Soil Chemistry and Wine Flavor

I am organising a tasting of wines grown in volcanic soils (in southern Italy), and am having trouble finding any scientific support for the idea that soil chemistry can affect wine flavor. As a wine taster, this makes no sense; can anyone shed light on this?

A lot more than soil chemistry is responsible for the flavors in wine. Soil chemistry has a much greater effect on how the vines grow than on the flavor of the berries. The weather and vineyard practices, such as crop thinning, canopy management, spray programs to control mildews and pests, and drainage issues would effect the final flavors in the berries more than the soil content. Grapes do not have very high soil nutrient requirements and grow better in well drained soils. Here are two links about soil that might be of interest: http://www.extension.org/pages/31517/monitoring-grapevine-nutrition; http://www.extension.org/pages/55689/soil-sampling-in-vineyards.
EDIT:

As a wine taster, this makes no sense...

If you grew Roma tomatoes in your garden in Oakland and made a pot of sauce, would it be different than if you made it from Roma tomatoes grown in your garden in Piedmont, and if so, would you attribute it to the soil?

uh.. isn't this at least partly the terroir debate????

And Howie, if I were fortunate to have a garden in Piemonte, I wouldn't care if they tasted differently.... but they might!!! If only psychologically!

A lot more than soil chemistry is responsible for the flavors in wine. Soil chemistry has a much greater effect on how the vines grow than on the flavor of the berries. The weather and vineyard practices, such as crop thinning, canopy management, spray programs to control mildews and pests, and drainage issues would effect the final flavors in the berries more than the soil content. Grapes do not have very high soil nutrient requirements and grow better in well drained soils. Here are two links about soil that might be of interest: http://www.extension.org/pages/31517/monitoring-grapevine-nutrition; http://www.extension.org/pages/55689/soil-sampling-in-vineyards.
EDIT:

As a wine taster, this makes no sense...

If you grew Roma tomatoes in your garden in Oakland and made a pot of sauce, would it be different than if you made it from Roma tomatoes grown in your garden in Piedmont, and if so, would you attribute it to the soil?

Howie,

I'm not sure if I can ripen Roma here, but Early Girl do pretty well. To answer your tongue-in-cheek question, if everything else was equal, I would be inclined to assume that differences might be due to the variable, yes.

Much of the hard scientific commentary on this topic I've seen appears to be dedicated to debunking the idea that slate can travel up through the plant and end up in the wine, a silly idea which apparently a number of wine writers in unguarded moments have espoused. (Wouldn't some wines then also taste of cow manure?) It doesn't seem to answer the question, for example, 'wines from volcanic soils appear to have some flavor similarities, why might this be true?' There are all kinds of wrinkles here, eg if a vineyard in Napa planted in alluvial soil is irrigated with water from a volcanic formation 600 feet underground, which influence is more important? I'm not looking for a finished answer, just enough background to understand the boundaries of the discussion.

I am... having trouble finding any scientific support for the idea that soil chemistry can affect wine flavor.

I think that's because there isn't any (or much) evidence for it. There is evidence that soil structure plays an indirect role (by controlling water supply to the vine), but AFAIK there's no evidence for the direct influence of soil chemistry on berry flavour at all.

Much of the hard scientific commentary on this topic I've seen appears to be dedicated to debunking the idea that slate can travel up through the plant and end up in the wine, a silly idea which apparently a number of wine writers in unguarded moments have espoused... It doesn't seem to answer the question, for example, 'wines from volcanic soils appear to have some flavor similarities, why might this be true?'

It's certainly unfortunate that so many wine writers (and wine lovers) maintain that slate concept. Clearly, it's far more complicated than mineral uptake resulting directly in "mineral" flavour expression.

One might also question the reality of the statement that a certain soil type imparts a certain flavoru profile as a generalisation; it may be true for particular regions, but that vaidity is again confounded by the other influences (e.g., is it how the rainfall recharge interacts with the volcanic geology in that location which influences the flavour in that certain way, or is it the actual soil/rock minerals themselves that influence, or both?).

There are all kinds of wrinkles here, eg if a vineyard in Napa planted in alluvial soil is irrigated with water from a volcanic formation 600 feet underground, which influence is more important?

