Why is Limestone Soil Good for Wine?
Many notable wine locations, like Champagne, Burgundy, Chablis, the Loire, and southern Rhône valleys, and Saint-Emilion in Bordeaux, have long been known as being rich in limestone.
Or, to put it another way, these soils are abundant in plant-accessible calcium carbonate, the major chemical component of limestone, which is often derived from degraded limestone outcroppings. (Limestone is too hard for plant roots to penetrate because of its composition.)
Exceptionally, limestone can only be found in a crescent of land on California’s Central Coast between the Santa Cruz Mountains, to the north, and the Lompoc River, to the south.
The presence of calcium-rich soil, comparable to that found at Château de Beaucastel, was a significant consideration in our quest for a location on which to establish our vineyard. The fact that calcium-rich soils were only discovered on the Central Coast narrowed the scope of our investigation to this location.
The west side of Paso Robles and Templeton is home to the state’s biggest exposed limestone layer, and it was here that we purchased our property back in 1989.
In spite of abundant anecdotal evidence of the higher attributes of calcium-rich soils, the science underlying how calcareous soil affects grapevine health and the wines produced by these soils is still being investigated.
It has been discovered that there are four primary reasons why certain soils increase the quality of the wine.
Lumpy chalk walls of caverns in Champagne, France are examples of limestone, which is an umbrella word for many different forms of sedimentary rock.
Limestone includes anything including travertine marble to coral reefs to soft chalk walls of caves in Champagne, France. Limestone soils produce some of the world’s most sought-after wines, which are created from grapes cultivated on such soils.
What is Limestone Soil, and why is it important?
Limestone soils are inherently alkaline, having pH readings in the high range. These soils tend to be in neutral tones of white, gray, or beige, and they have ancient beginnings, as seen by their neutral colors.
Following the receding of water from now-dry seabeds, an assortment of shells, coral, and other detritus gathered, resulting in the formation of calcified deposits. Calcium carbonate is the chemical composition of limestone that distinguishes it from other types of rock.
Agronomic manager at Castello del Terriccio, in Tuscany, Emanuele Vergari, explains that many species do, in fact, have calcareous shells or skeletons that protect them from the elements.
“After the death of these species and years of decomposition on the bottom, the remnants and mineralized components of the organisms combine to form sediments that blanket vast regions of the seabed.
These places have come to the surface due to geological changes that have occurred throughout the years.
Though they are not restricted to a specific geographic region, limestone soils can be found “most commonly in shallow, sunlit ocean waters, where they are formed by the accumulation on the seafloor of calcium carbonate precipitates, as well as the remains of seashells [and] coral debris,” according to Alex Maltman, geologist and author of Vineyards, Rocks, and Soils: The Wine Lover’s Guide to Geology.
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Is Limestone Soil a Good Soil for Growing Grapes?
Growing wine grapes on limestone have its advantages and disadvantages. One of the advantages of this material is its capacity to function like a sponge, soaking up any and all water that comes it’s the way.
According to César Saldaa, president of the Regulatory Council for the Designations of Origin “Jerez-Xérès-Sherry,” “Manzanilla-Sanlcar” and “Vinagre de Jerez,” “Limestone soil, thanks to its incredible water-retention capacity, provides a perfect dosage of water to the roots of the plant, facilitating the absorption of the minerals… needed to produce healthy grapes,”
Some winemakers also commend limestone’s capacity to lower the danger of disease in viticultural areas, which they believe is particularly important.
Daniel de Wet, the proprietor of De Wetshof Estate in South Africa’s Robertson Wine Valley, believes that the mineral content of limestone aids in the formation of disease-resistant fruits and vegetables such as grapes.
The advantages don’t stop there, though. Dr. Laura Catena, founder of Bodega Catena Zapata, and Alejandro Vigil, director of winegrowing at Bodega Catena Zapata, both believe that the mineral richness of the soil relieves stress on the plant since limestone is deficient in other minerals that stimulate plant development.
In addition, there are certain disadvantages.
