Healthy soils under a regenerative approach: Mimi Casteel, Teresa Martinez, Álvaro Martinho and Cristina Calheiro

Healthy soils under a regenerative approach – Climate Talk Highlights

On December 3rd, for our Climate Talk we invited some of our members to explore and debate the importance of how it can represent a solution to tackle the climate emergency in the wine industry.

To host this Climate Talk we invited Cristina Calheiro (Ciimar – Portugal) and counted with Mimi Casteel (Hope Well – USA); Teresa Martinez (Gramona – Spain) and Álvaro Martinho (Real Companhia Velha – Portugal) as guests.

Various solutions and practices were shared. Here are a few of Porto Protocol highlights on our Climate Talk on “Healthy Soils under a Regenerative Approach”, to inspire change. We invite you to read some of the most important messages,  that we resume on the following topics:


Cristina: Today is the 3rd of December, but we are approaching also an important day that is the World Soil Day, celebrating healthy soils for Earth’s food-secure future. This year’s slogan is “Keep soil alive, protect soil biodiversity,” so gives importance also to the workers below ground, from bacteria to fungi and all the earthworms and the other organisms that provide so important ecosystem services, such supporting plants that gives us the oxygen, but also the carbon sequestration. This is really a huge universe, the soil that we only know about 1% of the biodiversity.

When you talk about wine production, we are also talking about what it stands below the vineyards, the soil, and in what they are contact with, that is the climate. We have the climate change, and we have the soil; two factors very important, and they are interconnected.

  • What is the role of soil towards climate change mitigation and adaptation? Why soil is so important?

Mimi Casteel: Soil has the capacity to store up to five times more carbon than the above-ground biomass that we currently see on earth. Five times more than what the plants can store, the soil can store. That’s really mitigated by that transactional layer of soil that our agriculture deals in. That aerobic zone, topsoil is what we call it, it’s the biological component, is where all of that carbon is transacted, and then can be stored in deeper layers of soil.

It is my feeling that we don’t have a much greater hope than our soils to be able to impact climate change. We certainly need to deal with emissions.

If we don’t also deal with the broken sequestration pattern that we have created through agriculture, there’s not a lot we can do to impact the severity of climate change going forward. I think soil is our greatest hope.

Teresa Martinez: Soil for me is the center of agriculture. I understand the soil like an iceberg. When we see an iceberg, we only see a little part. That part for me is the plant, for agriculture. The rest of the iceberg is the soil, all the capacities, characteristics and all the life that is inside. It is important to arrive to the plant and work under it, work this iceberg or this earth.

Álvaro Martinho: Soil is the place where everything begins. Everything we do at Real Companhia Velha, what we did in the last 20 years, is to protect the land. We keep the vegetables cover to protect it. The soil, to us, is the most important factor of differentiation when we talk about quality in terms of the grapes.


Cristina: I think you mentioned something very important. That is, also having consideration, the history of the soil, and the observation of the nature, because sometimes we want to change what is around us, but we have to listen to the nature and also go along with her.

  • What do in your land, in your property, in terms of regenerative practices? What do you apply? What do you do? This is to talk a little bit of you of what you do daily, and how you work with your land?

Teresa: Our soil is a little bit like Douro, we don’t have so much organic matter, content, around 0.5%. My aim is to increase that, I hope, to 2%, but it is really difficult.

  • As a biodynamic producer, we work a lot with the compost to arrive at this percentage.
  • I also leave the pruning stubble.
  • I use two kinds of cover crops. One to protect the soil during the winter, our out-of-tone green plants and have also been working with green manure for three years now.
  • I do minimal plowing. This has two variants: Machines: we have changed the wheels of the tractors to another kind to reduce the compaction. Also, we work with animal tractions since 2017 and all the vineyards that were with this, also we have changed all the machines. We don’t work with tractors. We work with quads to avoid the compaction and let the horses work better.
  • I also like to control the place where my animals are eating because we have a lot of animals. It is very important to change the place because they really can destroy the soil if you don’t control it. For example, I explain Gramona like an organism: we are winegrowers, but we do a lot of things: we have olives, forests, orchards. That is my organism. I try to provide all the things. For example, to the soil, when I organize the forest, I provide pine bark and I put it in the new vineyards to reduce the impact of the heat in the vineyard for the first year, as the summer is really hot here, and the rain is scarce, like 500 liters per year, but all in the winter.

