Biochar is a form of charcoal that is being tested as a soil amendment in several vineyards throughout Napa County as growers look to improve soil health, increase carbon capture and reduce nutrient inputs.
The use of biochar has the potential to provide the same or better vine growth with less fertilizer and nutrient inputs, and with less irrigation water, and that is the goal. It can also provide longer-term carbon benefits…the life in the soil is what it’s all about for us.
Among those exploring the use of biochar are Cakebread Cellars, Spring Mountain Vineyard and the Napa Resource Conservation District (RCD), which manages an experimental vineyard in Carneros. In Sonoma County, the Bedrock Wine Co.is adding the material to key vineyard properties. Elsewhere in California, larger-scale experiments are being conducted by Monterey Pacific vineyard management company and Bonterra Vineyards, with trials on both newly planted and existing vineyards.
Water conservation can be a long-term game but nitrogen is very immediate; it’s easily lost and critically important. Charcoal is a filter - it has a high surface area and adsorptive surface, binding nutrients in a way that is mostly plant available yet resistant to loss through volatilization or leaching.
On one block at a Bedrock property in Geyserville, a sizeable portion of the topsoil was scraped off and the subsoil contained low organic matter. In 2017, the cover crop didn’t properly establish leading the Bedrock team to explore how biochar might help rehabilitate the site. They worked with Pacific Biochar to apply a compost and biochar mix this past fall and the results have been dramatic. Vineyard manager Jake Neustadt recently reported that waist-high barley and a thick mat of sub-clover have taken root at the site. Jake acknowledged that he sees a profound impact of adding biochar on depleted soils.
A one-time application could have an impact on the soil that lasts for 500 years.
The Napa RCD also worked with Pacific Biochar at their Huichica Creek vineyard to apply a blend prior to a new vineyard planting in 2016. RCD also applied a blend to an existing vineyard in fall 2017 establishing controls for comparison in both cases. Two years after planting, early results show that the area with biochar has a higher carbon concentration and more organic matter. The RCD has also quantified a higher aggregate stability - improving soil structure and resilience to erosion.
In most every case biochar and compost together are better than either alone. When biochar and compost cure for a month or more we see increased benefits. But even without curing, a biochar blend is still better than raw - increasing and extending the benefits of the compost, with almost immediate reductions in ammonia smell.
Despite promising results, two significant barriers exist preventing more county-wide experimentation with biochar: cost and availability. Josiah Hunt with Pacific Biochar recommends a blend of 10-20 percent by volume of biochar mixed with compost for existing vineyards and a 20-60 percent blend for new plantings. Biochar is approximately $90 per cubic yard or ~$400/ton and a common application rate for an existing vineyard is a half-ton per acre. Annually, a grower should budget for $200 per acre, plus compost and hauling.
For existing vineyards, the total biochar application might be 3 to 4 tons spread over 6-8 years. For new plantings, a one-time application of 2 to 4 tons per acre has been effective in supporting more vigorous growth. Although the cost can be significant, the soil benefits can last for generations. Pacific Biochar works primarily through a distribution system and has worked with Napa Recycling and Waste Services, who will perform the compost blend and product delivery. Cool Planet is another California biochar provider with a product called Cool Terra.
Donation for Data: Is your vineyard interested in near-term biochar and compost application? Pacific Biochar is rolling out a Donation for Data program in April, offering a free truckload of their new premium biochar every month for the remainder of the year to a select number of applicants that can offer field trial data in return. Their biochar is sourced from California forestry residues, primarily from designated high fire hazard areas, contributing to productive utilization of dead standing wood and tree trimmings. For more information on the Donation for Data program, contact Josiah Hunt.
Biochar and compost can provide benefits if you have soil nutrient issues or low organic matter. Biochar can increase nutrient availability, soil organic carbon and water availability or water holding capacity, depending on the type of soil.