Season 3 | Episode 13: Hidden Drivers of Vineyard Nutrition

00:00 Patty Skinkis

This is the Hi-Res Vineyard Nutrition Podcast Series, devoted to helping the grape and wine industry understand more about how to monitor and manage vineyard health through grapevine nutrition research. I am your host, Dr. Patty Skinkis, Professor and Viticulture Extension Specialist at Oregon State University.

00:23 Patty Skinkis

Vineyard nutrient management requires a long-term approach. Grape vines are perennials and what happens in one year or over a series of years can impact vine growth, nutrient status, yield, and fruit composition. Good data collection and historical information is important to consider in the context of making nutrient management plans in the long term, but we cannot forget about documenting our management practices that may have a big impact. While traditional grapevine nutrition research studies are conducted using controlled fertilization trials aimed at determining nutrient thresholds linked to vine responses such as vine growth and yield, there are many other research studies that show how management practices influence vine performance that is linked to nutrient status. Such studies are often the most helpful for grape growers to understand what to expect from their management practices and what they may need to add back into the vineyard from a nutrient standpoint. This may be accomplished directly through fertilizers or through other input means such as cover cropping, tillage, or organic amendments.

Today's podcast features Dr. Thibaut Verdenal for a discussion of viticultural practices and how they impact vine nutrient status and vine physiology. Dr. Verdenal is a technical scientist at the Agroscope Research Station in Pully, Switzerland, where he has spent the past 17 years working on applied viticulture research to serve the needs of the Swiss wine grape industry.

His research evaluates whole plant physiological responses in the context of viticultural practices and environment. He has published many studies on canopy management practices such as basal or cluster zone leaf removal, crop thinning, hedging, and has conducted research on cover cropping and connected that with vineyard nutrition and vine nutrient management.

Welcome, Dr. Verdenal.

02:18 Thibaut Verdenal

Hi, Patty. Thank you for having me.

02:20 Patty Skinkis

You are conducting really great applied viticulture research on vine balance and how this impacts vineyard nutrition in a temperate viticultural region. Your work on crop load management and the impacts on vine nutrient status is of particular interest for the team on the Hi-Res Vineyard Nutrition Project, but also our listeners who are in the US grape and wine industry.

To start out with, I'd like you to tell us a little bit about where you work and how you connect with the Swiss wine grape industry.

02:52 Thibaut Verdenal

Sure. I work in Switzerland. I work for the Agroscope, which is a federal research station in agriculture. And I'm part of the viticulture team. We do mostly applied research for the for the Swiss vineyard.

03:08 Patty Skinkis

Tell us a little bit about, you know, what is the size of the Swiss wine grape industry in terms of acreage and wine production or varieties of interest.

03:17 Thibaut Verdenal

Switzerland is a very small country, but its vineyards are proportionally big, actually. It's about 15,000 hectares. And we grow mainly Pinot Noir, Merlot, and Gamay for the red varieties and Chasselas for the white variety. We are also very proud of our local and unique varieties, such as Gamaret, Garanoir, Humagne Rouge, or Petit Arvine. The wine consumption, the wine culture is really part of the Swiss life. Since we are in Europe also, our neighbors are France, Italy. We are very much into wine. Actually, the wine consumption in Switzerland is quite high. It's about 32 liters per year per capita. And I took the numbers for the US, it's about 12 liters, just for a comparison.

04:16 Patty Skinkis

So about half. One of the things that I heard once before from our project director, Marcus Keller, who is Swiss – he said that majority of Swiss wines never leave Switzerland because it all gets consumed there. Is that correct?

04:30 Thibaut Verdenal

Yeah, that's right actually, the production of wine is not sufficient to cover the Swiss consumption. Actually, in three bottles consumed in Switzerland, two or four from abroad are imported wine.

04:45 Patty Skinkis

Wow. We need to translate that culture here to the United States this moment. Very, very concerned about declining wine production or wine consumption in the United States.

Well, what are the primary challenges that growers in your area face with respect to vineyard management?

