Friday, March 03, 2006

Yields & quality

The following quote appeared a few months ago in Wine Business Monthly, in an article about vineyard yields and the resulting wine quality by Richard Smart:

"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. ......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?..."

One could kill the whole conversation by mentioning that last year in the Fresno area yields were 13 tons/acre, while in California's North Coast the average was around 5 tons/acre.
Looking at the quality from the two areas and average $$/ton of fruit would be plenty of ammo to prove the "low yield" myth. So enough said, right?

Well, no'd have to discount the large differences in Fresno and the North Coast climate before you could make such a statement, so it'd never be an "apple to apple" comparison. But Mr. Smart has what amounts to nuclear warheads in his arsenal: pruning and yield trials conducted in Napa Valley...trials which appear to poke a hole in the "low yield = high quality" maxim.

Intellectually, it stands to reason that there is some maximum amount of fruit that any one vine can bring to maturity from a quality standpoint. Certainly each area will have some upper limit on crop size which will produce the best wines - and that limit would depend somewhat on trellis system, varietal, rootstock, vineyard aspect, and weather for a particular harvest. Even so, Mr. Smart seems to have evidence that it may not be the case that lower is always better, and while not suggesting overcropping either - asks whether some of the hype in relation to amout of fruit dropped before harvest might be driven by the public perception that less is good.

Historically, Roman authors noted that some of the highest yield vineyards were delivering ~19 tons/acre, while "...first class vineyards produced a hundred amphorae to the iugerum..." in the De Re Rustica (~6.5 tons/acre if my math is correct). It should also be noted that they were discussing financial viability of vineyards, in which more yield is universally better. Sadly they didn't note what those resulting wines were like quality-wise, with the exception of the note about "first-class vineyards", and they ranged over much of the empire in their examples - so again it wasn't an apple-to-apple comparison.

But they also noted that even then people "pick out the very worst section of their lands, as though such ground alone were particularly fit for [grapevines] because incapable of producing anything else." (De Re Rustica, III, 257).
Was this the begining of the myth that grapes must suffer? And is it linked to low yields because our ancestors planted grapes in crappy areas that wouldn't support anything else, and had poor results as far as fertility was concerned?

Mr. Smart has a few other choice observations, like...

"[t]his 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.

Perhaps we should be looking at claims of "low-yield" a little differently...
I know I will...


Anonymous Mithrandir said...

Fascinating. It's good to see people actually approaching viticulture scientifically. It's odd that they don't seem to mention pre-fertilization cluster thinning. It's a technique that I've heard very good things about.

Premise: the magic happens in the leaves.

Hypothesis: crop yeild is a poor indicator of quality. The ratio of leaves to clusters is a good indicator of crop quality.

Test: measure yeild per acre for various crop control strategies, but also measure pruning weight in the fall. Attempt to corellate the ratio of pruning weight to crop yeild with quality. Use a trellis system with good sun exposure for the canopy.

Makes me wish I had a lab, err, vineyard of my own.

March 03, 2006 12:19 PM  
Blogger St. Vini said...

Nothing like actually looking for reproducible results via experimentation, eh?

There may be hope for the human race yet...or at least it's viticulture.

Thanks for the comment,

March 04, 2006 6:13 PM  
Blogger JeffH said...

A similar dreamscape involves people of the low-yield faith increasing the number of plants per acre to ridiculous numbers (4000-5000 plants per acre). This allows them to boast they are harvesting only one or two bunches per plant. I heard that one vineyard combined high plant numbers with 1 ton per acre yield. I ran some numbers and was highly amused to realize that at such a high a plant count and low per acre yields they will be picking only one bunch every second plant and removing all fruit from the alternate plant!

March 12, 2007 1:01 AM  
Blogger St. Vini said...

I know of vineyards in the EU which are planted at that density (4~5k/acre), but the owners aren't trying to drop the yields that far...

You're right though, why have the extra plants if you're not utilizing them?


March 13, 2007 6:24 AM  

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