Ξ March 5th, 2009 | → 2 Comments | ∇ A Day at a Time, International Terroirs, Interviews, Technology, Wine News, Winemakers, Wineries |
I am pleased to post the third and concluding interview on the subject of vineyard soils. Here presented are the thoughts of Peter Schmidt of Domaine Mythopia. I enjoyed a lengthy interview with the gentleman in early January. What is offered below are significant refinements, amplifications and additions to that interview. In my intro to this series I referred to Herr Schmidt as an vineyard experimenter, a somewhat clumsy phrase that nevertheless gets to the heart of his project. He works on matters of soil life enhancement through biodiversity and the judicious use of biochar so that terroir might best be expressed. Yes, he believes in terroir. And his disciplined, scientific approach to the subject will certainly be of interest to many of my readers and the wider vinous community.
Finally, it is the humility before the complexity of soil, a humility shared by Zed Rengel, Jason Lett and Peter Schmidt, that is the proper intellectual attitude. As Herr Schmidt says, “Soil is an endless science”.
Here are the links to the first two interviews:
Zed Rengel and Jason Lett.
Admin Thank you agreeing to speak with me again. My first question concerns the relation or contrast between biochar and composting as methods of carbon sequestration. Is it true that composting does add to green house gasses?
Peter Schmidt First of all I would not make the contrast between composting and biochar. For me composting and biochar is something that belongs together. They are two things that are very important for soil. So we won’t replace compost for biochar. What we’re trying is to enhance the quality of the compost through additions of biochar. When we put biochar in the soil usually we do it with compost.
With compost you get the nutrition to the soil, you get the bacteria, you get life in the soil. With the biochar you get the structure. Biochar gives a new structure to the soil. Therefore you can enhance the effectiveness of the compost.
Composting releases methane, carbon dioxide, and also nitrous oxide during its decomposition. That, in fact, is no good for sure! But if you would take from that the conclusion that you should not compost that would be wrong. The soil needs compost the same way the soil needs organic material as naturally occurs. You simply can’t take it away. In fact, this is a problem now with biogas and with the utilization of wood, people using wood pellets for heating. They take the whole tree with all the green stuff, and they scrub clean the forest floor. But you kill the forest with that because you take off all the nutrition from the soil so that the other trees, those left, will have nothing to eat.
With composting it is just the same as a natural process but a little more effective. With composting we can accelerate this process with the heating that comes with composting itself. It gets very hot in a compost heap. It goes faster than the natural process. So by proper composting methods you can control the release of methane, CO2 and NO2.
Now, coming back to biochar, we don’t use this composting process for its production, of course, but we use the same organic material that we use for composting. For biochar we use pyrolysis. The biochar machine is, in fact, situated or installed at a huge composting facility. It is an enterprise that, before they began working with us for the production of biochar, they did composting.
So, once the biochar has been produced we mix it with organic material and start the composting.
What percentage of the total mass of green waste generated from a vineyard is typically used for composting and what for biochar?
PS For the moment we test additions of one to five percent biochar to compost…. Just to finish what I started explaining, why we put biochar into compost. The compost becomes much more effective than compost alone. In fact, what we produce is a kind of terra preta. If you put only biochar into the soil you have a carbon sink and some structure but you don’t have all this bioactivity you get with the addition of compost.
Just to give you an idea, biochar has 300 m2 per gram of surface area because of its structure, (depends on the way you pyrolyse). Compost has usually 1m2 per gram surface area. Adding 0,1% of biochar increases the specific surface of the compost already to 8 – 10 m2 per gram. We are starting new compost tests now with biochar concentrations from 1 up to 20%. You get ten to twenty times more surface area inside, not outside. Or a square yard, if you prefer, with a slight recalculation.
What!? That is incredible. Could you provide me a visual aid in understanding this increase?
PS Fold a 300 m2 sheet of extremly thin paper about 1000 or 10.000 times an you get it. 300 square meters… it is incredible!
And all that additional space is available for microbial and chemical activity.
PS That’s it. That’s the point.
And of course water retention.
PS Water retention and also the retention of minerals and even toxic residues. With the increase of life space for bacteria you get hot spots of activity inside and enhance the whole life of the soil, not only bacteria but nematodes and protozoans.
Bacteria has carbon and nitrogen in its cells, of course. So when it gets eaten by fungus or nematodes C and N gets back into the soil. Plants then get their nutrition.
One often reads of the importance of vine stress in the production of high-quality grapes. Is it possible to make a vineyard soil too healthy? Microbial competition for nutrients appears to occur at the expense of the vine’s own search for requirements. One reads that microbial populations actually have to decline before a vine might take its fair share. Could you clarify this seeming paradox?
PS I wouldn’t say ‘too healthy’. For me ‘healthy’ means the soil is in balance. You can have a soil in balance with a huge bioactivity or with less bioactivity. Mineralogical structure is important, too. But, for sure, if you put a grape vine into compost and nothing else you would probably not get very good grapes. If you put corn in the same compost pile you will get a good yield. So you have to find an equilibrium, a balance. Now, you can regulate a vineyard by growing other herbs, with biodiversity between the vines. There are many possibilities available to direct the soil balance you want to have.
Yes, biodiversity. If one thinks only of mono-cropping, vines alone, the vineyard becomes more difficult to balance. This is true, yes?
PS Yes. I am sure about that. Indeed, if you put too much compost and biochar in the soil the balance may be upset. It’s like the vegetarian who eats too much; even though they always eat the best food possible they will get as fat as someone who only eats at McDonalds! (laughs) Too much added to the soil is not a good thing. The soil is spoiled.
