The Crush.March2022 - 2

FEATURE STORY CONT.
Winegrapes use low levels of N fertilizer compared with other
crops, but some practices can reduce N2O emissions further.
Many winegrape vineyards already use cover crops.
Marcus listed other considerations for vineyards. Tillage
practices vary widely and change with seasonal and climatic
conditions. Long-term no-till practices are not practical for
many sites, but every other row tillage can sequester C
compared with all-till practices while providing the grower
flexibility. This practice of " conservation tillage " is defined as
leaving 30 percent of ground cover. Current models do not
calculate the C sequestered in the vine and its roots. If vines
(when removed or pruned) are chipped instead of burned,
then this C could also be sustained, but additional work on
this issue is needed. Planting native plants and trees, such as
in hedgerows or in riparian corridors can sequester C even on
small vineyard sites.
SONOMA WINEGROWERS CLIMATE PILOT PROGRAM
Three Sonoma County vineyard managers provided
information on specific farm properties managed and
measured under the Sonoma County Winegrowers (SCW)
" Climate Friendly Farming " program and involved in the
CAC pilot program started in 2020 with 17 SCW member
vineyards. To date, modeling of different practices and their
impacts on C sequestration and emissions at each site have
provided comparisons for decision making.
Tyler Klick of Redwood Empire Vineyard Management
focused on Sei Querce Vineyards, a nearly 600 acre property
with 60 acres of premium vineyards that includes significant
acreage in natural open space with creeks, canyons and
native oak and conifer trees. Vineyard acreage is already
certified organic, and organic N and compost are used.
Cover crops are planted with grasses and legumes.
One vineyard block is dry farmed and the hope is to dry farm
more acreage as appropriate. Tillage has been reduced from
full till to no-till in some sites, and conservation tillage is used
in other sites. Klick said the property has eight different soil
types. " The proportion of clay, sand, silt and loam in each
vineyard site has different effects on C sequestration and
GHG emissions, " he said.
He believes conservation tillage would be better to use in
drought years, and no-till would be more appropriate in
normal water years. He advised, " We all need to be ready to
change our farming practices as the climate changes. "
Alejandra Alvarez-Gerardo of Treasury Wine Estates (TWE)
focused on the company's Grace Benoist Ranch in Carneros
that produces pinot noir and chardonnay for TWE's Etude
brand. The ranch is already certified under the Fish
Friendly Farming, Napa Green and California Sustainable
Winegrowing programs.
She said clay soils at the site sequester C, but rocky soils
not so much. Modeling shows no tillage will increase C
sequestration across all soil types, but this could be difficult
due to water conservation and vine needs. Conservation
tillage of every other row is currently used. Reducing the use
of mineral N fertilizer could increase C sequestration, but
substituting with compost could be more expensive and a
cost comparison is needed. Sheep are used to mow cover
crops and for weed control.
" Maintaining natural riparian areas and wooded areas allows
more C sequestration, and we plan to plant a hedgerow
and possibly additional native plantings to increase C
sequestration, " she said. TWE plans to further reduce its
carbon footprint by converting from diesel tractors to electric
tractors and electric vehicles throughout its operations, and
has a goal of using 100 percent renewable electricity by
2024.
Brad Petersen of Silver Oak Cellars discussed a 115-acre
property in Alexander Valley with 70 planted acres of
cabernet sauvignon on three main soil types and 20 acres of
adjacent natural area. The COMET-Farm modeling of current
practices shows that the proportion of sand, silt, loam and
clay in each soil type has a large effect on C sequestration
and GHG emissions. Gravelly loam soil with no-till can
sequester the most C. The property has used conservation
tillage since 2018 with grass and legume cover crops.
Although no-till will slightly increase C sequestration,
Petersen said, " No-till has a detrimental effect on vine
growth and fruit quality in some parts of the vineyard. " He
added, " Ultimately, we have to produce a high quality crop
for our ultra-premium wines, so that takes precedence. But
we are committed to sustainable practices. " The program
shows that planting hedgerows and native riparian trees
and oaks will increase C sequestration and this could be an
appropriate practice to implement. Transition from mineral N
fertilizer to compost applications may significantly increase
C sequestration, but Petersen said more analysis is needed
to determine the actual C footprint as the model does not
account for fuel use to transport and spread compost. A
comparison of differences in material and labor costs is also
needed.
Page 2 | March 2022

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