Article: Limestone: Holy grail or charismatic illusion?

This recent article by Alex Maltman on World of Fine Wine really was an eye-opener for me, even if I don’t feel qualified to evaluate the science on the merits (but it seems sound).

Limestone: Holy grail or charismatic illusion?
With so many of the world’s finest wines grown on limestone and its relatives, it’s no wonder that many winemakers see it as the dream soil for viticulture. But is its exalted reputation justified?

Some choice quotes, but do read the whole thing. —> https://worldoffinewine.com/2022/07/28/limestone-fine-wine-soil/

Most rocks and soils are based on silicate minerals, [and] weather down to give somewhat acid soils, with a pH of less than 7, and with similar ranges of water-holding and drainage properties; they all potentially yield the same full range of mineral nutrients for the vine. Just as with, say, volcanic rocks and soils, none has any special ingredient. Neither does limestone, but in its chemical and physical properties, it’s different.

Pure limestone is made of calcium carbonate, based on carbon and oxygen. … they dissolve fairly easily. Also, they weather to give soils that tend to be alkaline—that is, with a pH of 7 or more.
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Two major challenges can face growers working with limestone soils: the possibility of nutrient deficiencies and problems arising from soil pathogens, especially the threat of phylloxera.
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So, is limestone special for wine? Although the rock has never had a monopoly on superlative wines, arguably there was some justification for the claim in pre-phylloxera days when vinifera grew happily in limestone soils on its own roots; there are plenty of modern commentators who believe that those pre-phylloxera vines produced wines unmatched today.
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One apparent attraction of limestone soils is the distinctive quality they’re supposed to give to wine character (seemingly irrespective of the vine rootstock), though there is much inconsistency in the claims. Most commonly, the trait is expressed with words like “liveliness,” “edge,” “nervousness,” and “finesse,” perhaps in line with the notion that the alkaline, high-pH soils of limestone produce low-pH wines.
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[GO READ TO FIND OUT WHY] It would seem, then, that limestone doesn’t confer a special character on wine taste, at least in a consistent way. And as we have seen, for the grower, limestone soils can present challenges.
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Also, paging the resident geologist Ben M a n d l e r.

NOTE: Edited to make the link obvious because people seemed not to actually be reading it.

I think the main benefit is that it means the soils will be free draining and the vines won’t get wet feet. Also Limestone holds water in drier months, meaning there is a supply for the vines.

He answers that one with: “Many of the physical attributes of limestone can be emulated by other kinds of rock. Plenty of soils are free-draining and, usually through clay being present, can offer water storage.”

When did limestone become both free draining and water holding?? That is one neat trick.

I’ve always felt that limestone has its advantages where it rains a lot. Here in California, we need water retention.

Josh Jensen–Mr Limestone-- used to compare his life to that of Manon des Sources. He never found that underground spring though.

Yes, I believe the clay-based Jory soils in the Dundee Hills would qualify for water retention without being too wet and the sedimentary soils in the Willamette valley drain very quickly. We do get quite a bit of rain through fall, winter, and spring.

Calcium is very helpful for skin thickness/toughness in grapes. It’s relatively easy to see how thicker skins could benefit flavor and structure in wines. Thicker skins also help protect against disease pressure on the fruit. Given how many options for improving growing and winemaking are relatively recent developments, it would have been a distinct advantage in the eras where the classic limestone regions developed as highly regarded wine producing areas.

Caves are also common in areas with limestone, and in pre-industrial times would be a huge advantage in wine production. Caves are ideal for many of the needs of producing high quality wines and are probably still somewhat of an advantage even today.

I swear this is all in the article.

At the same time, some limestones contain abundant little gaps between their constituent calcite grains, some enlarged by dissolution, and this allows storage of water. Such a balance between water drainage and storage, particularly well shown by some chalks, is ideal for viticulture. It’s why the chalk strata beneath London and Paris are such important aquifers for those cities.

That calcium-skins link isn’t in the article. Thanks.

Pre-phylloxera, when the vinifera roots could do the acidification trick on the limestone to release iron, that skin thickness benefit sounds like an advantage. But now that they have to use grafted roots that don’t have that trick, is it really that desirable? (Also, still not sure how Montalcino growers deal with the whole boron and zinc problem though.)

Maybe it is, but I got half way through and I couldn’t figure out if the article even had a point, much less what that point might be. Maybe it’s just that I’ve had a long day in the code mines – but he doesn’t write well enough to put up with that.

Oregon soils are Boron deficient. You manage it by adding boron to the soil or spray program. People also lime vineyards when they are being prepped for planting to shift soil pH, and also add calcium to the soil or in a foliar spray. I haven’t seen the grafted plants having issues with assimilating it.

Interesting.

The grafted roots wouldn’t have issues with that unless you overlime too much. What they can’t do is the whole acidifying limestone soils to release the little iron they have.

So let me get this straight: limestone allows for drainage …but into these little aquifers…is that right??
And sometimes the roots can access this water and other times they can’t??

Not quite that, but yes. I won’t speak to limestone, but some clay soils can do basically what you’re post states.

They drain well enough, but are tight enough that they hold a good supply moisture in the soil. Some of that moisture is readily available to the vines, but because of ionic charges, and particle size is so small, some water molecules are held in the soils that grape vines are unable to access.