One of them is that the dirt prevents nutrients from being accessible.
In Paso Robles, California, Matt Trevisan, founder, and winemaker of Linne Calodo notes that because of the high pH of the soil, accessible nutrients take longer to find their way to the plant. “The available nutrients may also be trapped in the soil,” he adds.
In the opinion of Richard Boer, vineyard director of Chalone Vineyard on Monterey, California, “growing grapes in limestone is challenging.” It is difficult to obtain micronutrients like iron, manganese, copper, and zinc into plants because of the high pH, according to him, because of the decreased availability of nitrogen and phosphate.
Possibilities for retaining water
Calcium-based soils offer excellent water-holding capabilities, making them suitable for producing grapevines. A certain amount of water is required for cation exchange, which is the mechanism by which plants absorb nutrients via their roots.
In contrast, damp soils are detrimental to grapevine growth because they increase the chance of root disease.
Soils with high levels of calcium are distinguished by their chemical structure, which consists mostly of sheets of molecules bound together in layers by ionic interactions.
This construction helps the soil retain moisture during times of dry weather while also allowing for efficient drainage during periods of heavy rainfall.
Irrigation is required for soils that are less capable of retaining moisture. A funnel-shaped moist patch in the topsoil is created by drip irrigation, which is directly underneath the dripper.
Because cation exchange cannot take place in the absence of moisture, the only roots that are able to absorb nutrients are those that are located inside the dripper zones of the plant.
As a result, since such zones are in topsoil rather than deeper soils, it is evident why French rules ban the use of irrigation in the best terroirs in France: the wines produced by those vines would be unable to convey the terroir of their origin.
At Tablas Creek, we have become more persuaded that dry farming is, if not the most significant part of making wines of place, then certainly one of the most important. In addition, because of our calcium-rich soils, we are able to dry farm between the months of April to November, when it practically never rains.
Cation exchange and the pH of the berry
It is generally accepted that soils formed from calcium are more basic than soils obtained from other nutrients. The soil pH of the calcareous layers at Tablas Creek is often about 8, which is much higher than the average topsoil pH of between 5.5 and 6.0 seen in the surrounding area.
According to research, cation exchange is larger at higher levels of base saturation, perhaps because the majority of the minerals required by grapevines are more readily available when soils are more basic.
Increased calcium content in soils is also associated with greater ease of nutrient absorption. By using a mechanism called cation exchange, the nutrients that a grapevine needs to survive (magnesium, potassium, calcium, and sodium) are taken up by the plant at precise places on the root hairs and stored there.
Plant roots contain chemicals that are negatively charged, which attract positively charged cations. Calcium aids in the aggregation of soil particles via a process known as flocculation, which in turn aids in the availability of additional cation exchange sites to a plant’s roots.
As the pH of the soil falls below 7.0, hydrogen ions begin to displace the ions of the four major nutrients.
All four nutrients are easily accessible only when the pH is greater than 6.0. Consequently, calcium carbonate works as a buffer (it has been used as an antacid for ages) and neutralizes the acid produced by the decomposition of organic materials in soils. Ultimately, this results in a pH level where nutrient availability is at its peak.
Finally, there is emerging evidence that soils high in calcium may aid in the preservation of acidity in grapes throughout the late stages of the growing season. Increased grape acidity and lower wine pH, according to studies conducted at the University of Bordeaux, may be attributed to healthy cation-exchange mechanisms in soils rich in calcium — and with sufficient water — And we have plenty of anecdotal evidence to support this claim.
Two summers ago, at a Roussanne symposium held in Paso Robles, producers from the eastern part of the county, where calcium-rich soils are rare and rainfall is consistently lower, consistently reported harvesting Roussanne with a pH half a point higher than those of us on the calcareous (and wetter) west side.
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The growth of the root system and the vine
Grapevines, in contrast to grains and other annual crops, which have shallow root systems, have deeply rooted structures.
For vine health and wine character, this indicates that the deeper soil layers have a greater influence on their respective compositions than does the topsoil layer.