05:00 Thibaut Verdenal

You have to know that Switzerland is covered mostly by mountains. So, we have lot of steep slope vineyards and the plots are very small. Actually, the winery sizes are quite small. On average, it's below 10 hectares per winery. It's steep slope and quite difficult to mechanize. So, the production costs are quite high. And on top of that, we have the competition from abroad. So, to maintain our industry alive, we have to produce high quality wine.

05:38 Patty Skinkis

Sure. So lots of inputs I'm imagining because of the climate, the conditions are such that there's high vegetative vigor. Is that correct?

05:47 Thibaut Verdenal

I would say that the conditions have changed over the last decades. In the 80s, we used to have very dense plantation, high production, high vigor. And with the time, our practices changed. You want me to develop that a little bit?

06:08 Patty Skinkis

Sure, yeah. Can you describe some of those changes?

06:09 Thibaut Verdenal

Yeah. The thing is in Vättis, we faced a period of overproduction, so we started to do cluster thinning for several reasons. To improve grape ripening, to reduce the fungal diseases, and to reduce the production quantity. And by doing that, we thought, OK, maybe we should reduce the density of plantations. So we started to plant in a lower density.

And from that, we started to mechanize more and to change the floor management too. So we started to use more cover crop also to reduce erosion because of the steep slope, to bring more organic matter in the soil. So all those conditions lead it to a lower vigor in general in the vineyard.

07:01 Patty Skinkis

No, that's perfect. And in terms of that time shift, you said it was over the last decade or so that those changes have been made?

07:09 Thibaut Verdenal

Last few decades, yeah, it started in in the eighties. But as soon as the 90s, we started to point out defects in the wines, particularly white wines, showing some less aromas and more astringency and bitterness in the mouth and through our studies we pointed out that it was mostly related to the nitrogen concentration in the must at harvest, the YAN.

07:38 Patty Skinkis

Did you ever see that quality in the Pinot Noir over that time frame from having a kind of “off” aroma or flavor as a result of maybe what might be considered plant stress?

07:51 Thibaut Verdenal

For the red wines, we also observed the lower quality of the wine. [It is] very low, actually, the level of nitrogen required for to make the wine, red wine, are lower than for white wine. But still, if it's not enough nitrogen, we have seen in the red wine that the tannins, the concentration is okay, but they are more dry astringent. And the potential of aging is lower. So in the end, the appreciation, the global appreciation of the wine is less.

08:26 Patty Skinkis

We've seen some of that similar shift here in Oregon with practices and then, I hesitate to call what the industry has called the “stressed vine syndrome.” And it's been for red wines, well, particularly Pinot Noir, and for us to put our finger on it has been very difficult, but we associated that possibly with dropping YANs as well. So yeah, interesting.

9:00 Thibaut Verdenal

In Switzerland, we pointed out that problem mainly on the white wines, especially Chesslas, which is very sensitive to nitrogen deficiency.

10:13 Patty Skinkis

Interesting. So, given this background and what's been happening over time and over, you know, even your career at Agroscope, can you talk about some of the research that you did to and with cluster thinning and leaf removal?

I know those weren't necessarily done to impact vine nutrition, but how did those practices shift the vine nutrient status, or did they at all?

9:23 Thibaut Verdenal

Yes, sure. We did the terroir studies, like based on the network of plots everywhere in different regions. And from those studies, we were able to point out that the main component in the must at harvest related to the wine quality is not the sugar level or the acidity or the balance of the two. It was nitrogen. We made wines from different plots in our winery, and it was always the same plots that were giving those the best wines, and always the same plots that were giving to the worst wines. So with that, we were able to point out that, so the relation to the nitrogen, and after that we wanted to understand what influenced the nitrogen level in the clusters. And through those studies, we were able to point out the huge influence of the vintage, the climate conditions. So the level of nitrogen can change from single to double, then between two years.

That impact is unpredictable. We don't know what climate will have next year. The second factor of influence is the soil. The soil is very much related to the plot, so it doesn't change. This impact is the same every year. We always obtain the highest nitrogen content from the same plot. It was regular, okay? Only after that, we were able to point out the impact of our practices, whichever they were, like soil management, fertilization. So, it was a smaller impact compared to the environmental conditions. Our work was to understand the influence of the environmental conditions and to adjust our practical techniques to adjust and optimize nitrogen given the environmental conditions.

Do you follow me?