That is the idea of biodynamic principles. I want to close my organism and my aim is to be self-sufficient. I have my cows for my compost, my sheep for the same, for pasteurizing the vineyards, to control the grass in the forest. It is difficult, but with the pass of the years, you can control and arrive to an equilibrium.

Mimi: Our farm used to be a commercial Christmas tree farm, very poor health when we arrived and no measurable organic matter. One of my primary goals is to grow new topsoil, new organic matter.

  • We don’t use any plowing or any cultivation.
  • One of my frameworks for regenerative practices is applying an ecological structure to the farm so, as much as possible, emulating what a fully functioning ecosystem would look like architecturally and facilitating the nutrient cycles that are usually not present on an agricultural piece of ground.
  • Pushing as much diversity into the vineyard as possible, both animals and plants. We’re really trying to incorporate animals into the vineyard system to cycle nutrients faster, and help build out organic matter a little bit quicker.
  • We have a pretty diverse landscape that we’ve been reestablishing. Where there used to be Christmas trees, we have replanted trees that are good for both structure and function within the vineyard itself.
  • We use the animals in the vineyard and then in the forested areas.
  • We also have a large vegetable garden and orchard.

Álvaro: Douro is very complex region and it’s impossible to find one solution for everything. One vineyard is one identity.

  • I think we need to look to the past. For example, the system pruning. In the last 20 years, Douro Valley adapted just one system: the cordon. In the last 20 years, we changed all our system pruning. The vineyards need to produce more, to use more water, will need to use more nutrients. We need to renovate that system pruning and adapt the whole system pruning. Short, lower, and with this system maybe it’s more defensive to the plants.
  • We use cover crops. Regarding vegetation, we have two or three situations. One is the indigenous cover, the plants that exist in there, and it is a good blend of the plants. Those plants need to stop growing before May, so we cut minimum, usually two times per year. That technique is very important because it protects the soil and avoids erosion when the rain comes pouring fast.
  • And we think that vegetation stimulates life inside. To me, this is the best characteristic, but we wait for this technique to stimulate life microorganisms in the soil. No nutrition, the soil never offer nothing if you don’t have microorganisms inside. To us, we think that technique is very important because our percentage of organic matter is very, very low. When we have 1% of the organic matter, to us, we think it’s a rich soil. Usually at 0.5, 0.7, 0.2, so it is our reality. The pH is acid and of course that technique is very important.


Cristina: It is really important to plan; to plan long term, not think short term and immediately production. That’s really a big issue.

  • Have you seen already differences in terms of quantification? You introduced those practices. Have you seen increase of production or any quantification, already some results? how it’s important to do the observation, but someone says metrics are important, too, and the quantifications. I don’t know if you do any practice related to that in terms of management?

Mimi: Though our capacity to measure deep stored carbon on agricultural soils is a little bit behind and kind of prohibited right now, we have been able to measure the increase in organic matter, which is a good proxy for how much soil carbon you’re increasing.

We do a lot of soil counts, basically. We look at our invertebrates, our earthworms, and our beetles and all kinds of things.

We also have a complete inventory of the plant species on the property so that we can measure the increase in biodiversity and the return of native species.

We’re always looking out for the return of certain songbirds that have been largely excluded from the agricultural lands just because of lack of habitat. We’re really looking at indicators of certain species that are affiliated with different plants that we’re reinstalling in the farm to see whether or not that facilitates even more biodiversity as we go.

