The dirt on wine

John Szabo MS reports that the evidence on soil is in, and it’s time to start telling consumers.

Photo by Kyle Ellefson on Unsplash
Photo by Kyle Ellefson on Unsplash

“These days, you can’t say hot, cool, wet or dry vintage any longer. Weather has become totally unpredictable, with extremes even within one growing season,” began Diego Tomasi, director of the Centro di Ricerca per la Viticoltura e Enologia di Conegliano (CRA-VIT) in Italy. To emphasise his point, he projected onto a screen several graphs; one showing the increased variability of harvest dates in Burgundy in the past 15 years compared to the previous two centuries. Another charted the extremes of temperature and precipitation, both highs and lows, experienced in northern Italy in a single year, 2017. “Climate is simply too variable,” he said. “Soils are quickly becoming the most significant factor that defines terroir and wine quality.”

Talking dirty is good business

Tomasi’s presentation was one in a series of technical lectures by researchers in the fields of viticulture and soil management during Enovitis in Campo 2019, the largest viticultural equipment fair in Europe. The 14th edition, held this past June on the top of a vine-clad hill in Montepulciano, Tuscany, was the first to incorporate technical presentations alongside the usual open air exhibitions of the latest in viticultural technology. A wide cross-section of the wine industry, from journalists to scientists, agronomists and winegrowers, gathered to absorb several information-packed hours of talks. They covered specialist topics related to soils and vine growing, from the soil-air interface to advancements in rootstock breeding, soil microbiology and mycorrhizae, and the useful mass of vine roots.

But despite the highly scientific tone, the purpose of the conference was not purely technical. There was a commercial angle, too. “Soils must be better understood if the story of a region is to be properly told, and for the region itself to be valued by consumers,” says Andrea Lonardi, COO of Bertani Domains, whose Trerose estate hosted the conference. Lonardi is proposing an important shift in discourse for wine communicators.

He was in fact the architect of this year’s Enovitis conference, and proposed the topic of soils, an aspect of wine production that he feels is either ignored in wine marketing, misunderstood, or simplified to the point of banality. His goal is to encourage others to reconsider the importance of soils and make them a bigger part of the dialogue: “The characterisation of wine starts in the ground, and the future commercial success of wine depends on this association. Soils need to be part of the discussion.”

Grape varieties, after all, are shared around the globe. Winemaking techniques, too, are universal. Yearly weather is shared by growers, at least at the macro and meso level. So what defines a wine? The answer lies in the dirt. 

Soil chemistry, microbiology, structure, depth and underlying geology are variable, even within relatively small areas. Then factor in the specific subterranean ecosystem created by mycorrhizae, the symbiotic association between soil-bound fungus and the vine’s rhizosphere (root system) that drives nutrient absorption and uptake, and the specificities of place become even more pronounced. Winegrowers can of course modify and amend their soils, but only to a limited degree. They have to work with what they’ve got.

The details of a vineyard’s specific soil characteristics therefore have the potential to make up a wine’s unique selling point. The wine’s DNA, or nature, is further shaped by how it is nurtured, including by choice of grape variety, canopy management and winemaking techniques. Understanding how the complex soil environment shapes the essence of a wine, and then learning how to explain it, should be every winegrower’s goal. 

Dirt in action

The discussion is also applicable on a broader, more general level. Lonardi, for example, has already done considerable research on the influence of soils on the character of Sangiovese grown at Bertani’s three Tuscan estates, Trerose in Montepulciano, San Leonino in Chianti Classico and Val di Suga in Montalcino. And while the research helps him position the company’s wines in relation to those of his neighbours, the information can also be extrapolated to help to define the appellations themselves. 

In a presentation entitled “The Soul of Sangiovese Soils”, Lonardi went into detail on the considerable range of expression of Sangiovese, a variety he considers especially soil sensitive, and which speaks “a common language, though with different accents and expressions”. Importantly, the work goes beyond most of the industry’s current reduction of the soil discussion to simple geology. Lonardi made no claims that Sangiovese tastes like limestone or marl or sandstone, an impossibility in any case. Rather, to frame his results he focused on key soil classification factors such as drainage and water availability, pH, percentage of stones versus sand and clay, available oxygen, levels of calcium carbonate, organic compounds and overall structure. And when it seemed the discussion was heading in too technical a direction to have commercial value, Lonardi tied it back to concrete, digestible wine descriptions.

Through tasting hundreds of samples of pure Sangiovese from multiple sub-parcels, vinified separately and identically over seven vintages (2012-18), he correlated sensory attributes to specific soil types. For example, he described the Sangiovese grown on the alberese (limestone) soils found in parts of Chianti Classico as “more rustic, highly structured, savoury, with meaty, gamy, irony aromas/flavours, blood orange and plum, medium to high tannins, firm and granular, moderate alcohol and high acid”. These he compared to the Sangiovese from pietra forte, a soil derived from sandstone (arenaria) found in parts of Montalcino and Chianti, to which he applies descriptive terms such as “luscious, moderate structure, high volume, highly perfumed, fruity and spicy, orange, candied fruits and Mediterranean herbs, menthol, medium-low, rounded tannins, high alcohol, and medium-low acidity.”

The descriptions are based on specific soil-wine relationships that have been too consistent to ignore. Calcium carbonate content, for example, has a determining influence on Sangiovese. According to Lonardi, soils with high levels of carbonates, such as alberese, produce wines with lower pH and higher acidity, because calcium carbonate reduces the absorption of potassium, an acid buffer. Such observations help to explain in part why the majority of Chianti Classico wines are more acid and angular than, say, Vino Nobile di Montepulciano, which are grown mostly on younger sandy-clay soils devoid of calcium carbonate, and hence are much softer and rounder. 

It’s useful information. Lonardi’s work offers a sensible and useful bridge between science and hedonism, production and sales. It’s a template to follow, one that could be reproduced in any region around the world with aspirations to produce fine wine. Research like this can help clarify and consolidate the messaging of both individual estates and regions and create a cohesive and coherent story that can be shared with both trade and consumers. “Understanding the importance of soil and how it can influence wine quality interests not only the whole production supply chain, but also people who drink it and are called upon to judge it,” said Lonardi, underscoring the utility of this type of work for everyone from grape grower to end consumer. 

The wine trade is certainly eager for such knowledge – a better explanation of causality and more meat to chew. Yet still most winery communications, including technical sheets (which are read almost exclusively by trade) are woefully inadequate for the level of education and understanding of today’s competent wine professionals. More serious information, a story based on something real rather than marketing spin, stands a better chance of raising the interest of buyers, who in turn sell on with more enthusiasm to consumer clients. 

And even consumer interest in soils and their influence on wine shouldn’t be underestimated. Highly engaged drinkers are already aware of a soil-wine connection, so explaining a wine style (house, regional) in terms of soil type, avoiding technical jargon, is not an unreasonable stretch. Soils are potentially the most powerful starting point of differentiation of any wine and should be a more central part of the communication strategy of premium estates. Yet producers, regional associations and PR companies are missing this opportunity to truly highlight the uniqueness of their products. It’s invariably said, but rarely backed by anything concrete. There is still much work to be done, both on the technical and commercial sides, on understanding the impact of soils and how to explain it. 

Diego Tomasi finished his presentation at Enovitis with the bold statement that improving soil-vine root interactions is the only way to progress wine quality. Weather will continue to unfold unpredictably and ever-more unreliably, challenging the very notion of climate. But producers, and communicators, can take refuge in the relative stability of soils, and get to know them better.

Jon Szabo MS

This article first appeared in Issue 5, 2019 of Meininger's Wine Business International magazine, available in print or online by subscription

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