11:22 Patty Skinkis

It makes complete sense.

11:25 Thibaut Verdenal

From that, we wanted to promote integrated viticulture. So, when we are facing a nitrogen deficiency, we don't go straight for fertilization. First, we need to adjust other parameters. We usually say that we have four major parameters to manage nitrogen nutrition. First is the choice of the plant, like the genetics, the variety you choose, the rootstock you choose, and the combination of the two. That is a long-term decision that you do before plantation. If that choice is not correct, then we have to face the problem for the next 10, 20 years. The second point is the soil, the management of the soil. Do we go for cover crops? Do we till? We have to keep in mind that cover crops is a source of competition. It’s another plant in the vineyard that will be in competition for water and nutrients. We have to keep in mind. In some vineyards, it's okay. The soil is deep enough. The organic matter is sufficient. It's not too much of a problem. But in other situations, steeper slope, very shallow soil with lower water amount, it can be a very big problem. The third point is the balance of the plant. That’s actually – I have many results about that. How to manage the balance between the leaf area and the fruit load.

So there is two ways to manage the leaf to fruit ratio. Either you manage the canopy, the canopy height, or you remove the leaves, or you remove clusters. You do cluster thinning. By doing the two, you don't get the same results. That is a very important thing to have in mind. We realized studies that when we change the canopy height, the trimming height, we went from 60 centimeters to 140 centimeters. We realized with the same foot load, and we realized that when you have a lower canopy high, you have a higher concentration of YAN in the clusters, in the grapes at harvest. Okay? So that was a very interesting result, and it's a quite big variation, actually. It means that we shouldn't have too many leaves. It's useless.

The leaf-to-fruit ratio is important to guarantee grape ripening. And usually in our condition in Switzerland, we grow the grapevine in our Guyot system, and we recommend usually 1.2 square meter of leaves per kg of fruit. Above that, it's useless. You don't improve the ripening anymore, and you may induce nitrogen deficiency in the grapes. But if the leaf-to-fruit ratio is too low, then you might not guarantee the grape ripening. You have a better nitrogen concentration, but ripening is not good every year. So that was the main result of that of that study. So that is if you manage the canopy size. And now if you do cluster thinning, so that – I completed my PhD on that subject few years back. That is very interesting too, and the results are very different. So the cluster thinning will affect the entire cycle of nitrogen in the grapevine. By that, I mean the nitrogen uptake, the distribution into the plant, the filling of the reserves, and the reuse of the in the following year. All that is affected by cluster thinning. In that project, we have two groups of vine, or one low yield condition and one under high yield condition. And to just to make it simple, I would say that in under high yield condition, we had better use of nitrogen, higher uptake from the soil and from the fertilization. But sometimes ripening was difficult. And on the other conditions, under low yield conditions, the fertilization was less efficient because the grapevine, the demand from the grapes is lower. There is less grapes. The demand is lower. So the vine just slowed down. The activity is reduced. Photosynthesis activity is reduced too. and nitrogen uptake is lower. So we reduce the entire quantity of nitrogen in the plant. We don't increase nitrogen concentration in the must at harvest. That is a very quantitative result.

But on the other hand, the storage of nitrogen in the reserves, in the perennial parts, in the roots, is better for the next year.

16:34 Patty Skinkis

That's really an interesting finding, because like you said, they're almost contradictory of what you would expect. But I understand completely, because I've done yield trials and thinning trials myself, but we were more on the low end. We were working in the operation parameters of what growers do, and we were reducing it further. And we saw the same thing, that basically reducing crop if we already are doing crop management did not lead to a change of YAN in our fruit or even in the vine tissues. So, if we looked at leaf blades and petioles at veraison. But for context, can you give us some sort of parameter as to what the high yield was in terms of how high it was and the what the low yield was, whether it's kilograms per meter or um what was the magnitude of the high and the low?

17:20 Thibaut Verdenal

Yeah, the range of yield varied from 0.5 kg per square meter up to 4.5 kg, so very high.

The experiment was on Chesslas, and Chesslas is a very productive variety. So, we managed the yield by cluster thinning. But the point, the conclusion on that study also is that we potentially, we should adjust fertilization to the yield. That is very important.

