At Robert Hall Winery on Paso Robles’ east side, a remarkable three-year study is comparing yields, costs, wine quality and more in a conventionally farmed vineyard and a regenerative organic one (supplemented with biodynamic herbal and mineral sprays and compost). The results show a dramatic difference in water retention, soil respiration, soil carbon, wine quality and yields.
The regenerative organic certification (ROC) requires organic certification enhanced with additional practices, including no till, animal integration and keeping the ground covered. The standards were created and are enforced by the Regenerative Organic Alliance (ROA).
Usually, winery trials like this take place under cover of darkness and are typically aided only by subjective, qualitative assessments. Often, growers will try out organic farming on a block or two (and the same for biodynamics) and decide whether to implement these farming techniques. After several years of building their confidence through various vintages, they may decide to become certified organic.
Not so at Robert Hall, which has jumped into an impressive research study that is finding startling new results and is open to the public and peers thanks to an initiative proposed by General Manager Caine Thompson. The winery is also on the brink of ROA certification, having met all the requirements and awaiting the final paperwork.
Thompson praised the ROA certification not only for its faming standards but for the human social fairness practices it encourages. “We’ve got a really transparent feedback loop with monthly meetings with the vineyard team and myself and the winemaking team,” he said. “We’ve noticed more engagement, and turnover has gone down. The quality of work has gone way up.”
When Thompson came on board in 2020, he asked Jeff O’Neill, CEO of O’Neill Vintners & Distillers, if he could conduct a side-by-side comparison and measurement of conventional versus regenerative organic (no till and more). Tablas Creek, certified both biodynamic and ROC, had previously worked with academics to study the impacts of tillage and grazing, which provided a helpful precedent. O’Neill gave the Robert Hall study the thumbs-up.
Thompson, a native of New Zealand, had personally been farming organically and biodynamically for 20 years in New Zealand at Pyramid Valley and Mission Estate Winery and had previously conducted research on converting to organic.
Begun in 2021, the Robert Hall study encompassed 48 acres in the vineyard surrounding the winery (in the Geneseo AVA). 43 acres were converted to regenerative organic. 5 acres were retained as the conventional control. The control includes the use of cover crops and compost which advantaged it with better practices than the average conventional vineyard (though cover crops are widely used). Both the control and regenerative organic vines are Cabernet Sauvignon (clone 15, originally from the Bordeaux region).
Thompson wanted to make sure he was measuring like with like and went the extra mile to make sure that was the case. “We had satellite images and soil maps to ensure we were setting up the trial with like for like literally side by side, the same soil type and the same clone,” he said.
Four years later, he and his team have a lot of data to look at and experiences to review.
Their ongoing study is finding regenerative organic practices have benefits that exceeded their expectations. “I was surprised at how quickly the differences showed up,” he said. “Even in year one, there were noticeable changes.”
On a vineyard tour in November, he pointed to a newly planted neighbor’s vineyard, where the soils were clearly pure hardpan.
“When we broke ground farming this way four years ago, you could barely get a spade into the ground,” he said. “Now, we’ve got a living, breathing soil.
“The soils are more open, more friable, and there’s just so much more life within the vineyard. When you walk into the vineyard now, it’s like this biodiversity nightclub of energy and insects and life all around you, and I think that’s translocating down through the roots, into the soil, and you’re getting that expression back up into the fruit and then into the resulting wine,” he said.
Regenerative organic farming is easier in addition to being more rewarding financially, he said.
“When you have that type of biodiversity within a vineyard, the diversity and the predators take care of a lot of the pests and disease. You’re building these polycultural systems; it’s not just a monoculture. You’ve got a whole bunch of different cover crops growing in there and different species. You get more diversity through predators in there, so the pest populations get brought into balance naturally,” he added.
“When we started the project, we were doing three to four biodiversity drops of pest predators to build up a baseline [predator] population. Now we’re only doing one or two. They’re basically maintenance drops now, and of course, there’s no insecticides being used, no herbicides being used, no synthetic fungicides.”
The team has the data to prove yields are up, water retention is up and wine quality is improving, he said. In 2021 and 2022, they collected all the data themselves.
Agrology Technology Adds Insights: Water Retention Up 13%
In 2023, the study began integrating state of the art carbon monitoring and other data-gathering technology from Agrology, measuring soil moisture, soil respiration, CO2 in the canopy, carbon concentrations in soil, and ground and canopy temperatures.