The one I really wonder about is the idea that grapes can't express the "terroir" (unique characteristics of the site) without the vines' roots having penetrated rock (seems a particularly common perception in France).

A LOT more scientific research is needed to even begin to understand these issues.

Ben is onto something. Not only chemistry, but physics: solar reflectivity, heat retention, drainage.... they will all be influenced by soil type.

But it is true: wines like those from Etna seem to exhibit the stamp of that volcanic soil.

Does this article help? http://www.wineanorak.com/mechanisms_terroir1.htm

If, as Howie says, the weather and vineyard practices, such as crop thinning, canopy management, spray programs to control mildews and pests, and drainage issues effect the final flavors in the berries more than the soil content, then how is it that year after year Bordeaux tastes like Bordeaux and Cal cab tastes like Cal cab? If one agrees that Bordeaux has a characteristic taste year after year, then I guess one could conjecture, if he accepts Howie's thesis, that if there is any translation from the soil at all, it must be like TCA, in that a tiny amount of these characteristic chemicals stand way out among the much larger array of chemicals that derive from the factors that Howie iterates. It would be silly, I think, to assume the wine management and weather conditions were never the same in Bordeaux and California, so that at least in one instance at least one of the wines from both regions should have tasted exactly the same. This is a rhetorical question, of course, because there are different berry genetics, etc., too.

Or are most people going to insist that there is no characteristic Bordeaux taste, and that any such perception is all psychological? Of course it is all psychological, meaning what we perceive as taste resides in our heads. Our taste buds and olfactory nerves serve as transducers to such arcane substances as 1,1-Dimethyl ethyl 4-methoxyphenol, or simple vanillin, and nerve impulses, very similar to the I’s and O’s that translate HTML to web browsers, carry those impulses to the nucleus accumbens and ventral pallidum and cortical regions of the brain where these core taste impulses are integrated with impulses (which differ from sensory (taste) impulses only mathematically in the pattern of I’s and O’s) of memory and intellect stemming from what we know about the regions or individual properties and romantic notions and whatnot associated with a particular wine we are drinking.

If terroir has little influence on what we perceive psychologically as taste, then if we were to take a chromatographic analysis on the chemicals in a wine originating, say, at Lafite, it would look very similar to a sample taken at Screaming Eagle, if theoretically we could hold all the variables of vineyard management, vinification process and weather constant – which is of course in reality impossible.

My personal and particular intellectual intuition stemming from my knowledge of statistics and what I know about biology and wine tells me that there would certainly be chemicals we could perceive in the wine that were a function of the soil. But of course I cannot make an evidential case based on my intuition. I wonder if there have been any such studies attempting to factor out the variables of vineyard management, vinification process and weather so that it can be determined if any chemicals exist which originate from the soil, and if they can be detected by human sensory and processing apparatus?

If, as Howie says, the weather and vineyard practices, such as crop thinning, canopy management, spray programs to control mildews and pests, and drainage issues effect the final flavors in the berries more than the soil content, then how is it that year after year Bordeaux tastes like Bordeaux and Cal cab tastes like Cal cab?... Or are most people going to insist that there is no characteristic Bordeaux taste, and that any such perception is all psychological?

There is no doubt that soil type affects grape quality, but Oliver's question was whether soil chemistry affects grape flavour and that's a different issue (though soil chemistry certainly influences vines via nutrient availability, as Howie alluded to).

It would be extremely difficult to argue that soil chemistry plays a more significant role in influencing grape flavour than do vineyard practises, soil type or climate.

I certainly see a characteristic Bordeaux taste, and it's doubtless because the climate and geology of Bordeaux vineyards is distinct from those of (most of) California. (Soil chemistry doesn't have to even come into it - the differences in climate and geology are probably enough, though on top of that there are many other potential points of difference anyway.) Having said that, there are certainly Bordeaux wines that can be confused in blind tastings with Californian Cabernet by highly experienced tasters (and they tend to be those whose vineyards are managed and wines are made using similar techniques - as a generalisation - to those commonly adopted for Californian Cabernet).

I wonder if there have been any such studies attempting to factor out the variables of vineyard management, vinification process and weather so that it can be determined if any chemicals exist which originate from the soil, and if they can be detected by human sensory and processing apparatus?

I think one of the main problems is that it's so difficult to isolate/separate the variables.