17:55 Patty Skinkis

Absolutely. Cluster thinning. I like the fact that you talk about the two management zones of the canopy versus the fruit having different impacts. That was very interesting. You said there is a fourth – you said of the four things that you manage when you have low end, there's the variety or rootstock. You've got your soil management practices. You've got your vine balance of the plant. What is the fourth thing that you mentioned?

18:22 Thibaut Verdenal

The fourth one is fertilization.

18:23 Patty Skinkis

That makes sense.

18:25 Thibaut Verdenal

Yeah. It's all the inputs, actually. The irrigation as well. When I speak about integrated viticulture, I mean that we want to reduce the input to the maximum, to the minimum, mind I mean. And for that, we need to adjust all the parameters before thinking of adding something. We have results also on fertilization efficiency. We work on that too.

18:52 Patty Skinkis

That's great. I like that, the integrative viticulture where you're taking into account all of the pieces of the equation and not just going to that quick fix answer. In terms of all those studies that you've done where you've looked at the canopy and trying to support that idea of adjusting vine balance and putting some real numbers to it, it's great to hear some that you've done that work because that can be challenging.

Let's shift to some of the work that you've done on looking at cover cropping and the vineyard floor management studies. As you mentioned earlier, there's been this shift in Swiss vineyards and how they've managed and how they've led to a decline in nitrogen and specifically in the YAN, which was picked up in the wine quality.

Can you speak a little bit more about how this shift on vineyard floor practices or how the soil is managed? Can you talk a little bit about what those changes have been over maybe the last 10 years or the last decade?

19:52 Thibaut Verdenal

Yeah, sure. I would say over 2030 last year, yeah, before we used to have bare soils, okay? We used a lot of chemicals, weed killers. And little by little, we started to use cover crops. At the beginning, we did it little by little, okay? For example, at the beginning, we started to put cover crops one row in two, okay? A maximum 50% of the soil was covered. But with time, I guess the mind changed as well. And now we are more like, we use much more cover crop. The standard I would say now, especially in the Geneva region, we have grass in every row. We maintain below the row, we maintain clear. We work on the ground. We can use a weed killer or we work the ground mechanically. But sometimes we can see also vineyards 100% covered. So that's a very intense cover crop, actually, and the competition is in those situations is quite high.

21:04 Patty Skinkis

So, the competition is really high. You said they're mostly grasses. Do you see incorporation of other kinds of cover crops that might supply nitrogen, like legumes? Or do you see predominantly grass species?

21:19 Thibaut Verdenal

In our region, there are different kind of weeds coming naturally, and legumes are part of it. But we did studies also to compare different kind of grass and legumes and see the advantage and disadvantage because we were thinking of installing our own cover crop, you know, not letting the natural one to develop. And we did trial to compare legumes with, ryegrass. So the thing is, depending on the and the variety, the competition is different. Legumes can be nice because it will catch nitrogen from the atmosphere and release it after destruction of the legumes. But the other side is that it's quite high consumption of water. And we pointed out that the water competition can be a problem too.

22:17 Patty Skinkis

And in your region, are most vineyards dry farmed or do you have some combination of dry farming and irrigation based on soil type or in depth?

22:27 Thibaut Verdenal

Yeah. Under our climate, irrigation is not a common practice. We do see it more and more. Following those last years that were quite hot and the climate demand was higher. But still today, it's not common practice.

22:42 Patty Skinkis

Most of these practices you mentioned that there's reduction in herbicide. Would you say that more people are doing under vine tillage of some sort for weed control versus herbicide use?

22:56 Thibaut Verdenal

Yes, in the vineyard where mechanization is possible, today exists many tools to maintain the ground below the wall. So that's very nice, actually. And we can do very clean work without chemicals. But our problem in our situation in Switzerland is the vineyards that are in steep slope situation and mechanization is not possible. And that actually, we have to manage the wheat by hand.

So that's tough work. So, we are still looking for a solution. We are trying different mixes of varieties to reduce the competition of cover crops.

23:34 Patty Skinkis

One question I have with respect to a lot of this is back to the rootstock. What rootstocks are grown in the region or used in the region? And have you seen a shift in rootstocks to this point.

