Tony Chapman: Building The Donum Estate’s tailored regenerative system

For the last few years at Donum, Tony has been working on collecting data on how tilling choices alter soil health, vine performance, and taste profile of the wine itself. 

The estate began by trialing a three-acre block, split into three treatments: one acre of 100% no-till, one acre of minimal till, and one acre of conventional alternate-row tilling. To maintain continuity, all blocks shared identical rootstocks, clones, cover crops, and inputs. Despite harvesting the grapes at the same time and vinifying them under identical conditions, blind tastings showed that the wines differed in flavour profile. This confirmed to Tony that tillage methods were an influencing factor in wine taste and quality.

To explore these findings, Tony began a second, six-year trial on the opposite edge of the estate. This trial compared a minimally tilled block (spaded once a year) against a 100% no-till block. Partnering with Agrology, the team tracked carbon flux, soil respiration, vapor pressure deficit, canopy temperature, and soil humidity, alongside routine Haney soil analyses.

Following spading in the minimally tilled block, ground carbon peaked at nearly 10,000 ppm, a level too high for the vines to utilise, causing the excess carbon to escape into the atmosphere. The no-till block consistently remained under 900 ppm. At this level, the soil respires just enough carbon for the vines to photosynthesise efficiently, allowing them to pump that carbon back down into the soil via the liquid carbon pathway. 

These findings indicate a soil environment that has successfully transitioned from chemical dependence to a biology-driven system. In Tony’s words:

Donum’s location in Carneros, where heavy, shrink-swell clay soils are prone to compaction and anaerobic conditions, makes Tony’s findings even more compelling. Local farmers often claimed that no-till wasn’t possible in these soils, but this trial has proven otherwise.

When transitioning a vineyard or block to no-till, preparing your soils first will maximise its benefits!

When Tony first arrived at Donum, the vineyard soils were heavily compacted from decades of running a heavy disc at least three times a year. This practice created both surface compaction and a dense hardpan layer 12 to 24 inches below the surface.

To transition a compacted site successfully, Tony recommends these guidelines:

• Break compaction first.
  Run a deep tillage tool once through the rows to shatter the deep hardpan. It’s key that this tillage should be timed carefully however, as to prevent soil smearing or further structural damage.

• Introduce oxygen.
  Breaking up the hardpan reintroduces oxygen into the soil, encouraging fungi growth and healthier cover crop development. After preparing the soil and making the shift towards no-till, Tony has seen Donum’s soils shift from being bacteria-dominated to fungal-dominated!

• Think carefully about cover crops.
  This will be your ‘engine’ for going no-till, according to Tony. Read more on cover crops in the section below.

• Kick start soil biology with inoculants.
  Soil inoculants, like compost teas and microbial inoculants, will boost and restore biological activity that will maintain soil structure.

Across Donum’s five estate vineyards, cover crop design is guided by two principles: high biodiversity and continuous seasonal activity. Specific plant families are chosen for their functional traits, based on soil type. 

Due to Carneros’s heavy clay soils, the Donum team often opt to use grasses to add structure and send roots deep into the soil to support aeration and water drainage. Tony has found that oats crimp very well, making them a great fit for a no-till system. They also include legumes for nitrogen fixing.

Because it is impossible to predict exactly how a plant species will behave in a specific soil context, introducing new cover crops can pose ecological risks. Some varieties can become invasive or upset the natural balance of the vineyard. 

To avoid these risks, Tony advises:

1. Start small.
Always trial new seed mixes on a small scale first to assess plant behavior before committing to a vineyard-wide rollout.

2. Monitor long-term persistence.
The Donum team seeded vetch eight seasons ago, and the plant continues to return vigorously every year without reseeding. The estate also currently faces challenges with field marigold, an undervine crop that sprouts everywhere in spring. Because it lacks sugar content early in the season, grazing sheep don’t want to eat it, allowing it to out-compete young vines. 

3. Remember that every vineyard is a different story!
Different crop species can act invasively depending on context. Everything is vineyard-dependent, so starting small will not only ensure a natural, non-competitive balance between plant species and vines, but also help you learn which plants work better for your vineyard.

Donum makes its own compost and biological extracts entirely on-site. The composting program focuses heavily on supporting fungi, which serve as the primary decomposers of complex plant materials like lignin. 

The estate partners with local organic dairies in Sonoma County to source organic animal manure, which is combined with green manure to provide a balanced nitrogen source. To build a fungal-supportive environment, they incorporate carbon-rich, woody material. Raw wool is also mixed in, keeping the compost aerated.

When the compost piles require moisture, or when the vines need a biological boost, the team use home-brewed compost teas. 

Donum has two 500-gallon custom brewers, which can produce 1,000 gallons of compost tea within 24 hours. This tea acts as an inoculant, which has multiple uses: 

1. Directly through the vineyard irrigation lines
2. Applied as a foliar spray
3. Sprayed onto the soil surface
4. Used to water active compost piles
5. Used to charge biochar before application

Managing pests and disease in a certified organic, regenerative system requires a shift from an eradication mindset to an eco-system balance mindset. 

At Donum, Tony uses a dual-pronged approach to manage pests organically:

Tony uses the presence of native bird populations to defend against vineyard pests. On-site, there are healthy populations of kestrels, hawks, owls, western bluebirds, and swallows.

After assessing which species could be most beneficial to them on the vineyard, Tony found that mud-nesting swallows are very good at maintaining populations of leafhoppers, cane borer beetles, and caterpillars. This led Tony to develop a targeting approach to increase mud-nesting swallow populations on the vineyard; they are currently experimenting with building artificial eaves for the swallows to nest in. 

The trial eaves successfully stimulated local nesting activity, prompting the team to plant perennial native flora underneath the structures to further support the birds. If they continue to see positive results, these structures will become standard of all Donum’s future vineyard redevelopments.

Note: While beneficial birds are encouraged, grape-eating species are managed during ripening using bird netting to protect the fruit.

Rather than spraying on a schedule, Tony uses a proactive approach that combines spore tracking with biological rotations to preserve the native wine fermentations. This is his framework:

• Spore monitoring.
  By partnering with Root Applied Sciences and Scanit, the estate monitors ambient fungal spore loads to dictate exact spray intervals and choice of material.
• Shutting the sprayers down early.
  If spore counts show low levels of disease pressure, Tony shuts down the sprayers early in the season at around a 5-8 Brix reading. If an active powdery mildew infection is detected, spraying is extended up to a 15 Brix reading to protect the crop.
• No-sulfur use.
  Traditional late-season sulfur applications (post-bunch closure) are typically avoided at Donum. Residual late-season sulfur can drive native yeast fermentations into a reductive state in the cellar, compromising wine aroma and clean expression!
• Use biological rotations.
  To keep input costs manageable, early-season sprays utilise affordable oils and elemental sulfur. As the season progresses, the program rotates through commercial biologics (such as Regalia, Serenade, and AEA’s Pinion), making sure that at least two distinct biological modes of action are active on the canopy at any time. This is then supplemented with their home-brewed, fungal-dominant compost teas to build disease resistance.

Whether you’re trialling a new cover crop mix, adjusting your termination timing, or transitioning rows to no-till, understanding what’s working requires good observational records.

Sectormentor makes it straightforward to log vineyard observations, track soil health progress, and build a long-term picture of how your land is responding to regenerative practices. Over time, that data becomes one of your most valuable assets, helping you make better decisions according to your vineyard context.