In the last 12, 13 years, we’ve been able to steadily increase our organic matter to the point now that we’re close to 10% almost everywhere. That went from zero to 10. We do have a much more generous rainfall pattern here. The amount of water that we receive, I think, and the addition of animals really does help to increase that organic matter faster.

Teresa: It’s really important to measure and we measure a lot of things, but we can’t forget observation.

I want to explain about the horse that we talk. I’m doing an essay to measure, mainly, the compaction about penetrometer and also I measure the infiltration. I’d be glad if there are- in this group, if there’s someone who wants to participate because I would like to collaborate with some scientists.

There are some words that a teacher says to me at the university that says; if you don’t measure you can improve, and what doesn’t get better it gets to degradation always. It’s really important to measure. Like Mimi, we measure a lot of things, but it is important to differentiate these two kinds of- not agriculture, of person. We can measure but we don’t have to forget what we are. It’s really necessary, the observation.


Cristina: It’s an actual challenge, for vineyards and food production leaving the use of herbicides.  You also study this situation of using herbicides and the impact that can have.

  • What other solutions there are that people can use, can be an inspiration in that work, because normally people say, “This doesn’t work,” and they give up? 

Mimi: We don’t use any herbicides or systemic chemicals at all. We’re organic certified. My journey really started just around wondering how some of these systemic chemistries behave in the soil environment, and then also in the metabolism of our plants because that is not usually the part that gets spoken about when these chemistries are being marketed to people.

We’ve even stopped the underground, under the vine cultivation. That’s really to keep a stable root system near the vines of other plants interacting with the vines. I do understand the concerns about competition, especially. We have worked very hard to find the right types of plants that have a seasonality that is a little bit different than the grape-growing season, so that they’re basically dormant during the time when our grapes need more water, but that those roots are still actively holding soil in place, and are contributing to the storage of carbon and the translation of other nutrients to the area around our vine roots.

Our vineyards look a particular way. It doesn’t look very tidy, whereas just bare underneath the vine, it’s very fluffy and very diverse. We’ll use the animals to graze some of that down during certain times of the year. We also use a tool that kind of just mows right under the vine. We’re on steep hillsides as well. I don’t think it would work in the Douro Valley, just because of the challenge of having machines there. Where it’s very steep, we use animals for that.

I’ve eliminated the word weed from my vocabulary because I think all plants are contributing in some way and being mindful of what each plant is bringing to the table and just trying to learn from what the ecosystem is telling you. It takes a very long time to rebalance the water, carbon and the nitrogen cycle, and just being patient through that. It is often at odds with an economic standard, especially a capitalistic economic standard.

Álvaro: Regarding herbicides, comparing 2002 and 2019, we used 78% less. We have a lot of the vineyards without herbicides. In a lot of the vineyards, we use just in the line of the vines.

At the moment, sometimes we use it. In the vegetation, it’s a problem to the vines. We need to remove that. We need two seeds with another species. It’s very, very important, like leguminous, like peas, like Lupinus, that species that have very positive actions to them.


Cristina: That is because you told about the animals in the vineyards, the increase of biodiversity, and the speed up to build off the nutrients in the soil.

  • They would like to hear about what types of animals, and how does the rotation work.

Mimi: I have found that, just in studying the ecosystem that we’re in, and most of these ecosystems where vineyards are grown, animals were a critical part of the cycling of nutrients, and especially the growth of more organic matter and topsoil. When it’s possible, using a ruminant, some kind of a ruminant animal, so we use sheep. We also have chickens and ducks and various other things, but sheep are the primary grazers in our system.

We move them very intentionally at different times of the year. They basically have to eat a lot in one little place and then they move very quickly, as if a predator were moving them to mimic the way a ruminant herd would move across the landscape. That really does stimulate a flush of root growth in your ground cover. That can push a lot of sugars and store a lot of water much faster than if you don’t have the capacity to have animals in the system.