23:46 Thibaut Verdenal

The most common rootstock that we use is 3309 – this is the most common in Switzerland right now. We have trials going on trying different rootstocks trying to reduce the water deficiency, but that is a different subject.

24:09 Patty Skinkis

Yeah, so that natural shift towards possibly changing future design of vineyards with plant materials to address water scarcity and possibly this declining nitrogen. Yeah, so we use a lot of 3309 as well here in Oregon and across the United States. So, lots of 3309. Maybe not in California, but a lot of other areas in the United States. This is interesting, and, you know, a lot of the shift towards no-till, lots of cover crop use, undisturbed soil, no herbicide use is becoming very popular here in the United States. Specifically, I can speak from Oregon perspective, even in outreach to the industry this winter and early spring for focus group meetings, what came up repeatedly is that growers are wanting to do less intervention. So not tilling as much, using cover cropping, reducing herbicide use. And a lot of that is here in the United States is not regulation-driven. It's mostly people wanting to not use chemicals. Using farming philosophies that are either in the realm of organic or biodynamic or regenerative. So a lot of shifts towards regenerative agriculture here in the United States.

Are you seeing some of the same pressures from either society or just among the farming community to do some of those less intervention? Is that what's driving some of these practice changes?

25:36 Thibaut Verdenal

Yeah, I think so, it's a global change in the way of production. But I would say that that is not a problem, but we need to adjust our way of production to that. And for example, if I come back on fertilization, we are trying to improve fertilization efficiency given the context of cover crops. Because that we pointed out that fertilization to put, for example, nitrogen on the cover crops, this is not efficient at all. The grapevine doesn't get the nitrogen at all. And that we pointed that out. So we give different advice. I don't know if you want me to develop a little bit on that.

26:21 Patty Skinkis

Yeah, actually, that leads very well into my next question is with the foliar nitrogen work you've done and published some of that work. If you could talk about kind of the work you did with foliar applications and what you saw there.

26:34 Thibaut Verdenal

About foliar application, we recommend a late application veraison. The way we recommend fertilization is that we recommend soil fertilization at springtime before flowering, and foliar application later at veraison. If required, if we see that there is a nitrogen deficiency present, then we advise foliar application. Usually we recommend up to 20 kg per hectare of foliar application on the entire canopy at veraison.

We tested also the area of application, because that was a simple question from a producer. Since we want to concentrate nitrogen in the clusters, this is the purpose of the late application at veraison, the foliar application is mostly to concentrate nitrogen in the cluster to help to improve the YAN concentration. That question was, shall we apply it on the entire canopy or on the cluster zone? So we did a small trial, very practical trial. So we on the one hand, we applied only on the cluster zone. On the other hand, we applied on the entire canopy. And we realized that the results were equivalent. So both ways worked. But by concentrating the same quantity of the area in the smaller zone of canopy, we add more symptoms of toxicity due to excessive ammonium, temporary excessive ammonium. So finally, we recommend to spread on the entire canopy.

28:19 Patty Skinkis

That's interesting. Do you use the same concentration or you adjusted concentration?

28:24 Thibaut Verdenal

Yes, it was the same quantity of nitrogen applied either on the entire canopy or concentrated on a smaller area. Actually, those 20 kg, we recommend to apply them split in several times, 5 kg every time. Above that, we risk toxicity symptoms on the leaves.

28:44 Patty Skinkis

So, when we're talking about this, where the goal is to increase YAN. Specifically, can you speak to kind of what ranges of YAN you were seeing and when you were getting into these deficiency stages? And with those applications of the foliar nitrogen, what was the improvement that you could see?

29:03 Thibaut Verdenal

The efficiency of the foliar application is very variable, okay? It's an efficient method, but variable. So, like I said before, the fertilization efficiency is related also to the yield, so that there is an impact on that. If the plant is very weak, and the deficiency is very strong, then the nitrogen uptake will be less. That is a point. Actually, I could tell the numbers about that study, in average, nitrogen uptake is about 30%. Only 30% of the nitrogen we applied is actually taken up by the plant. And if we reduce the yield, then yeah the quantity of nitrogen assimilated is only 25%. So the efficiency of fertilization is lower. Then there is the impact of the climate. So that that is very important from year to year. But if I take in average, usually we consider that we are under deficiency below 140 milligram per liter of YAN in the must at harvest. And quite often we can see that after foliar application, we gain 50 milligrams. We can gain 50 up to 60 milligrams of YAN per liter of must when it's efficient.

