,440 buds. This led to 440 hectares of vines being bunch-thinned, which means bunches were snipped from vines to decrease crop yield. This in turn meant better quality fruit, because the remaining bunches had a better chance of ripening properly. Some of the vines had their crop reduced from a whopping 15 tonnes per hectare to eight; others were cut from eight to six, which is into the five-to-six tonnes per hectare range required for A-grade grapes. Of course, the weather always reserves the right to intervene, and mess up the best-laid yield prediction plans. But the more information the vineyard manager has, the more chance of harvesting top-quality grapes. "Yields can vary between 2.5 and eight tonnes per hectare from year to year on the same block of vines," says Jenkins. "So yield prediction is very important."

I expect we'll be starting to see, and taste, the results of these advances in Coonawarra reds in the next year or two. Watch out Margaret River!