If, as Howie says, ... then how is it that year after year Bordeaux tastes like Bordeaux and Cal cab tastes like Cal cab?

I think it's more a function of climate (as opposed to weather). Bordeaux is at 45deg N latitude, while Napa is at 38. Cabernet Sauvignon is a grape that requires a long growing season. Bud break in Bordeax is later than Napa and as a result it may just barely ripen in Bordeaux in some years. This is why, in Bordeaux, Cabernet Sauvignon is only grown in certain appellations and is usually blended with earlier ripening grapes like Merlot and Cab Franc. Whereas, in Napa, Cabernet Sauvignon can be relied upon to fully ripen year after year and they can make 100% CS. There is a limited amount of Cabernet Sauvignon planted in the Finger Lakes and Niagara Peninsula of Ontario. It only properly ripens 2-3 times in a decade. But when it does, it is much more like Bordeaux than Napa. Cabernet Franc is a much more reliable crop there.

A quick google search on potassium leves impact on acids in grape yielded this as the first hit
http://www.sasev.org/journal-sajev/sajev-articles/volume-23-2/art5%20effect%20of%20different%20environmental%20factors.pdf
On page 2 nutrient status of soil discusses impacts of nitrogen and potassium.

If, as Howie says, the weather and vineyard practices, such as crop thinning, canopy management, spray programs to control mildews and pests, and drainage issues effect the final flavors in the berries more than the soil content, then how is it that year after year Bordeaux tastes like Bordeaux and Cal cab tastes like Cal cab?... Or are most people going to insist that there is no characteristic Bordeaux taste, and that any such perception is all psychological?

There is no doubt that soil type affects grape quality, but Oliver's question was whether soil chemistry affects grape flavour and that's a different issue (though soil chemistry certainly influences vines via nutrient availability, as Howie alluded to).

It would be extremely difficult to argue that soil chemistry plays a more significant role in influencing grape flavour than do vineyard practises, soil type or climate.

I certainly see a characteristic Bordeaux taste, and it's doubtless because the climate and geology of Bordeaux vineyards is distinct from those of (most of) California. (Soil chemistry doesn't have to even come into it - the differences in climate and geology are probably enough, though on top of that there are many other potential points of difference anyway.) Having said that, there are certainly Bordeaux wines that can be confused in blind tastings with Californian Cabernet by highly experienced tasters (and they tend to be those whose vineyards are managed and wines are made using similar techniques - as a generalisation - to those commonly adopted for Californian Cabernet).

I wonder if there have been any such studies attempting to factor out the variables of vineyard management, vinification process and weather so that it can be determined if any chemicals exist which originate from the soil, and if they can be detected by human sensory and processing apparatus?

I think one of the main problems is that it's so difficult to isolate/separate the variables.

How about if in a laboratory you took five big flower pots and filled each with a different type of typical vineyard soil. Say one with a lot of limestone, another with a lot of iron, clay, etc.; it would be wonderful if you could take samples from actual famous vineyards that everybody knows, such as Lafite, and one from a famous California property. Then you took Cab S. scions from the same vine (if that is the correct terminology) and planted a little grape vine in each pot. Most growing conditions would be nearly identical for all pots in the room. When the grapes ripened, you then extracted juice from each plant and subjected each sample to a gas liquid phase chromatograph. You could also ferment all the little lots and test the juice again after it had alcohol fermented. The different chemical profiles could then be arguably attributed to soil differences. You would have to conduct another experiment to determine if the different chemicals (if there were any differences) could be tasted. You would have to use those identified chemical reagents and put them in liquid, maybe in a glass of simple wine, and taste them against the same liquid without the chemicals.

Covert,

I have wondered for ages why no-one has done the obvious experiment, which would be as you describe; then in pursuing this I did discover that someone in Franconia did it with Muller-Thurgau and Silvaner. Results inconclusive, as I recall.

One of the obvious problems with all of this is that there are so many variables.

It seems to me that growers in Oregon are quite interested in the effects of different soil types on pinot noir flavors in the different ava's there. The "typical" Dundee Hills flavor profile being different from other ava's, based on soil types. Of course this flavor difference may just be my imagination, and not strictly scientific.

as noted, even if there is a noticeable difference between different soil types, it would still be hard to definitively pin to chemistry, as it would also possibly affect drainage, heat retention, etc. That said, for whatever reason I think there are numerous examples where soil types SEEM to impart character to me.