30:36 Patty Skinkis

Okay. That's really helpful to see.

30:39 Thibaut Verdenal

And this is with urea. So I mentioned that because I know that urea, at least in Europe, is forbidden for organic farming, organic viticulture. So in that condition, you need to use other kinds of fertilizer, foliar fertilizer. But till today, we didn't find any product that is as efficient as urea, as cheap and as efficient.

31:06 Patty Skinkis

Yeah that’s interesting because that the number question that we get, at least here in Oregon. They want to fix the nitrogen and the YAN in organic vineyards. That’s what we found too, is that there is not a foliar application that is working.

So, from those studies do you see many growers applying some of these practices? I’m kind of trying to shift gears to the findings of adjusting crop yields or adjusting canopy size or doing some of the vineyard floor changes. Are you seeing changes in what growers are doing and seeing success with improving the nitrogen numbers?

31:44 Thibaut Verdenal

Yes, sure. For example, about fertilization efficiency, we recommend to locate the nitrogen supply below the row. The same quantity of nitrogen, instead of spreading on the entire vineyard, you locate it and you localize it below the row. And that increased the efficiency of fertilization. And that, I could say that it's now into practice. Foliar fertilization also, that is a recommendation that that we do. And in contrast to soil application at springtime, which builds vigor and the reserve of the plant and the maintenance of the long term, foliar fertilization is really to increase YAN at harvest, and this is into the practice also. It's a good reflex for the producers.

Yeah, right now we are working a lot on cover crops, and the producers are quite aware now of the danger of the presence of the competitions of the cover crop and that we need to adjust and control and limit the development of cover crop to limit also the nitrogen deficiency. And maybe there is one more thing that I didn't speak so far. It's about YAN analysis. That for a long time, it was not into the routine analysis, but I'm convinced this is one of the best ways to monitor the nitrogen nutrition into the plant. And also it make a link with the must and the wine, the vinification. So I think this is the most important parameter to measure, to have a good view on the nitrogen nutrition of the plant.

33:37 Patty Skinkis

So, are the YAN measures that are happening, are those being done in house by wineries or is it happening by service labs, are people sending samples pre harvest to detect YAN or watching that migration of YAN over time?

33.00 Thibaut Verdenal

Yeah, we have service labs to do that most of the time.

34:00 Patty Skinkis

Yes, we have similar here as well. So, in terms of the other parameters that people look at for vineyard nutrition, I know some of your work has pointed to nitrogen sensors, visual observations. Can you speak a little bit about how growers keep an eye on vineyard nutrition, whether it’s nitrogen or other nutrients.

34:22 Thibaut Verdenal

First of all, we recommend a good observation of the plant. That is the first to do, the cheapest and the simplest. After that, we have for nitrogen, it's possible to use a chlorophyll index. So that's a small machine, quite affordable. You can measure it, it's non-destructive sampling and you can do nitrogen monitoring during the season. Actually, we propose tables to for interpretation at veraison. And sometimes producers, they can go for leaf analysis. We recommend to do it at veraison because the nutrient level is more stable at that stage. The leaf is grown, already is developed, so there is less variation. And we propose tables as well for interpretation. There is the YAN also in the must at harvest. And more recently, we published some results about measuring the YAN at veraison.

So very early, very early in the season. And the interest here is that we noticed there is a very good correlation between the YAN concentration at veraison and the YAN concentration at harvest, with differences between varieties. For example, for the Chesslas, the YAN at harvest was usually lower than YAN at veraison, a little bit.

But for Pinot Noir, for example, it was approximately the same. So it could be, and the correlation is quite high, so it could be a good tool to measure the YAN in the grapes before just before veraison, to have an idea of the nitrogen level. And if it's too low, maybe it's still time to go for foliar application with the idea to help the YAN concentration at harvest. So that is not in the in the practice yet, but that could be developed potentially.

