By Zukhanye Fondile, Tracey-Lee Johannes, Relebohile Mabaleka, Zinhle Msiza, Imi Mxabo, Ziphozinhle Nkosi, Neo Segopolo, Ezile Zitha & Anton Nel
In the first part of the Terroir series, we explain the concept of terroir. Then, we will look at the different elements influencing the terroir concept, starting with soil. We will end with the influence of climate which we will continue in Part 2 of the series.
What is terroir?
In the world of wine, the term “terroir” is both a buzzword and a concept rich in tradition. Terroir refers to the combination of environmental factors and human practices that give the wine its unique character, shaping everything from flavour to quality. The term originated in France during the mid-19th century and has gained global recognition, especially with the rise of international wine markets (Trubek, 2009).
At its core, terroir involves more than just geographical location – it’s about the intricate relationship between land, climate, and the hands that craft the wine (Valgenti, 2022). This holistic perspective has allowed the term to serve as a legal definition in regions like France, where Appellation d’Origine Contrôlées (AOCs) govern product origins (Barham, 2003). However, terroir is as much a cultural and philosophical idea as a practical one, encompassing history, human effort, and the social context of wine production (Charters et al., 2017).
The key elements of terroir
Environmental factors
When wine lovers speak of terroir, they often refer to the specific environmental conditions that influence the grapevine. This includes soil composition, climate, and the way these interact with the type of grape being grown. For instance, the soil’s mineral content, texture and depth play a crucial role in determining the grapevine’s health and, subsequently, the wine’s flavour profile. Likewise, climate factors such as temperature, rainfall and sunlight are essential in shaping the ripening process (Van Leeuwen & Seguin, 2006).
These environmental factors form an “interactive ecosystem”, as Seguin and Van Leeuwen (2006) describe it, where each element works together to create a unique environment for the grapes. This is why two vineyards, even just kilometres apart, can produce wines with noticeably different characteristics.
The role of human practices
While nature plays a significant role, human practices are just as crucial in defining terroir. Historical and cultural contexts shape how vineyards are developed, from selecting grape varieties to the viticultural techniques employed. Over centuries, winegrowers have learned how best to work with their land, perfecting methods that allow them to express the nuances of their terroir (Charters et al., 2017).
The choice of grape varietals is crucial. The most successful vineyards often plant varieties perfectly suited to the local climate, allowing the grapes to ripen fully by the end of the growing season. For red wines, moderate vine vigour is vital, while white wines benefit from a delicate balance of nutrients, particularly nitrogen and water.
Quality and ripeness
At the heart of terroir is the pursuit of quality. Grapevines that are well-matched to their environment are more likely to produce wines of superior quality. Conditions like moderately dry climates and nutrient-rich, well-drained soils are perfect for producing top-tier red wines. White wines are all about the perfect balance of ripeness (Van Leeuwen & Seguin, 2006).
Historical and socioeconomic influence
Finally, we can’t ignore the influence of history and socioeconomics on terroir. Factors like proximity to markets or trade routes have often shaped the development of vineyards. Regions with a long-standing winemaking tradition tend to have a deeper understanding of their terroir, honed over generations of trial and error. These historical practices have often been formalised into laws and regulations that govern everything from planting techniques to harvest times (Charters et al., 2017).
How soil shapes the world of wine – the hidden factor behind terroir
When it comes to wine, we often hear about terroir – the unique combination of climate, geography and human touch that gives the wine its distinctive character. However, soil is one of the most crucial and often overlooked terroir components. Soil is the backbone of the vineyard ecosystem, providing water and nutrients to the vines and playing a significant role in grape quality and vine development.
The role of soil in terroir
Soil impacts vines in various ways, from temperature regulation to water and nutrient availability. The temperature of the soil, for example, can affect the timing of the vine’s life cycle or phenology, influencing everything from bud break to harvest (Mase et al., 2015). It’s not just about where the vineyard is located, but how the soil interacts with the climate and the specific grape variety planted there. This complex relationship between soil and vines is a cornerstone of the concept of terroir, shaping the wine’s taste and quality.
