I saw this article by Dr. Richard Smart (credentials at the end of the
article) in the new issue of Wine Business Monthly and thought it was
interesting and provocative.

Tom S

"THE PREDOMINANT MYTH
Surely the predominant myth of the wine industry is that high yields result
in low wine quality-it is the basis of European mythology that has become
legislated under appellation schemes. And these ideas are also widespread in
the wine industry of the New World.

Imagine the opening of a new T-shirt shop. The grand opening is fast
approaching, and suddenly the owner takes a third of the stock and throws it
in the trash can. Why do this? Consider the idea that reducing overall stock
will make the remaining stock more desirable to customers, perhaps giving an
impression of exclusiveness and higher quality. You will surely say, "How
stupid is that?" Yet for those of you out there who thin crop on your
grapevines, how much factual basis do you have that discarding a proportion
of the fruit will make the remainder better? Who are you trying to convince?
Do you rely on a belief system?

This idea has so much currency that I have heard some grape growers "reverse
boasting" about how much fruit they put on the vineyard floor. Enologists,
almost universally, believe that high yields will lead to reduced wine
quality. But, is it true?

If it is true, we must concede that we are part of an inefficient sector,
forever destined to low productivity. The other side of the coin is even
more economically distasteful: that we are discarding some of our production
in the mistaken belief that this will improve quality, for which we will be
rewarded.

For what other foods and beverages do we hold the same viewpoint? None, so
far as I can see. Who drinks beer only from low-yielding barley or hops? Who
demands steak from malnourished, skinny animals? Which wine critic at dinner
will ask for small potatoes? Why are grapevines singled out for a stressful
life among plants and animals, on which our agriculture is based? Because of
mythology, that is why.

WHY DOES THE MYTH EXIST?
I have observed in many wine regions that low-vigor vineyards have the best
reputation for quality (this is admittedly more common for red than white
table wines). In some instances, especially in Europe, these vineyard
estates produce distinctive wines in most seasons, leading us to the
conclusion that this feature has much to do with the site and less to do
with the seasonal weather.

Low vigor vineyards have several common features throughout the world. Water
stress is the common cause of reduced vigor. Shoot growth is inhibited,
typically showing before bloom. Internodes are not so long nor diameter so
wide, and main leaves are less than normal. Lateral shoots develop poorly if
at all. The canopy is typically open, with good leaf and fruit exposure.
Shoot tip growth slows before veraison, and growth terminates soon after.
Provided stress levels are not high, the vines will produce a moderate yield
that will ripen before that of high vigor vines.

Note clearly that I am not arguing for maximum stress, which will cause
substantial reductions in. yield and loss of active leaf area. I am
describing the typical course of developing water stress that is found in
Mediterranean climates, with no or limited irrigation. Soil depth and
water-holding capacity are all important.

Is low yield the cause of the quality benefits? Or maybe it is a vigor
effect. Perhaps the patterns of shoot growth are also important. And the
open canopy can be a contributor as well. I believe all of these points are
important, and I find it regrettable that the myth has been built up to
consider yield solely.

QUESTIONING THE MYTH
There are many examples that suggest that higher yields do not necessarily
lead to lower quality. The first I'd like to mention relates to a recent
Napa Valley study involving Cabernet Sauvignon ("Sensory attributes of
Cabernet Sauvignon wines made from vines with different crop yield" by D.
Chapman, M. Mathews and J. Guinard, 2004, Am. I. Enol. Vitie., 55: 325-334).

Vines planted in 1995 and grafted to 110R were pruned to six levels, with
between 12 and 48 buds per vine, spaced at 1.8 meters in the row. Yield was
also varied by thinning at veraison to 12 to 96 clusters per vine, in
conjunction with two pruning levels (24 and 48 buds per vine).

The field trials and fermentations were properly replicated, and a sensory
panel trained. As was expected, yield increased as more buds were left at
pruning and with less thinning, producing a range of yields varying from 1.6
to 8.8 tons per acre. The treatments produced wines that differed in aroma
and taste attributes. Wines produced by pruning level showed much more
effect of treatment than did those produced by thinning.

Interestingly, and counterintuitively (and certainly contrary to the myth
under discussion), the low yielding vines, due to severe pruning, produced
more negative wine characters than did high yielding wine. In particular,
fruity aromas were higher as the number of buds per vine and yield
increased. Similarly, low yielding wines were more astringent. Conversely,
low yields were associated with more "veggie" and bell pepper aromas. Also
interesting was the response to cluster thinning. There were no associations
between aroma and yield although low yields were again more astringent.

So, low yielding wines were of "lower quality", being more astringent and
more veggie but only when yield differences were established by pruning.
Cluster thinning had little effect on aroma attributes despite having a
greater effect on yield. However, it was important to note that the effects
on wine sensory evaluation were much less than those on yield.