But they do have to be managed. We do a lot of moving electrical wire paddocks around the vineyard. We do that pretty much everyday or every other day during the growing season. It really has helped to grow organic matter faster where we’ve been able to use the animals.

Teresa: The animal part is the more difficult to build, to integrate in the organism.

In Gramona we have a lot of animals. We have cows, an autochthone race from Catalonia. We collaborate with these cows to promote these animals. Normally they are in the forest because they clean perfectly, but I have to stop and change.

This is the same with the sheep. I use them in the binders, normally in winter. In spring, I must stop because when the binders have leaves, it’s impossible to control them.

We also have horses who pastorate. We have a farm allocated for them but they also pastorate in the headlands.

We have chickens, geese, ducks, bees. These were the last animals we have incorporated because everybody is really concerned about the water and the food of their water, but I thought that it’s also important to control the air. These are the best animals to control it if your air is clean or not because if not, they all leave.

I also use electric materials to control. I think it’s really interesting to integrate all these animals because you can have a lot of profit from that. Especially for me, the cows are very important because it enables me to do all the biodynamic preparation for me and for all the groups that work together here. It’s not only what they can apport to this soil as organic. it’s the feeling or the connection that you can create between the plants, the animals, and the humans. For me that is agriculture. That is my objective.



  • The equilibrium of the ecosystem. If we have a more resilient and healthier ecosystem, it can also be more prepared for the challenges of climate change and these extreme events, right?

Mimi: Technically, the more stable and more permanent a system becomes, the greater the cooperation as opposed to competition between organisms in that system. We know that in perennial systems plants share a lot of information and nutrients and water. Really getting past those thresholds where you’re working, or just waiting for the equilibrium to come back, it’s a challenge, for sure.

I think that we do need to look at native ecosystems to get a sense of what needs to be restored from a connectivity, so connecting landscapes to one another. So that ecological thresholds for resilience can actually be achieved and that agriculture, whether the agriculture itself is an indigenous crop or is an introduced crop, it needs to be integrated with as many indigenous characters as possible. Not just plants but the animals as well. Because of that flow of species and those communities of species, they co-evolved over millennia in order to achieve the productivity and the stability that they had before we put agriculture there.

So it’s our job now to start putting that back together and pulling the threads back across our fence lines because we’ve really interrupted those cycles in a very macro way. If we want the climate to benefit from our agricultural practices, we need to have in mind that at the farm scale, we will be limited by what we can actually achieve, unless we’re all working together as an agricultural community as a greater landscape to achieve larger goals of resilience and connectivity.

Álvaro: When you talk about climate change, sustainability, ecological, we need to look not just for the soil just because everything is important. What you plant in your soil, what typical grass you have, if you are watering vineyards or not? Herbicide is important or not? Soil ionization is important. The workers that you have. That activity is very global.

That activity requires 20-year planning. We started defining what we wanted in 2002. To us, the important thing is to implement a sustainable viticulture and we need to look at three factors :

  • The economic factor. Douro Valley is a very characteristic region in the world, where 75% of vineyards are in steep conditions. When you walk, drive, work, everything is different if you stay in steep or flat conditions. It is very hard to work.

So the first factor is doing sustainable viticulture economic. How much to pay to get 1 kilo of grapes? In the old, traditional vineyards, we need 500 hours workers per year per hectare. It Is very, very expensive, hard and difficult to introduce any machines in these vineyards.

In terms of economics, in our region, our productions, the average is 4,000 kilos per hectare, sometimes a little bit more. When you talk about old vineyards, sometimes we have 3,000 kilos per hectare. It is a low, low production when we compare other regions.

  • Another very important factor is the social, the people who work with us. It doesn’t make sense to talk about ecological sustainability if we don’t offer good conditions to the people who work with us in the vineyards.

We were the first company to pay the same salaries to men and women. At this moment, I have a group with 45 workers in vineyards. 80% are ladies. It’s not just salary; it’s good conditions, transport and good environment for them.

