South Africa Wine Technical Yearbook 2025

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).

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.

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. 

For more information, contact Anton Nel at nelap@cput.ac.za. Reference https://www.wineland.co.za/the-fascinating-world-of-terroir-in-winemaking-part-1/

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TECHNICAL YEARBOOK 2025