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O'Neill Vintners & Distillers' Trial on Regenerative Organic Viticulture Led to Better Soil Health, Slight Yield Increase
by Katherine Martine
For B Corp certified O’Neill Vintners & Distillers, sustainable growing practices, building a sustainable future and being a force for good is top of mind; The company has taken that a step further with a recent transition and expansion to regenerative organic farming as part of a three year trial comparing regenerative organic viticulture to conventional viticulture, and a pending Regenerative Organic Certified (ROC) certification.
In an Aug. 29 webinar with Agrology, O’Neill shared insightful data that makes a strong case for adapting regenerative organic viticulture: Not only was there an initial slight yield increase in the 43-acre regenerative farmed block, but there was also increased water holding capacity, better plant respiration, cooler canopy temperatures, increased CO2 absorption and better conditions for soil microbes, tiny yet important creatures that help improve soil health.
The trial, launched in 2020, aimed to understand regenerative organic farming practices and its effect on grape yield, soil health, quality and costs compared to that of conventional practices.
Agrology partnered with O’Neill on the trial—which took place across 48 total acres planted to Cabernet Sauvignon Clone 15 and Petite Sirah in the Geneseo AVA of Paso Robles—to measure soil health, track soil measurements around CO2 sequestration and other factors, and collect data.
“O’Neill Vintners & Distillers has been practicing sustainable winegrowing as a pillar of O’Neill for 20 years. So to grow for O’Neill you got to be sustainable certified,” said Caine Thompson, head of sustainability at O’Neill. “Four years ago we came across a certification called regenerative organic. We heard about it through the Regenerative Organic Alliance and pilot project that was being run by our friends at Tablas Creek.” Regenerative Organic Certified was established in 2017 as a certification for food, fiber and personal care ingredients that represents the highest standard for organic agriculture in the world.
Regenerative organic viticulture employs the use of minimal soil disturbance, rotational grazing, compost and vegetative cover crop application and organic growing and pest management practices instead of more basic, conventional approaches like using RoundUp for weed control.
Thompson, who’s personally been farming with regenerative organic practices for nearly 20 years in New Zealand, pitched the idea for a regenerative trial to founder Jeff O’Neill and they decided to conduct a trial on a third of their estate.
Trial Set up
Forty-three acres were converted to regenerative organic while 5 acres (48 trial acres in total) were set aside to serve as the conventional control. For the regenerative program, a clemens undervine weeder was used to manage pesky weeds. Mealybugs were taken care of using bio-control methods (a mealybug predator was used along with mating disruption) while sulfur, pure crop oil, was used as a fungicide. To add nutrition, compost, biodynamic preps CPP, 500, and 501 were used along with comfrey, chamomile, nettle and organic products like zinc and oroboost.
Focused on a seasonal approach, in the spring, they mowed, applied barrel compound three times in addition to biodynamic preparation 500, used drone tech to conduct two drops of a mealybug destroyer predator, planted cover crops (annuals and perennials were planted to add more plant diversity and encourage beneficial insects into the vineyard) and conducted under vine weed control. Pheromone traps for the mating disruption of mealybugs were also used.
The conventionally-farmed 5-acre plot was given RoundUp, Rely, and Shark to control weeds. Pesticides like Wrangler were used and sulfur, Champ, Rally, Quintec and Tebustar were used as fungicides. For added nutrition, zinc, calcium and phosphate were added.
Back at the regenerative plot, during the summer months, teams did shoot thinning and green thinning as well as several compost teas and biodynamic preparations (BD) including: BD 501, silica X3; BD 508, horsetail; BD 507, valerian; nettle and comfrey tea and egg shells and chamomile. In the fall, after harvest, a barrel compound was applied three times and sheep were left to graze.
The Results
Before diving into the results of the trial, Thompson showed several side-by-side comparison photos of the conventional control vineyard and the regenerative organic vineyard in pre-harvest 2021, in summer 2022, and in pre-harvest 2022. In the photos you can see a progression where the regenerative organic vineyard is developing a thicker canopy with leaves that are darker and more turgid.
“In 2021 with that larger canopy, we actually had a slight yield increase… and that's not because there was more fruit on the vine. There was a canopy that was helping provide more shade so there was less shrivel and dimpling of the grapes in the regenerative comparatively to the control, so we had more intact fruit which was really interesting to see,” Thompson explained.
The 2021 yield increase was 14%, though the yield increase the following year, a dry year, was just 3%. Thompson said yield amounts bounced around a bit as in 2023 the regenerative vineyard actually saw a small, 9% decrease in yield.
In the regenerative organic vineyard there was also an increase in yeast assimilable nitrogen, YAN—2022 saw a 13% increase in YAN and 2023 saw a 17% increase in YAN. There was also better plant respiration with regenerative versus the controlled basic farmed plot and a 13% improvement in water holding capacity over the 2023.
Thompson and Charlie Dubbe, head of regenerative partnerships at Agrology, noted there was also better pore space, increased soil biological matter and better nutrient cycling.
Dubbe explained that when you create a more active soil microbiome it can enable the plant to better defend itself from pests and diseases because it allows increased production of plant metabolites.
“There's lots and lots of research that shows how a stronger healthier soil microbiome, allows plants to have an increased production of these compounds that are called secondary plant metabolites. Secondary plant metabolites are phytonutrients,” Dubbe said. They are chemicals that the plants use to defend themselves from both biotic and abiotic stresses, things like droughts or heat waves.
“What's really interesting is these are also the compounds that give wine its unique flavor and its unique profile. So these are compounds like tannins and all of the phenolic compounds and you know the list goes on and on, all the flavonoids, all the terpenes, all of these things. So, not only do you have less pest pressure and less damage from pests, but you're also in the end creating a higher quality wine.”
The presenters noted that when it comes to temperature, they saw cooler temperatures in the regenerative canopy because it was covered and armored by the desiccated and dry cover reducing the heat coming up and refracting from the soil.
Dubbe pointed out there was a 7.8% decrease in average daily high temperature during the critical harvest period in the regenerative block. On Oct. 6 the regenerative block topped out at 98 degrees while the control block reached 106 degrees.
For Dubbe, an exciting key takeaway when looking at these statistics is that landscape level cooling is possible through a shift in vineyard practices. He said we can cool the nano-climates around vines, as well as cool local watersheds and bioregions by keeping the soil covered with living cover crops and giving a boost to the microbial function of soils. This can lead to local climate repair and higher quality wines.
More living plants also equals more carbon sequestration and so the regenerative vineyard with the cover crops absorbed 192% more CO2 than the conventional vineyard.
Additionally, from August 2023 through August 2024, Agrology’s monitoring revealed that there was a 9.1% increase in microbial biomass carbon in the regenerative block, while there was a 2.8% decrease in microbial biomass carbon in the control block.
According to Agrology soil samples, there was an additional 12.23 tonnes of carbon per acre in the regenerative block versus the control block.
In terms of cost benefit analysis of regenerative farming, Thompson noted that they were looking at a 10% increase in the cost of farming when first starting the trial in 2021.
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“But because we had that yield increase in 2021, it actually translated to a 3% decrease per ton of regenerative organic fruit” in farming, “based on our farming costs and yield to the winery,” Thompson said.
Next Steps
Since the three-year trial was successful they expanded it from 43 acres to 130 acres of estate vineyards in 2021, and they plan to continue the trial. “And all company vineyards, 800 acres-plus, have conversion plans into regenerative as well,” Thompson said.
O’Neill received organic certification in January, 2024, and in August they completed an ROC audit and have a pending ROC certification.