Are there certain microbes associated specifically with the vine?
PS I don’t know. There are millions and billions of them. I don’t know if there are some species which are better than others. It would have to do with the local microbe mixture. You might well find variations between local vineyards. What you can say is that you must have mychorizzae [fungal] symbiosis with the vine’s roots. This is a fundamental relation. They exchange nutrients. The roots give sugar. The vine produces sugar through photosynthesis, but down inside the soil the mychorizzae can’t produce sugar. It has no light energy. So the vine root and the fungus do a good deed: The root gives the sugar, the mychorizzae gives back minerals the root couldn’t assimilate otherwise. With this exchange the vine gets certain kinds of minerals, phosphate and oligoelements [trace elements].
So if you want to have a terroir-driven wine, to have vines that really produce the terroir minerals in the grapes, you need this symbiosis. And one very interesting thing about biochar is that it enhances the chemical signals between root and mychorizzae to find each other. It’s like radio. Biochar plays it louder! (laughs) A healthy vineyard soil requires this symbiosis.
What is the relation between the depth of a vine root system and the application of compost and biochar with respect to terroir expression?
PS In our vineyards roots can get down to a depth of 10 meters, 15 meters. In California I’m sure you get down to 10 meters. It depends on the kind of vine but you can easily get down to 10 meters. Down there, even if it’s very dry, you get water. With water you get minerals. The most nutrition, nitrogen, phosphate, potassium etc., usually the vine gets from the upper soil, in the first meter, the first 50 centimeters. There you have the most carbon. For producing sugar, grapes, wood, the essentials of the vine, the first 50 centimeters are the most important. But without the roots getting deeper you probably won’t get as much mineral uptake, and the hydric stress would be too much. The vine would die without irrigation.
Here in California drip irrigation is not uncommon. The difficulty is that such technique encourages shallow rooting….Your thoughts?
PS If you were here I could show you, as I do when conducting guided tours of our vineyard, what happens when you put a mineral manure [chemical fertilizers] in your vineyard. The roots of the vine go down to 30 centimeters or so and then grow horizontal, and then the root comes up again because it gets nutrition from nearer the surface rather than down deeper in the soil. This phenomenon you find only with this kind of irrational agriculture. With irrigation it is the same. The roots grow back up to nearer the surface rather than down.
To have a terroir wine you would never do this. Terroir is not in the first 30 centimeters, the terroir is not in the fertilizers, not in drip irrigation. Terroir is down deep in the soil, and mychorizzae help liberate the minerals for the vine’s assimilation.
And you need the earthworm. The earthworm eats through the soil and ejects castings. Inside its stomach is an acid which makes a mixture with the argil, a clay-humus complex, an organo-mineralogic compound very important for plant nutrition, produced by the earthworm (and some other worms), and minerals. The earthworm has two functions. The first is to turn and re-turn the earth. Through such turning it mixes the soil elements, the char, the argil, and humus with minerals. This mixing is very important, otherwise the plant could not assimilate as well what the soil may provide, the nutrition and the elements.
Too much pesticide into the soil will eliminate earthworms. Usually you should have 1000 earthworms per cubic meter. For a vineyard worker, they should take a shovel or a spade. You can only make good wine with a spade! Only then can you see what is happening in the soil. When I do consulting I take a spade and look into the soil. When I don’t find earthworms that is already a bad sign.
What about tractors and soil compaction?
PS In our agriculture we need tractors. We try to use machines that are not too heavy, that have more tires, are wider…. Sorry to come back to earthworms and their activity, but with them you get a soil that is not as compacted. And you get oxygen to the soil. If you have oxygen you have breathing; you get bacteria that are aerobic, not anaerobic. If you have anaerobes you get methane and other toxic gasses (but no N20 which is produced close to the surface and needs oxygen).
This whole process is very, very complicated! And if I’ve explained just a little bit in the last half hour you should not think that I know very much about it. I know just a little bit. Not many people know a lot! It is an endless science. Soil is an endless science. And we, collectively, don’t know much about it. But the more we learn the better will be our agriculture. Then we can work with natural processes to improve how crops are grown.
Delightful, Peter. Is there anything you’d like to add that we haven’t at least touched upon?
PS In your email you mentioned aromatic profiles and biochar. We do aromatic profiles in our project. We take aromatic profiles from wine and grapes. We are looking at the development of these aromatic profiles through the utilization of biochar or not. It will take about three to five years, at least, until we can say something, if there is an aromatic change. For the moment we don’t know. We can’t say nothing will happen to the wine.
What we attempt is to get more terroir through biochar because we enhance the bioactivity and the balance of the soil. But what could happen if you use too much, you could destroy your results. You could unbalance the soil. This is what we hope to learn with our project.
But we don’t add biochar every year. You can’t add it endlessly into your vineyard. If you are only looking for a carbon sink then it is best to put biochar deep inside the soil and forget about it. You always have to distinguish these two uses of biochar, for agricultural enhancement and for a carbon sink.
Lastly, with biochar you can fix pesticide residues. This is very important for vineyards with a ‘history’. In Europe we have very old vineyards that in the sixties and seventies used pesticides, organochloric pesticides. They are still inside the soil. Even 40 years later you find them. They are still active. They are persistent. We’ve done experiments that showed you could fix pesticides with biochar. We’ve since extended our research to copper and to other products used as pesticides in organic farming.
We’ll see what develops.
Thank you, Peter.
PS Thank you, Ken.