It also implies that modifying the soil (for example, by liming to add calcium) is less successful than the natural replenishment of important minerals from deeper levels of the soil structure.
The roots of the grapevine are extraordinary. Their ability to penetrate hundreds of feet into the soil in quest of water and nutrients is unmatched, and they continue to grow for the duration of the vines’ existence.
In this case, the physical characteristics of the soil are critical: a hardpan layer through which roots are unable to penetrate may have a significant negative influence on the yield of a vine.
The propensity of calcium to cause flocculation (aggregation of soil particles) results in the formation of gaps into which roots may penetrate and in which water can be stored.
This characteristic is especially essential when dealing with clay because clays rich in calcium tend to have better soil structure and less mechanical resistance to roots than clays low in calcium.
Long periods of dry weather also cause clays to dry up and fracture, enabling roots to penetrate deeper into the soil where more residual moisture may be discovered, helping the plant to flourish.
Even in our vineyard, which is still in its infancy in terms of vineyard age, we’ve discovered roots 10 feet deep or deeper in experimental digs.
Aside from that, soils with low calcium content — such as those with limited water availability — have a tendency to exhibit excessive exploratory root development and may have massive, inefficient root systems that support just a modest amount of rather poor aboveground growth.
And this makes sense: vines have a limited amount of energy to allocate between root development, canopy expansion, and fruit ripening. This allows them to maximize their yields. If they are compelled to use more energy in their hunt for calcium, they will have less energy available for other activities.
Disease resistance is a term used to describe the ability to withstand disease.
At long last, there is evidence to suggest that calcium is required for the development of disease-resistant berries. Calcium is present in high concentrations in the skins of berries, and it is necessary for the formation of robust cell walls as well as the maintenance of skin cohesion and elasticity.
When calcium is limited, plants favor intracellular calcium over berry skin, which is why berries have thin skin. Calcium and berries are both more sensitive to enzyme attack and fungal illness than other foods and beverages.
We’ve believed from the outset that limestone was essential to the production of excellent wines. It’s fascinating to learn about the scientific evidence that supports our beliefs.
In Wine Regions, Limestone Soils are Found
According to Sebastian Nasello, winemaker and CEO of Podere Le Ripi in Montalcino, Tuscany, “Limestone soils are quite scarce around the globe.” It is estimated that just 7% of the rocks are sedimentary, with the majority of them being limestone-based.
Burgundy, Champagne, Jura, and the Loire and Rhône Valleys in France; Jerez in Spain; Tuscany, Sardinia, Veneto, and other minor pockets in Italy; Mendoza in Argentina; the Robertson Valley in South Africa; and Paso Robles, California. Limestone soils are found across Europe and the world. Because of their geological histories and ages, different locations have diverse kinds of limestone soils.
Because the continental block on which modern-day France sits was “blanketed with carbonate deposits as Europe drifted away from North America through the Tethys Ocean,” says David Howell, a retired geologist and founder of Wine and Geology Tours in California, the country’s soils are predominantly composed of limestone.
French wine regions are all “underlain by varying age limestone,” according to the author, who goes on to describe how the country’s numerous wine regions are formed. Derived from the Triassic era around 200 million years ago, Alsace is the oldest of France’s regions, while the right bank of Bordeaux is its youngest, having been developed during the Tertiary period approximately 60 million years ago.
Excitement Regarding the Grapes
However, the judgment is still out on whether or not soil influences the flavor of finished wines. It’s a contentious topic in the wine business, with those who think it does and others who feel it is a fairy tale on opposite ends of the spectrum.
Geologists and other professionals with scientific backgrounds are more likely to fall into the latter group than the former one.
There is no genuine proof that soils have an impact on the taste of wine, despite common belief, according to Maltman.
Winemakers, on the other hand, have a distinct point of view.
The minerality and brilliant natural acidity produced by limestone-grown grapes, according to Trevisan, are particularly notable. Vigil believes that wines produced in limestone have “freshness and longitude” in their character. There is no explanation.”