Category: SUSTAINABILITY

The Science Behind the Study

What the Results Show

The trial runs until 2027, and we are deliberately cautious about drawing conclusions before final results. That said, the interim report from January 2026, produced by the University of Aveiro, contains findings we believe are worth sharing.

Across all fertilised plots, organic treatments — including insect frass — stimulated measurable enzymatic activity in the soil. Enzymes are the engine of soil biology: they break down organic matter, release nutrients, and sustain the microbial communities that underpin vine health. Seeing this activity increase is a meaningful signal.

Perhaps even more relevant for the long-term health of these vineyards: soil water retention capacity increased substantially compared to the baseline measurement taken in January 2024, when compared to data recorded in July 2025. In a semi-arid region where summer droughts are becoming more frequent and severe, the soil’s ability to retain moisture is not a minor detail — it is a question of resilience. The increase in organic matter, confirmed through loss-on-ignition data, shows that the soil is actively changing.

As for the vines: physiological measurements indicate healthy levels of chlorophyll and carotenoids across all plots, consistent with well-nourished plants. No negative impact on vine health has been identified. So far, the biological indicators are positive.

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Why Old Vines, and Why Now
There is a reason this study begins with old vines rather than young ones. The 40- year-old parcel in Valença do Douro is not ancient — but it represents what the Douro achieves when a vineyard is allowed to mature: deep root systems exploring schist soils, natural resilience to drought, and a relationship with the soil built over decades, not seasons. These are the qualities we aim to understand, protect, and reinforce.

Our ultimate concern, however, lies with truly old vineyards — the centenarian vines of Vinha das Silvas, above the Rio Torto, planted over a century ago and carrying genetic heritage that modern viticulture has largely lost. As members of The Old Vine Conference, a global non-profit organisation dedicated to the recognition and protection of historic vineyards, we believe that caring for old vines is a form of agricultural conservation.

The frass study is the science behind that conviction: a rigorous attempt to understand what these vines require from their soil and how we can provide it without resorting to synthetic solutions. We begin in Valença do Douro because conditions allow us to do the science properly. What we learn there, we intend to bring to the Silvas.

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The University of Aveiro field trial — “Assessment of the impact of frass on plant and soil health and productivity in Douro vineyards” — runs from February 2024 to 2027. It is conducted in partnership with the University of Aveiro’s Department of Biology, CESAM, and EntoGreen, within the framework of the EU-funded InsectERA Agenda Mobilizadora.

New Arrivals: More Hooves on the Ground!

Just when we thought our little sheep family was complete, we welcomed new residents on February 25th—two adult sheep and two small ones!
Our little ecosystem is growing, and with more mouths to graze, the vineyard and olive groves are getting even more love. Watching these animals become part of our landscape has been an incredibly rewarding experience. It’s not just about their practical benefits—it’s about embracing nature’s rhythms and creating a healthy, balanced vineyard where biodiversity thrives.

The Future: More Sheep, More Growth?
With our latest arrivals settling in, we’re already dreaming of expanding the flock. Perhaps more little lambs will be born in the vineyard, strengthening our connection to this natural approach. One thing is certain—the sheep aren’t just visitors; they’re part of the Van Zellers & Co family now.
So, next time you open a bottle of CV Curriculum Vitae, know that it comes from a vineyard where nature leads the way—where woolly workers, ancient vines, and regenerative practices come together to create wines full of life and soul.
Want to meet our sheep? Stay tuned—we might just have some vineyard visits planned where you can say hello to these adorable vineyard keepers in person!


Cheers to nature, to great wine, and to our ever-growing flock!

Francisca Van Zeller

What is Regenerative Viticulture?

Regenerative viticulture is a sustainable agricultural approach that focuses on continuously improving the soil and promoting biodiversity to create high-quality wines while protecting the environment. Historically, wine farming has been associated with intensive practices that can deplete the soil and harm local ecosystems. Regenerative viticulture seeks to reverse this impact by adopting methods that promote biological diversity and a healthy soil.

Improving the Soil in the Vineyard and the Environment

The classic example is in Bordeaux where the two magnificent Rothschild properties, Chateau Lafite and Chateau MoutonRothschild, although sometimes only a few yards apart, have two entirely different styles. The former has perfect poise or balance, and extreme elegance and may be considered the benchmark of the finest claret. Perfect poise and extreme elegance could well describe Baron Eric de Rothschild, who was the family member responsible for this chateau for forty years. Eric absolutely personifies Lafite, as I am sure that his charming daughter, Saskia will future years.

Good Practices from Van Zellers & Co.

At Van Zellers & Co. we have adopted various regenerative viticulture practices to promote sustainability in our old vineyards.

We use a rotation system of different kinds of legume and brassicas  that improves soil fertility and reduces dependence on chemical fertilisers. These cover crops are sown at specific times in the growing cycle to maximise the benefits for the soil. These plants fulfil specific functions, from fixing atmospheric nitrogen to decompressing the soil and protecting it from pests and diseases. Legumes and brassicas are left in the soil after mowing, providing organic matter and protecting it from erosion and nutrient loss.