In Burgundy a lot of the soil is argilo-calcaire…clay+limestone…I am not sure if this is the best of two worlds or the worse.

One thing Josh Jensen pointed out to me, among many, was that there are many kinds of limestone soil. His was a bit different from that in Burgundy…didn’t have any hidden aquifers

Josh’s point is salient both in this thread and a few others on the board lately.

There are a myriad of variations in every aspect of growing and production, from soils to tannins. It’s almost impossible to make wide ranging statements about any aspect of the process of producing a bottle of wine.

I see your difficulty.

You’re applying logic to wine issues.

You know better than that.

Hmmm… not quite. The relative water holding capacity of various soils, and their ability to drain, are two of the most important aspects of any type of soil for most all of agriculture, and the natural system as well. The ability to drain otherwise standing water(ie. not to be a marsh/wetland/bog), is not the same thing at all as the amount of water that a soil can hold. (Which Marcus touched on, and may also be in more detail in the subject article… or you can just google “water holding capacity” for a slew of academic and non-wine connected literature.) Briefly though: the limestone doesn’t drain into “little aquifers”, but there are microscopic holes and pores in the soil grains (soil structure) that catch some of the water as it is draining down to the the water table. Some soils are much better at this than others, thus the vine will have more available moisture longer into the growing season, even without irrigation or mid-season rainfall.

To clarify, clay refers to the size of soil particle, and limestone refers to the soil parent material. Since clay is “simply” soil parent material that has been broken down into particles that are .002mm or smaller, it is not really clay plus limestone, but rather “argilo” is defining the size of the limestone parent material as being broken down into clay(as well as defining a bit more the type of clay.) Although “aquifer” is a bit of a misleading term, the water holding capacity of clay is one of its basic properties**, and so if you had limestone soils without much or any clay, you are correct, there would be no hidden “aquifers.”

(**There are a myriad of types of clay, and the parent material, size of particle, age, ionic charge, etc etc etc will have a massive effect on how the clay behaves, so saying “clay is good” or “clay is bad” will get you into even more trouble than saying “limestone is good/bad”… but since clay particles are so small, they do have an exponential amount of surface area for water to stick to or be held by, regardless of how it behaves after that.)

Very interesting.

I have always felt matching the soil and the climate was key…good drainage where it rains little…difficult w/o irrigation.

Good drainage in France…usually important.
In Napa? Not so much. As a matter of fact here we could use some kind of underground river from Kentucky.

Thanks to Megan and Marcus for their excellent contributions.

Technically this is large and complex question. There are many many geologists whose entire career is within one area of carbonate geology. The following is a hugely simplifed overview.

Limestones and other carbonates are among the most complex rocks systems. Limestones are made from the remains of living organisms. Over geologic time the organisms that contributed to carbonate rocks systems have evolved and changed. This affects the resultant rock fabric. All carbonate rocks start off chemically as Aragonite/Calcite systems. These minerals are metastable which means they can be changed and modified relatively easily. Most carbonate rocks undergo diagenesis very early on in their geologic history. This means they lithify (become rock and not merely sediment) quickly. The rocks are often brittle and typically prone to fracturing.

Depending on their geologic age, the limestones get experience a burial history that tends to get more complex the older the they are. This results in more diagensis and more alteration. This also changes the rock fabric and also leads to multiple eposides of deformation and the associated faulting and fracturing.

The process of karstification (making large voids in the rocks we know as caves and caverns) happens when the rocks get uplifted to above the regional water table. The water flows thru the fault and fracture systems and finds zones of weakness which leads to enlargement and ultimately caves and caverns. Because the karstification process involves water flow over long periods of time these karst system usually have water in them during heavy water flow periods but usually drain out when there is less water flow. Thus means they typically do not act as underground water tanks.

When the carbonate rocks are upifted above the water table, they can form very effective aquifers due to the fracture nextwork. The key is fracture density and fracture aperture. There is a power law relationship between fracture aperture and fracture density (very few large wide fractures and lots and lots of tiny fractures). This is what creates the highly effective flow paths within many carbonate rocks. The fractures connect up the porosity (storage) within the rocks and provide the flow capability (permeability). Lots of small fractures enable the system to hold water

The process of soil creation is called pedogenesis. Pedogenesis is affected by the parent rock materials, biologic activity, climate, time and topography. For soils derived from carbonate rocks, most of the time the pedogenesis happens in situ (in place). Thus over geologic time the rock decomposes, is mechanically broken down and subject to biological activity. The formation of clays is one of the outcomes of these processes. If the parent carbonate rocks are old, then the process of in situ pedogenesis has gone on for a really long time For example in Burgundy they are Jurassic in age which is 200 to 145 million years BP and they have been exposed at the surface for maybe 20 to 40 millions years.

Because most carbonate soils are created in situ, you will pass from top soil, to sub soil to decomposed rock to parent rock. If there is an aquifer system present in the underlying parent rock, it may provide a water souce into the subsoil thru the process of capillarity via the fracture network.

The combination of in situ pedogenesis and connection to the underlying parent rocks and the unusual nature of carbnate derived soils makes them very interesting and complex systems.

To me it is not all surprising that great wines are made from these soils. As a geologist I would say definitely not a charismatic illusion.

Cheers Brodie

Boom! I love Berserkers.

Thanks for the ultra-educational post Brodie.