Soil is a critical component of terroir and directly impacts the quality of grapes. Characteristics like soil depth, moisture content and texture play a role in vine growth and grape development. For instance, deeper soils allow vine roots to penetrate further, providing stability and enhancing access to water and nutrients. This, in turn, affects grape quality by influencing vine vigour and berry composition. Reduced water uptake, for example, can lead to smaller berries with more concentrated tannins and anthocyanins, which are crucial for wine colour and structure (Matthews & Anderson, 1988; Van Leeuwen & Seguin, 1994).
Soil texture also plays a key role in water retention and permeability. While great wines are produced in various soils, even those with high pebble content or clay, the soil’s ability to retain moisture without becoming waterlogged is essential for optimal grape quality (Seguin, 1983, 1986).
The impact of soil quality
Soil quality is critical to the health of vineyards, but many regions face challenges like soil erosion, which can seriously impact wine production. Intensive farming practices – like herbicides and heavy machinery – are known to increase erosion rates, depleting soil quality over time (Ji et al., 2002). Vineyards, particularly those in Mediterranean regions like France, Italy and Spain, experience higher soil erosion rates than other types of orchards.
Interestingly, while soil erosion in vineyards is a significant concern in scientific circles, it hasn’t always been treated as an urgent agronomic or environmental issue by farmers. However, recent studies are starting to shift the focus, revealing how important soil is not just for grape growth, but for the long-term sustainability of wine regions.
One fascinating experiment highlights how soil quality directly impacts grape traits. This study tested three distinct soils from different Italian wine regions – Valpolicella, Valdobbiadene and Legnaro – under the same climatic conditions, using the same grape variety (Corvina). The results showed apparent differences in grape development and quality based on soil type, underscoring just how critical the “right” soil is for achieving a balance between grape variety and its production area.
Soil texture – a key player in grape quality
Soil texture – the mixture of sand, silt and clay – also plays a major role in determining the quality of grapes and, consequently, the wine itself. Research conducted in the Niagara Peninsula of Canada explored how soil texture and vine size influenced the characteristics of Chardonnay wine over three vintages. Although no definitive trends emerged across all sites and years, certain vintages showed clear differences in flavour and aroma based on soil texture. For example, in one vintage, wines from clay-rich soils were noted for their citrus, vegetal and earthy qualities, while other vintages had more floral and melon-like aromas. Overall, while soil texture is just one piece of the puzzle, it interacts with other factors like vine size and climate to shape the sensory profile of the wine.
Irrigation and its effects on soil
The availability of water in the soil can greatly impact vine behaviour and berry composition. Water stress can influence the quality of the grapes, particularly the concentration of important compounds like amino acids, which play a key role in fermentation and flavour development. One study looked at how irrigation affected the amino acid composition of Albariño grapes in two different terroirs in Spain (Soufleros et al., 2013). Interestingly, irrigation did not significantly change the total concentration of amino acids, but it did alter the levels of certain amino acids like methionine, which could influence the aromatic profile of the wine (Soufleros et al., 2013).
Albariño, known for its fruity and floral aromas, has become an increasingly popular white grape variety not only in Spain, but also in regions as far as the United States and Australia. This study shows how soil management, through practices like irrigation, can influence not just grape growth, but also the sensory characteristics of the final product (Soufleros et al., 2013).
The bigger picture – soil, climate and terroir
The importance of soil cannot be overstated when it comes to wine, but it’s only one part of the larger terroir puzzle. The climate also plays a significant role. For example, a study on Merlot, Cabernet Franc and Cabernet Sauvignon vines grown in three different soil types revealed that while soil and climate both impact grape quality, soil’s influence is often mediated by how much water the vines can access (Van Leeuwen et al., 2004).
Understanding how soil, climate and grape variety interact can help winemakers adapt to changing conditions, such as those brought on by climate change. As the planet warms, traditional wine-growing regions may need to adjust their practices to maintain the delicate balance of terroir, and soil will be at the heart of these adaptations.
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For more information, contact Anton Nel at nelap@cput.ac.za.
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