Yield and quality, and epistemology (on Palate Press)

An enormous lot has been said about the relationship, or lack thereof, between grape yield and wine quality. So why is my October piece for Palate Press about whether higher yields mean lower quality?

1. My Palate Press colleague W. Blake Gray took an interesting economic tack on the problem a few months ago, reminding me that I wanted to revisit what we know via the scientific approach.

2. I’ve been more than a bit obsessed with the contacts (and conflicts, and congruencies) between anecdotal and scientific knowledge of late. The yield-quality problem is a fantastic case of the scientific evidence we have strongly suggesting one position (higher yields ≠ lower quality) while some peoples’ experience suggests that more may be going on than science has yet to document.

3. It’s a perennial question for a reason (or two): it’s interesting, and it’s important. And revisiting interesting and important things is worthwhile.

4. Richard Smart wrote an article for Wine Business Monthly back in 2004 proving, via contrary anecdotes, that higher yields don’t always mean lower quality, and that the principle isn’t true from a scientific perspective. He also implied that anyone who thought that myth had a place in winemaking was 1) a moron, and 2) unscientific, and that riled my epistemological feathers enough to want to write on the same topic from a different (better)* perspective. More on myths another day.

The short version: the oft-cited yield-quality relationship is more about correlation than causation particularly from the perspective of the scientific evidence, but whenever we’re talking quality things get fuzzy (and social) and our perceptions about wine quality involve more than just measurable scientific variables.

The long version is here. 


* Yes. I’ve just compared myself to a highly-accomplished viticultural scientist and found him wanting. Dr. Richard Smart is a marvelous scientist. He also, by this single account at least (I’ve not tracked down more examples), has ideas about which forms of knowledge-making are valid that I find deeply misguided.

8 thoughts on “Yield and quality, and epistemology (on Palate Press)

  1. Some good work has been done in Marlborough on SB crop levels and quality involving what appear to be scientifically “appropriate” organoleptic appraisals.
    They’ve shown crop does not influence quality at pre-determined physiological harvest parameters.
    As a Winemaker with vast local experience I’ve found that hard to believe.
    I’m currently keeping those thoughts apart.

    • Aside from any causal connection between yield and quality, it seems that there would be an economic one. That is, high yield and high quality would delight vignerons, and they might be able to survive on low yield/high quality or high yield/low quality, but certainly not on low yield/low quality. Thus the starting position is slanted to the perception of an inverse relationship.

      • John, I agree wholeheartedly, and I think that the dynamic you outlined is made more complicated by our perceptions that things which are a) rare or in low supply, b) deliberately reduced when they didn’t have to be, and c) are more expensive to produce are better. I haven’t looked — I should — but I suspect that the Journal of Wine Economics has something (or lots of things) to say about that relationship and perception.

    • I’ve been following the S.B. data and have wondered how much of the work done on that variety translates to other varieties and to other settings. I think that what you’ve pointed out is key: in addition to the scientific data, which gives us one picture, we need to consider extensive grower experience in putting together our explanations and practices.

  2. Read and enjoyed your long version, and there are a couple of picky factual errors:
    “Removing leaves early in the season can reduce the number of clusters a vine sets out to produce, but also lets more sunlight hit ripening grapes – lower yields, higher quality.”

    Leaf removal, whether mechanical or manual, does not remove grape clusters. Shoot thinning (which may be what you are talking about) will remove clusters with the shoot and improve light interception. The other error: Mechanical cluster thinning “where the tractor beats off unripe clusters” (not really a quote, a paraphrase) is not something that high-end wineries are likely to do. They are more likely to manually thin clusters either early, or at veraison (green harvest), where some remove lagging clusters.
    Mechanical thinning is used to reduce crop in New York Concord vineyards (juice grapes), but it would in no way selectively remove less ripe clusters, in fact the reverse would be true: riper=easier to beat off.

    I recall a Napa producer who told us about a vineyard that traversed a slope and valley floor. They put the valley fruit into low-priced and bulk wine, and the slope fruit into their high priced stuff. However, after they removed every other vine and extended cordons (providing more space to balance the higher vigor), they were able to put the valley fruit into the premium blend. So the ‘balance part’ = maximizing fruit quality by proper spacing of shoots, and allowing enough space for each vine. Operative variable: Canopy density: amount of canopy/leaf area per unit of row.

    • Thanks, Tim. I’m actually talking about early leaf plucking, not shoot thinning to remove clusters; that may still be wrong, but either my sources are wrong or I’ve misinterpreted them. Mechanical thinning is used widely in New Zealand (fewer Mexican farm laborers, for one), though I didn’t mean to suggest that it was a common practice among high-end wineries at all; apologies if I did.

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