  • Another factor very important is the equilibrium with the environment. Of course, we need to be careful about everything, the treatments. We started making disruptions against grapes. It is a biologic system to avoid– That method, in 2010, we started, but at this moment, we don’t use any insecticides.


Teresa: The two kinds that I use; one is about the plants that grow there. I use it during the winter to avoid erosion because we have a lot of rain..

I plant under the vines because, if not, after I don’t have time to control it because you need the tractor, five hours per hectare with a VENTRAL machine. It’s five hours per hectare and with the horses, it’s like 12 hours for hectare to do that. I prefer to control it during the winter because if not, when the spring arrives, I can´t manage all my hectares.

The other kind of cover crops that I use are with the objective of fertilizing a bit. All the winter I pass with these plants, but also to fertilize, I select different kinds of plants this year. I could explain. I work with a leguminous, Rye, Oat, Gramineae. Mustard, Cruciferae.

I change the kind of plants depending on the vineyard. Normally, if I don’t have low production but if I want to help a little bit, I put more leguminous. But I have vineyards where the clay, that as you know is very oxidative and it needs to eat a lot and also it’s really difficult to work the soil. I prefer to work more with gramineous because with the roots, it’s like little plots of the soil. Those are my two kinds.

When the spring arrives before the seeds- produce their seeds I cut it, I wait for like two years and after, I incorporate all under the soil. Depending on the condition of the years I let the grass more months or not, because the summer here is really hard. In 2020, I had cover crops all the year because it was terrifying, it was the worst mildew year that we can remember. But 2017, it was impossible because the grass can grow up, the conditions are so extreme that we don’t plant but we don’t have grass.

Álvaro: We keep the vegetables covered; The vegetations, we cut just one or two times a year. This is the only chance that we use to protect our soil, is to keep the vegetations in the ground. We need to be careful because when vegetations are growing after May, it’s a competition of the vineyards. We need to be careful.

Another side, sometimes we need to seed some species like Peas Lupinus, when in fact we need to apport nitrogen in the soil because. This is the most natural way which we input nitrogen into the soil. We have another vineyard. Not too much, but we have in Carvalhas four hectares, and it’s impossible to keep the cover with vegetations. So, we need to spray this area because is too steep. Between 10 weeks a year to remove- to mobilize the soil and sometimes to control the grass. Of course, to complex more this, we have organize our vineyards with the vertical way, with the terraces.


  • Tell us about the use of the indigenous plants and how important are their presence?

Álvaro: I use a lot of hours to observe different varieties and different plants, when I walk in the middle of vineyards but also all around the vines.

In the Douro Valley, we plant 120 different varieties. It’s too much. Mostly our indigenous varieties like Tinta Francisca, Tinto Cão, Tinta Barroca, Touriga Francesa; it’s a lot of varieties. We need to do that interpretation. That species, that Vitis vinifera found a place in Douro Valley, and that place was a great place because those species developed a lot and created 120 different varieties. It’s incredible. That represents that richness, what that valley represents to the plants. Not just all the plants, in the vines also.

We need to use maybe our indigenous varieties. That represents of course low production, but authenticity in terms of the quality.

We don’t talk about just sugar or alcohol, we talk about ingredients, flavors, everything. This is that plants indigenous can survive in that extreme conditions. When we look to old vineyards with the 75-95 years old, of course they could do just 1 kilo or 0.5 kilos. Sometimes, we need three or four plants of the vines to produce one bottle. This is our reality. When we talk about premium wines, we need two plants in the medium to produce one bottle of wine, but you can keep this wine your life.

The soil in this equation is very important because those plants can grow deep- not two meters but sometimes three to seven meters- it is not excellent soil but gives what the plants need, and the indigenous plant needs no conditions. Of course, if I want more production, I would need to use other plants with the clones, but the research is not enough to support this necessity.