36:29 Patty Skinkis

Interesting. That’s great. You addressed a couple of my questions, whether there are nutrient guidelines that growers follow, and it sounds like you have those created for growers to use. So how do you typically share this information with growers? You know here in the United States we have extension publications, and we have those available for growers kind of as fact sheets that we share with them or bulletins. Do you do the same there? Or how do they figure out the information they need?

36:57 Thibaut Verdenal

Yeah, we publish regularly. For example, on the website, we have a review that is online. It's open access. It's Recherche Agronomie Suisse. And there, we publish most of our results. And then we also publish technical sheets where they can find the tables. And we communicate a lot also. We do presentations. Most of our trials are managed until vinification. So, we are able to organize blind testing, discuss about the wine, and then explain what are the factors that influence the quality of the wine.

So that is very nice to speak with the producers, because when you test the wine, then it's more concrete, you know, sometimes it's difficult to believe, and then especially to speak about nitrogen deficiency, to test wine that is nitrogen deficient, that after that, you know how to recognize it.

37:57 Patty Skinkis

So some training went on to recognize some of those issues in the wine. I also noted in your information that you are responsible for micro vinification. So you take all of your trials and do all of the vinifications yourself?

38:14 Thibaut Verdenal

No, not all of them. We have a winery, especially for the trial with the replicate and everything. So, most of our trials are managed in this winery. And this is the Enology team who takes care of all those microvinifications. On my side, I do the microvinification in the context of grape breeding and the selection of new varieties resistant to fungal diseases. I do the pre-screening of the new variety, we test immediately if there is good potential for wine. So, in that context, I manage about 180 microvinifications, and it's on average 10 liters per vinification.

39:01 Patty Skinkis

Wow. Busy, busy.

39:03 Thibaut Verdenal

Yeah.

39:04 Patty Skinkis

This is great information; we have covered a lot of different areas in the work that you have been doing. And I guess one of the things that I want to do to wrap up is, when we think of all the work that you have done on vineyard nutrition and crop size and canopy size and vineyard floor management, what is one thing you want to leave us with today that the listeners can take away that you want them to know about vineyard nutrient management?

39:32 Thibaut Verdenal

Just one thing?

39:34 Patty Skinkis

Well, you can do two.

39:36 Thibaut Verdenal

So maybe just to speak about cover crops. We shouldn't underestimate the impact of the presence of cover crops in the vineyard and the impact on nitrogen nutrition of grapevines. That is one of the major points that I could say. And the other point is that nitrogen management should be done over several years. We should manage nitrogen nutrition thinking of the practices that have been done the year before and having in mind the needs of refilling the reserve for the following years. Because whatever we do has an impact on the following years. So, if we have a more integrated view of nitrogen nutrition, that would be for the best.

40:27 Patty Skinkis

I like that, that is great. Great take aways to think about. On longer term nutrient management and especially as we start to see more vineyards turning to that approach of doing less, but we still need to do something. We need to monitor and manage according.

Well, thank you so much for agreeing to be here on this podcast and sharing your information. I’m going to include a number of links to your publication and Agroscope to the show notes so that listeners can find out more about what you do. Thank you again for joining us, and if you would like to learn more about the Hi-Res Vineyard Nutrition Project, you can look up our website at highresvineyardnutrition.com.

Show notes and links:

Learn more about the

• Hi-Res Vineyard Nutrition Project
• Agroscope Research Centre in Pully.
• Thibaut Verdenal’s published research.

Related podcast episodes:

• Season 1, Episode 11 | Vineyard to Winery – Looking Beyond YAN (Amanda Stewart)
• Season 2, Episode 9 | Does Vineyard Nutrition Impact Wine Sensory? (Megan Mershon)
• Season 2, Episode 10 | Tracing Nitrogen from Vine to Berry (Pierre Davadant)
• Season 3, Episode 3 | Interesting and Unexpected Wine Outcomes from Nutrient Trials (Jim Harbertson)

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This podcast was funded through the National Institute of Food and Agriculture’s (NIFA) Specialty Crop Research Initiative Coordinated Agricultural Projects (CAP) grant. Project Award Number: 2020-51181-32159. The continued efforts of the podcast are funded by the Viticulture Extension Program at Oregon State University.

Audio mixed by John Adams.