What is patently obvious is that this excellent study was flawed by lack of
vineyard measurement. There were no assessments of pruning weight, mean cane
weight or of canopy microclimate. So the authors were left in a quandary to
explain their results. My guess is that the severe pruning stimulated
vegetative growth and methoxypyrazine production (a cause of veggie
characters).

There is no doubt, however, that yield was not the determinant of wine
sensory features. Method of yield control was more important than final
yield in affecting sensory features. And, significantly, higher yielding
vines produced wines with more positive attributes and fewer negative ones.
So much for the myth.

The second experience relates to a Cabernet Franc experiment that I
conducted in Hamilton, New Zealand in the 1980s (see "Canopy management to
improve grape yield and wine quality principles and practices", Smart, R. et
al. S. Afr. I. Enol. Vitie., 11,3-17).

This location has a cool climate similar to northern Oregon: the soil was
quite deep and fertile, and summer rainfall was significant. Vines on 1202C
and AxR1 were vigorous and trained to a range of training systems, with two
row spacings at six feet and 12 feet. Again, the trial was replicated as was
the winemaking from each plot and the sensory evaluation. Local winemakers
were used for sensory evaluation, but they were screened (without their
knowledge) as to their ability to reliably assess the wines.

Vertical shoot positioning (VSP) training produced shaded canopies and lower
yields, which is no surprise. (VSP is not suited to high capacity soils and
high vigor. Both yield and quality can be inhibited by shaded canopies.)
Other trellis treatments created a greater canopy surface area and a less
shaded canopy, and so yield was also increased. When yield was compared to a
wine's sensory score, a positive correlation was found. That is, the higher
the yield the better the wine as assessed by wine judges. This was because
the shading of the high vigor, lower yielding VSP vines reduced the color
and aroma of wines. This was improved by better balanced, higher yielding
vines trained to a more appropriate trellis. So much for the myth.

The third experience has to do with the 2005 harvest at Tamar Ridge
Vineyards in Tasmania, Australia. We used aerial infrared photography (NDVI,
Normalized Difference Vegetation Index) to create vigor maps of the
vineyard. We found part of our Sauvignon Blanc vineyard to be of
substantially lower vigor due to water and nitrogen stress. The yield was
lower as would be expected, but we also found that the fruit at the point of
harvest lacked varietal definition. Nearby, adjacent vines in deeper soil
were more vigorous, with higher yield but more typical flavor. We
differentially harvested the block, and the higher yielding portion produced
the better wine quality as assessed at the post vintage tasting.

Consequently, Tamar Ridge has recently out pointed many well known brands
from Australia and New Zealand, and has been awarded one of only two gold
medals at the 2005 Perth Wine Show for its 2005 Sauvignon Blanc. This
winning wine was made from high vigor vines, using differential harvesting
as described above.

These are just a few examples among many to suggest that higher yields do
not necessarily lead to lower quality; in fact, the converse might be true.
They suggest that the means of regulating crop pruning compared to cluster
thinning could be more important than yield itself. If you are cluster
thinning at veraison, you should worry that you might be throwing money
away.
So much for the myth."

Dr. Richard Smart, the "flying vine-doctor", is an Australian viticulture
consultant, with clients in 22 countries worldwide. He is an expert on
canopy and other vineyard management to improve wine quality. He conducts
seminars and educational wine tours to regions around the world. Dr. Smart
visits North America frequently for consulting and may be contacted at
vinedoctor@ compuserve.com. For more information, visit www.smartvit.com.au.

> Imagine the opening of a new T-shirt shop. The grand opening is fast
> approaching, and suddenly the owner takes a third of the stock and throws it
> in the trash can. Why do this? Consider the idea that reducing overall stock
> will make the remaining stock more desirable to customers, perhaps giving an
> impression of exclusiveness and higher quality.

I don't know whether the predominant thinking about yield and quality is
true or not, but the snip above is not any kind of parallel. That's
more like throwing half your wine away to make the rest more valuable
(something that does work for collectable coins).

The idea is that pruning lets the remaining grapes have a better chance
at the nutrients and such that make them good. I can't really imagine
T-shirts having this quality (and if they did, I wouldn't want to wear
them!) Perhaps more in line with the topic would be throwing out the
bottom half of your ink, because that's where the sludge is. The
T-shirts made with the top half would be higher quality. Or somesuch.

> Who
> demands steak from malnourished, skinny animals? Which wine critic at dinner
> will ask for small potatoes?

Uh.... how about the trend for baby vegetables and veal? Not quite the
same, but not so different either.

Jose
--
Money: what you need when you run out of brains.
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