The team found the regenerative organic block increased water retention 13% in just one year compared to the conventional block. In a region that typically gets only 18 inches of rain per year, while the climate continues to warm, that is significant.
The regenerative organic vines also boosted microbial activity, Agrology found.
Regenerative Organic Mitigated Heat and Heat Spikes
This fall, Paso’s heat spikes shattered heat records for six days in a row, reaching a high of 107 degrees F and affecting soil temperatures.
The regenerative organic block were consistently lower in temperature than the conventional block, the data showed. Similar results applied in measuring the canopy temperature.
The team calculated there was “a 7.8% decrease in average daily high temperature during the critical harvest period in the regenerative block,” when grapes are typically in danger of ripening too quickly.
Carbon Sequestration Bolstered
In October 2023, the accumulated canopy absorption of CO2 was 26.79 PPM in the control block versus 1,397 PPM in the regenerative block, leading the study to conclude the regenerative block absorbed 192% more CO2 than the control. Organic carbon in the regenerative block was 1.51% vs 0.86% in the conventional block as of July 2024.
The regenerative block scored 7.8 on the Haney soil health score compared to 4.7 for the conventional block.
Yields and Costs
Yields were up three out of four years in the trial, while farming costs increased an average of 10% annually overall, Thompson said.
In the trial’s fourth year (the 2024 vintage) during another warm vintage, yield data showed a 15% increase in the regenerative organic vines.
The conventional control yielded 1.85 t/acre while the regenerative organic yielded 2.17 t/acre. The data highlights in three out of four years, the regenerative organic vineyard has produced a more resilient canopy that has helped protect the fruit, leading to improvements in yield.
Wine Quality Skyrocketed
Another major benefit was dramatically increased wine quality.
Thompson and winemaking partner Amanda Gortermade made wines the exact same way from both the conventional block and the regenerative organic block. After seeing dramatic improvement in wine quality, they upgraded cultural practices in specific areas within the regenerative organic vineyard, increasing shoot and crop thinning in the hopes of creating a $50 bottle wine. Mission accomplished.
“There’s more complexity in the wine compared to the conventional control,” Thompson said. “There’s freshness, there’s more vibrancy, there’s a different energy in the wines. We’ve got more of those classic Cabernet characters,” he said.
Sharing the Data (and the Wine)
An advocate for regenerative organic farming, Thompson is enthusiastic about sharing the trial’s data and findings with the world.
“The whole idea of the study was to be collaborative, to be open to industry,” he said. “We hold quarterly field days to share the results and the learnings and this whole journey toward regenerative organic.”
Visitors are welcome to taste the wines side by side from the trial during field days (open to all) to compare the differences for themselves.
Thompson’s scope in applying learnings from the study is wider than the vines at Robert Hall. He oversees sustainability for all O’Neill Vintners & Distillers properties (the seventh-largest winery in California) and sits on the boards of several international sustainability groups.
O’Neill’s vast holdings include 870 acres in Parlier, Calif. The company also contracts 200 growers with 15,000 acres of vines. All are now required to meet some kind of sustainability program requirements. In July, O’Neill purchased its first Washington winery, Wines of Substance. O’Neill’s luxury brand, Ram’s Gate in Sonoma, is in the process of becoming certified regenerative organic on 28 acres in the Carneros AVA.
Thompson’s study has reinforced his belief and experience that regenerative organic winegrape growing can be profitable for all.
“We now have a vineyard that’s alive, that’s diverse, and more resilient in the face of climate related issues and pests and disease,” he said.
“The vineyards are definitely becoming more resilient to climate change and some of the extremes that we’re seeing with temperature, with heat, and the pressure that’s put on canopies and fruit. Under the regenerative organic side, we’ve got a bigger, healthier canopy, resulting in more shade and protection. We’ve got darker, greener leaves that are working really efficiently, and they’re protecting the fruit. Those leaves obviously move with the sun, but they protect the fruit in these larger canopies, so the resulting fruit is intact. It’s not shriveled, it’s not dehydrated, and that’s leading to better wine quality,” Thompson added.
Robert Hall Winery offers consumer and trade vineyard tours to the control and regenerative organic blocks (side by side) and schedules field days that provide growers and others to learn in depth about the trial.
The full study can be seen online at shorturl.at/suO86.