Tablas Creek – Water Retention in the Soil

Tablas Creek – Water Retention in the Soil

EXECUTIVE SUMMARY

Wine grapes are grown mostly in Mediterranean climates where water availability is threatened by climate change. At our vineyard in Paso Robles, we have made a successful transition from irrigated to unirrigated plantings over the last two decades, and implemented several changes to improve our soil’s water-holding capacity. These have included Biodynamic and Regenerative Organic farming, a flock of sheep and a rotational grazing plan, the application of biochar, cover cropping, and using a keyline plow to encourage water absorption. Together, these show great promise for reducing water usage for vineyards in warm, dry climates.

SDG (SUSTAINABLE DEVELOPMENT GOALS)

6, 12, 13, 15

Paso Robles and all of California is perpetually water-threatened, with climate change exacerbating drought both through greater summer dehydration and through moving winter rainfall patterns north. In a 2022 survey of Paso Robles wineries, 90% of respondents listed “water availability” as a concern, the highest total of any region in America. The growing stress on shared groundwater supplies has accelerated our transition to dry (unirrigated) plantings, and the soil’s ability to hold water is critical for this transition to be successful.

PROJECT DESCRIPTION 

We attacked this in multiple ways, most notably by increasing the carbon content of our soil. These have included:

• A transition to Biodynamic and (more recently) Regenerative Organic farming
• The implementation of a flock of 200 sheep and a rotational grazing plan to get the flock through the entire vineyard multiple times each winter
• The application of biochar, first from purchased material and in the last two years from our own kiln and made from our own vine material and fallen trees from our woodlands
• Planting a cover crop mix before the winter rains begin to minimize erosion and build soil fertility
• Using a keyline plow to cut furrows perpendicular to the slope of the hillsides so that water flowing downhill stops flowing and settles

BENEFITS/ACHIEVMENTS

We now have nearly half our vineyard planted without any irrigation infrastructure. On the older, close-spaced blocks we apply about 40% of the irrigation that an average vineyard in our climate would use. We have been able to maintain yields between 2.5 and 3 tons per acre and the quality of our grapes and wine has never been better. The dry-farmed blocks thrived through the 2012-2016 drought, when we averaged just 15 inches of rain per year, and outperformed the irrigated blocks in those drier years.

LESSONS LEARNED

In a dry Mediterranean climate it’s possible to farm with minimal or no irrigation if you plant wide-spaced (350-600 vines per acre) and have soils that hold the rain you get.

NEXT STEPS

Investigate different approaches to tillage. There is conflicting evidence between the benefits of moving toward no-till farming and for early-summer creation of a surface “dust mulch” layer as a way of protecting moisture in deeper layers. It’s likely that there are benefits to both approaches but it remains to be seen which provides the greater benefits.

POTENTIAL FOR REPLICATION 

High. These involve a range of different approaches and could be used together or individually. Just because one piece isn’t feasible doesn’t mean that others wouldn’t work.

SOURCES OF INFORMATION/SUPPORT

For the transition to Regenerative Organic, the Regenerative Organic Alliance (http://regenorganic.org). For rotational grazing, the Savory Institute (https://savory.global/). For keyline plowing, Yeoman’s Plow (https://yeomansplow.com.au/).

ADDITIONAL COMMENTS

We document this work and provide ongoing updates, share our successes and challenges on the Tablas Creek blog (http://tablascreek.typepad.com).