You haven’t heard of biochar? You’re not alone, as Alex Russan explains.
A lot of viticulturists are talking about biochar these days but most people haven’t a clue what it even is.
Biochar is a soil amendment that is gaining popularity in agriculture, though it remains on the cutting edge in viticulture. It’s essentially pulverized charcoal. It has the ability to build organic matter in poor or depleted soils, boost microbial populations and lower a vineyard’s need for nutrient and water inputs – allowing for less human intervention, as well as lowering both grower’s cost of production and carbon footprint. This means healthier soils, healthier vines, healthier environment, and happier grower.
Biochar is made by charring plant material in a low enough oxygen environment that it does not turn to ash, a process called pyrolysis. As Josiah Hunt, CEO of Pacific Biochar in Santa Rosa, California, describes: “The resulting material has a tremendous surface area for its size, and as its adhesive surface bonds with charged ions, it can retain impressive amounts of nutrients from environmental loss, while allowing them to be biologically available. Biochar is also extremely porous, which imparts a sponge-like ability to keep water in topsoil and to be a home and safe haven for microbial populations.”
It’s also extremely stable; biochar will remain in active in soil for thousands of years. Because of this stability, it’s a great way to sequester carbon – not only its own carbon, but the additional CO2 it can pull from the air when soil conditions are improved. It also creates strong bonds with contaminant metals in soils, helping preclude their ending up in water sources or produce. It’s a very eco-friendly and versatile soil amendment.
Origins
Biochar as a human soil additive has occurred in many parts of the world, but it is most associated with the Amazon, where it is known as “terra preta do Indio” (Indians’ black earth). Although the Amazon appears lush, it has extremely poor soils, and is only able to survive from the constant recycling of its plant life (which is why Amazon deforestation causes permanent damage). Biochar-enriched soils are thought to cover swaths of the Amazon the size of France and to have allowed historic populations to flourish there with these otherwise poor soils.
Hunt quickly points out: “The word biochar is pretty new, but the material is not.” Despite commonly being considered a human-made soil additive, he says “biochar exists wherever fire and plant life happen together”.
Organic boost
In viticulture, biochar is primarily used in low organic matter soils, which usually means one of two scenarios: highly sandy soils and soils that have lost organic matter to years of conventional farming abuse.
Doug Beck is the science officer for Monterey Pacific, a vineyard management company in Soledad, California, managing more than 13,000 acres of vineyards on California’s sandy Central Coast. In a former life he was the soil scientist for the UN’s International Center for Tropical Agriculture in Colombia (and has seen the famed terra preta himself). He explains why having sufficient organic matter is important: “When you have less than 1 percent organic matter, it means the vineyard isn’t functioning on its own. You add nutrients as needed in a very mechanical way, but they are not retained in the soil and microbial populations are low. You can produce good quality grapes this way, but when you have higher organic carbon and microbial biomass, the site can function better on its own – you can add less [water, compost, fertilizer], and the vineyard will resolve disease problems better.”
© Bedrock Wine Company
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Beck notes that while soils on California’s North Coast can have around 2 percent organic matter, the sandy soils he works with on the Central Coast often have only 0.8 percent. “You have to manage these depleted soils much more than soils with more organic matter, which largely take care of themselves.” As an example of biochar’s water-holding effects (directly, and indirectly from the organic matter it facilitates), on sandy soils treated with biochar, Doug is often able to wait a month or two further into the season before starting irrigation – a big deal in drought-ridden California.
Depleted, abused soils are another way a soil can end up with low organic matter. Jake Neustadt, the vineyard manager for Bedrock Wine Company in Sonoma, California, explains: “We take over a lot of old vine sites that have been mistreated for decades, in terms of over cultivation and striping of organic matter. The farmers may have been disking four times per year, and on sloping vineyards, all the topsoil has slid to the bottom of the hill. In those sites you have very little organic matter.”
Bedrock started using biochar about seven years ago when rehabilitating abused vineyards. “The biggest thing for us in rehabilitating a vineyard, before we see a change in the vines themselves, is establishing a healthy cover crop. With biochar, suddenly the soil retains everything better (nutrients, microbes, water), so we see a big increase in cover crop biomass pretty immediately. This is the jolt that makes everything happen.”
This “jolt” ushers in a cascade of changes. At first, biochar simply retains what cover crops need to grow. The roots of cover crops feed soil microbes and the biochar becomes a home to them, increasing populations and therefore a soil’s ability to recycle plant material and furthering nutrient retention. These nutrients later feed future cover crops and the vines. Cover crops also open up compacted soils – a common occurrence in abused vineyards – allowing deeper water penetration and soil aeration, both critical for a healthy vineyard. Healthier soils and more abundant cover crops bring more beneficial insects. The vineyard gets closer to a self sustaining, closer-to-natural state.
Biochar and terroir
Biochar lasts for millennia and changes the characteristics of a soil – does it therefore alter terroir? Randall Grahm of Bonny Doon, a man who has spent much time mulling over the nature of terroir and who has experimented with biochar himself, has valuable thoughts on this. “It is changing terroir, but everything you touch on the land, every time you do anything [such as fertilizing, watering, adding cover crops, planting vines] is changing terroir. Plowing or disking is a great deformation of terroir. Biochar is a benign one. Because you’re encouraging mycorrhizae [the most critical group in the soil microbiome, which actively transport micronutrients in soil to roots], you’re enhancing the signal of terroir.” In this sense, Grahm feels biochar is a terroir amplifier, rather than a terroir deformer.
For his experimental Popelouchum vineyard in San Juan Bautista, Grahm applied biochar prior to planting. The vineyard is located on the edge of where dry farming is possible in California, and one of his hopes in using biochar is that it will allow him to dry farm. From a terroir perspective, this seems like a great deal. If all changes to a site deform terroir, Grahm is trading the application of a benign terroir deformer (and potential terroir enhancer) to gain full access to a very important aspect of terroir: enabling the vintage to be guided entirely by rainfall, as opposed to human irrigation choices.
Grahm points out that, in California, “we don’t have soils that are rich in available minerals; they’re very eroded. Especially in sandy soils, biochar is great in enhancing the uptake of minerals. If you look at Switzerland, there’s a lot of rock that is currently being eroded and released into the soil solution, biochar doesn’t have such a significant impact there. In California, with both mineral deficiency and drought, it’s particularly beneficial for our conditions.”
Biochar is a promising soil additive for many reasons. For farmers, it can lower costs. For purists, it can lower human intervention in vineyards. For the ecologically minded, it’s a great way to sequester carbon and reduce waste, as well as clean up soils and our atmosphere.
And for those interested in great wine, as organics and conscientious viticulture become more prevalent, few would argue with the idea that healthy, happy vineyards make better wine.
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