Rightly or wrongly, it's pretty much an article faith in the Loire that soil affects flavor. Films shown at industry exhibits in Sancerre and Pouilly-Fume describe how differences in soil bring about different tastes. One winery in Menetou-Salon brings out a box of different soils and tells you how each of them brings about a different taste. They might be wrong but they believe.

Dan,

I would say that there aren't that many people in the good wine business who don't believe, at some level, and it's been entertaining to discover that the technical view is so restrictive.

Dan,

I would say that there aren't that many people in the good wine business who don't believe, at some level, and it's been entertaining to discover that the technical view is so restrictive.

I'm not privy to the inside scoop, but if the industry is knowingly jerking around visitors who think they are being educated then fie on them.

What?

I would say that there aren't that many people in the good wine business who don't believe, at some level, and it's been entertaining to discover that the technical view is so restrictive.

It's not restrictive, it's open ended: there isn't enough evidence either way.

At the risk of repetition, the soil chemistry issue is different to the soil structure issue. There is support for soil structure affecting wine flavour, but there isn't much data on soil chemistry affecting wine flavor outside of vine nutrient requirements; and there certaintly isn't any evidence AFAIK relating soil chemistry of certain terroirs to wine flavour (in isolation from all the other aspects that influence wine flavour such as vineyard management, climate, harvest date, winemaking, etc).

I'm not privy to the inside scoop, but if the industry is knowingly jerking around visitors who think they are being educated then fie on them.

Dan, I think you read Oliver's comment backwards, he said there are not many people in industry who don't believe it. No jerking (as you say, they may be wrong, but they believe), therefore no fie needed.

I would say that there aren't that many people in the good wine business who don't believe, at some level, and it's been entertaining to discover that the technical view is so restrictive.

It's not restrictive, it's open ended: there isn't enough evidence either way.

At the risk of repetition, the soil chemistry issue is different to the soil structure issue. There is support for soil structure affecting wine flavour, but there isn't much data on soil chemistry affecting wine flavor outside of vine nutrient requirements; and there certaintly isn't any evidence AFAIK relating soil chemistry of certain terroirs to wine flavour (in isolation from all the other aspects that influence wine flavour such as vineyard management, climate, harvest date, winemaking, etc).

At the risk of repetition, it's restrictive, at least mostly so; indeed a number of the papers I've read while researching this are so busy arguing against the 'slate in my wine' idea that they don't really consider the question from the curious, competent winetaster's perspective, which is 'soil chemistry seems to influence wine flavor in certain specific ways, I wonder if there's any way that's possible.' Many of these papers are entirely dismissive of the idea, which is what I meant by 'restrictive.'

It seems to me that science has limitations too, and there are times when some scientists say 'we don't know how this could be true, so it isn't true' rather than 'we don't know enough about this to be sure.' Or as you say, there isn't enough evidence either way.

I'm not talking about soil structure, as you yourself pointed out above.

Hi Oliver,
In itself soil chemistry is a very dynamic feature. There’s decaying material from above the soil working its way down into the soil and “decaying” material from below working its way up into the soil. Then of course there is erosion by both wind and water and the living organism that live in and on the soil that all play a role in “soil chemistry”. I agree with Howie, in the sense that “soil chemistry” (both physical and chemical properties) plays a pivotal role in determining the “health” status of both the vines and grapes they produce. I wouldn’t however compare grape vines to tomato plants. When it comes to tomato plants all you have to concern yourself with is maybe is the first 10 to 15 inches of soil. Grape vines are deep rooting plants and “older” soils with various layers or horizons will be very beneficial to the vines. Each layer or horizon supplies something different to the vines. (Or those soil horizons or layers that are basically useless to the vine the vine’s roots will just pass through it).

Geographer Brian J. Sommers wrote one of the best and easiest reads I read on this subject- “The Geography of Wine”. A notation on the front cover I think says it all- “How Landscape, Cultures, Terrior, and the Weather Make a Good Drop”

Salute

Hi Oliver,
...I wouldn’t however compare grape vines to tomato plants...

I didn't compare grape vines to tomato plants. I compared a pot of sauce to finished wine, both of which have gone through quite a transformation, with lots of process variables.