Another important practice is the use of nitrogen-fixing bacteria, which are sprayed on the plants to promote soil health and reduce the need for nitrogen fertilisers. In addition, a horse will do the ploughing of the soil in the middle of the vineyards to bury organic matter and control weeds, thus minimising the use of herbicides.

Benefits for the environment

By adopting these practices, we increase the biodiversity of our vineyards, allowing the soil to fulfil its cycle and regenerate naturally. At the same time, we contribute to carbon retention and oxygen production, while increasing water retention in the soil. We also foster the microbiological life of the soil, creating and protecting insects, birds, and mammals, which are essential for ecological balance.

In short, at Van Zellers & Co. we produce high-quality wines and contribute to the creation and protection of life in our vineyards, thus promoting a healthier and more sustainable environment.

So, what is it with Old Vines?

As The Old Vine Conference puts it, “old vines are a beacon for talent, innovation, and connection. The best
old vines yield uniquely transcendent wines, incomparably rich in savour, symbolism, and heritage.
The genetic material of ancient varieties, often retrieved from forgotten old vineyards, is proving vital in
adapting to climate change.” My father and I tend to agree, so I decided to record a conversation with him.

CRISTIANO AND FRANCISCA VAN ZELLER HAVE
A FATHER AND DAUGHTER CONVERSATION

[Francisca] Dad, when was it that you understood that old vines
made a difference in the quality of wines?

[Cristiano] As soon as I started making wines in the 80’s, I experienced what types of Port wines would be
produced from younger and older vines. I also began experimenting with DOC Douro wines between 1985
and the early 1990’s at Quinta do Noval, and from 1994 onwards produced wines at Quinta do Crasto,
Quinta do Vallado and Quinta Vale D. Maria from old vineyards.
At Quinta do Noval, we only had old vineyards and the grapes we bought came from younger vineyards.
There was a clear difference in quality, and the wines varied in terms of complexity and variety. The first
vineyards in the modern “patamares” at Quinta do Noval were planted in the 70’s and 80’s.
In the region, vineyards started to be planted by grape variety in the 80’s and it was believed that this was
the best way forward for the region. However, the crucial point of the Douro is the mixture of grape
varieties in a field blend. Today, we plant in a more controlled way, less random than what used to be the
plantings in the early 20th Century. We now decide the varieties that will be planted on certain slopes and
what percentage of each variety will be planted, but we preserve the mixture and high density of the old
way of planting.

[Francisca] What do you think is so important about old vines?

[Cristiano] Old vines have a magnificent capacity to resist to climate changes and fluctuations, which has
been proven throughout time. I am referring to vineyards planted before 1975, where the mixture of
different grape varieties was one of the fundamental characteristics. This blend of different varieties is
what gives wines an amazing complexity. There is a more homogenous maturation of the grapes when they
are mixed in the vineyard. Therefore, we can pick all varieties together. This allows wines to have added
layers and aromas, which would not be possible if we blended the same amount of varieties after
fermentation. Old vineyards in the Douro are then characterized by this diversity and mix of varieties, by
the low productivity of each vine due to their age, and therefore the added concentration that directly
influence, positively, the quality of the wine throughout the different stages of production and ageing.

[Francisca] What has been your greatest challenge in working with old vines?

[Cristiano] Keeping them alive and keeping the diversity; Making sure that when we replant, we maintain the
diversity that originally existed in the vineyard; Guaranteeing that they have a long and healthy life;
The manual labour that goes into their preservation. The old vines are found in high density plantings,
therefore, to work through the vineyard is a challenge and can only be done by foot.

[Francisca] You’ve said that some of the greatest vintages of the 20th Century
were produced with young vines, and not vines over 40 years of age.
The vineyard you planted in 2004 also started producing one of
the Douro’s most acclaimed wines in 2016.
So, is age the main factor in quality?

[Cristiano] Age is one of the factors, not the main factor. When the vineyard is very good at its base, and this means, in the soil it is planted, the density of planting, the care that has been given to the plants,
the varieties that are found in that parcel, age enhances the quality.

[Francisca] When you decide to preserve old vines, does sustainability factor into the decision, or is it an economic and quality concern?

[Cristiano] I would say the answer is both. The Old vineyards in the Douro have an immense biodiversity. If we maintain them, we are preserving biodiversity. The regeneration of the soil where vines are planted is fundamental to be able to preserve the vines and the ecosystem around them. In this way, we can preserve the old vines, therefore the maintainance of these vines, that guarantee the high quality of our wines, calls for sustainability, or, in other words, practices that can sustain nature, the natural environment and the ecosystem where these vines survive. One does not exist without the other: Sustainability guarantees the existence of old vines and old vines are the proof that sustainability exists.

[Francisca] Let’s reset everything. You are starting a new project.
You find a 100 year old vineyard called Silvas, that we know that today produces CV, but didn’t produce any wine yet.
You can only make one wine from it.
Would you make a red Douro DOC or Vintage Port? And why?

[Cristiano] That’s a good question, but I would have to say both. I would use half the grapes that the
vineyard produces to create a Douro DOC red and half to produce a Port wine and try to make Vintage
Port. In fact, that is what I have always done in the projects that I started in the Douro region. I still believe
that the magnificence and beauty of Douro Old vines, is their capacity to produce both great red wines and extremely well ageing Ports.