Álvaro: In the Douro Valley, this is not a big problem because our soil has a good permeability. The schist  has strong narrow clefts and we used mechanize the vineyards. We do four to six treatments per year, so it’s not too many hours of tractor in the vineyards.

Mimi: I think vineyards really should be very concerned about compaction. Mostly, from the disease control. Even our organic spray programs are pulling a heavy sprayer and tractor through the vineyard multiple times per year. So compaction is a big concern for me because we don’t cultivate, we don’t plow. We really are trying to get as dense and as diverse a root system in the vineyard on the floor permanently as possible to resist that compaction.

I don’t think that it’s realistic to claim that if you’re going to be doing that many tractor passes, that you’re not going to have some compaction. I do think that as you gain some equilibrium and your biodiversity achieves a certain threshold, you can resist compaction enough so that nutrient cycling is still occurring and there’s good productivity in your soils. But plants and their associations with both above-ground animals and below-ground microorganisms are what build topsoil.

The amount of carbon and water topsoil can store, the amount of nitrogen that it can sequester; all of these things are exponential. We do have to at some point, I think, acknowledge that we’re working on geological time, sometimes, to repair these systems, and there will be challenges that we meet along the way and addressing those with.

If we feel like we have some compaction, there are things that we will seed directly into our cover that have deep root systems. A lot like what Teresa was saying with some of the graminoids, that just have really fibrous, very deep root systems and can break up compaction layers, but it takes a lot of time and effort.

We get all of our rainfall in the winter. Our summers are very Mediterranean. We get less than half an inch of rain during our growing season. We do have to time our practices and minimize compaction as much as possible, because we don’t do any plowing here. We’re not aerating soil any other way than with the plants that are growing here.


Mimi: Biochar is a very interesting potential tool because a lot of our soils, agriculturally, historically, would have burned more regularly than they’re burning now. So the carbon layer that that would have put back has been lost over time. If I were going to just put any one last point on any of these, is that carbon is really, truly unique, It is tetravalent, and so it can form so many bonds with itself and with other soil minerals and soil nutrients.

That is why when you think about adding an amendment like biochar, there is a potential for it driving your capacity to both grow organic matter and sequester more carbon because of that exponential capacity of carbon to form more and more bonds. The more carbon you have, the more carbon you can have. That is where I think a tool like biochar becomes interesting, but as straight carbon, it is going to bind a lot of soil nutrients.

If anyone out there is thinking about experimenting with biochar, I highly recommend that you inoculate it first in your compost pile so that it comes with microorganisms that will help break apart some of those bonds that it forms with nitrogen, and phosphorus, and all the other things that you want to be there and available to your plants. Because just as a straight biochar application, I think the long-term benefits are very clear, but you can have a very short-term tie-up of your nutrients that could actually be a problem for your plants in a growing season.


Cristina: I think it was very productful and we could hear your experiences and knowledge. I would like to ask each one of you to leave us with an advice, an idea for who is initiating this path of soil regenerative approach.

  • What would be the next step or advice that you would like to leave here?

Teresa: Go to the vineyard, touch the soil, touch the plant, and work. This is the first way to regenerate the soils.

Mimi: If you’re interested in working this way, it’s the work that teaches you how to do the work. I also would just like to say every time we grow our community of like-minded growers and people who are trying to work in this way, we can meet our challenges more quickly and more capably when we work together and we share our information and our knowledge.

Álvaro: The soil, it’s our diamond, no? It’s our gold. It’s limited. Everything we do in this moment will certainly reflect the next 5 or 10 years. I remember exactly 20 years ago, when I looked at my region, we looked at beautiful but dry vineyards, like a moon. In 20 years, we changed everything.

We have a strong responsibility to show our neighbors, our sons, our next generation; the soil is the most important factor to live. We talk about vineyards, but you talk about more, more things. If you want to produce a great wine, wine with a great longevity, like Port wine, of course, the climate is very important, the indigenous plants are very important, but the soil is where everything started.

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