South Africa Wine Technical Yearbook 2025

biodiversity, increases erosion risk, and can reduce drought resilience by disturbing soil microbial communities and depleting organic matter. This tug-of-war has opened the door for innovative approaches. One such method gaining interest is the use of electric weeders – non-chemical, non-invasive tools that zap weeds at the root. While still in early stages, such technologies reflect the RV spirit of marrying ecological health with practical farming outcomes. The power of mulch and living barriers A promising solution lies in mulching, which involves spreading organic (like straw, wood chips, or vine prunings) or inorganic (such as geotextiles) materials under the vines. These mulches create a barrier that blocks light from reaching weed seeds, suppressing their growth while delivering other key benefits: cooler soil temperatures, improved moisture retention and reduced evaporation. Studies in Spain and California have demonstrated that mulched vineyards maintain higher soil water content and better vine hydration than those relying solely on herbicides or tillage. However, it’s not all upside. In some cases, heavy mulching – especially when combined with no-tillage – can reduce water infiltration by compacting the soil. As with all RV strategies, integrating mulching successfully requires a site-specific approach and ongoing monitoring. Impacts on vine performance and wine quality The effectiveness of weed control measures directly influences vine health and grape quality. A vineyard study in Catalonia showed that spontaneous vegetation left to grow under vines could reduce vine nutrient uptake, likely due to competition. Meanwhile, where herbicide-treated weeds were effectively killed, plots showed higher yields and better vine vigour, although they come with trade-offs in terms of soil health. Mulching, on the other hand, seems to strike a favourable balance. It improves vine water status, suppresses weeds and supports stronger shoot growth, increased canopy area, and even higher grape yields. However, excessive vegetative growth can heighten disease risk and dilute grape concentration, so canopy management remains essential to mitigate these potentially negative effects. Interestingly, different mulching materials can affect grape composition. For example, black geotextile mulch has been linked to changes in berry acidity and lower anthocyanin levels, as well as musts with lower phenolic content and antioxidant activity – reminding growers that even eco friendlier practices can subtly influence wine characteristics. Weed control and vineyard biodiversity How weeds are managed also shapes vineyard biodiversity. Aggressive tilling may initially boost plant diversity, but typically favours short-lived, fast-growing weeds that thrive in disturbed soils. Conversely, less intensive approaches

leafhopper and thrip populations in Californian vineyards. Similarly, faba bean and vetch mixes in Italian vineyards attracted ground beetles and rove beetles, essential predators of pest insects. Cover crops may even help fight fungal diseases like B. cinerea by improving airflow and reducing canopy density. Moreover, their presence supports soil fungi like arbuscular mycorrhizal fungi (AMF), which enhance nutrient uptake by vines and contribute to overall soil health. Greenhouse gas emissions – cover crops in the carbon equation From a climate perspective, cover crops are both an opportunity and a challenge. On the plus side, they sequester carbon in roots and biomass, contributing to lower net greenhouse gas (GHG) emissions. A seven-year study found that a vineyard using barley cover crops with minimal tillage actually had a negative global warming potential – meaning it stored more carbon than it emitted. That said, cover crops can also increase emissions of nitrous oxide (N ₂ O), especially in wet conditions or when legumes are used and fertiliser levels aren’t adjusted. Still, these emissions are tiny compared to the massive GHG footprint of synthetic nitrogen fertiliser production and use. And in the case of legumes, the nitrogen released upon decomposition comes from atmospheric N, not synthetic inputs. Ultimately, cover crops offer a meaningful way for vineyards to lower their environmental impact – especially when paired with thoughtful management practices that minimise disturbance and balance water and nutrient needs. Practice: Smarter weed management Weeds might seem like a minor inconvenience in a vineyard, but left unchecked, they can be serious competitors – vying with grapevines for vital water and nutrients, ultimately cutting into yields and fruit quality. Traditional weed control has relied heavily on herbicides, especially glyphosate, or mechanical cultivation. However, as RV gains traction, these conventional methods are being reconsidered due to their environmental drawbacks. RV principles encourage reducing chemical inputs and minimising soil disturbance, posing a challenge when it comes to managing weeds sustainably. Rethinking herbicides and cultivation The overuse of herbicides is increasingly under fire, both for environmental reasons and due to mounting herbicide resistance among weed species. Concerns over groundwater contamination, impacts on soil microbes, and the carbon footprint of herbicide production are fuelling a broader shift away from chemical control. Simultaneously, mechanical cultivation – though chemical-free – is no silver bullet. Regular tilling disrupts soil structure, diminishes

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TECHNICAL YEARBOOK 2025