June 2020 - 16

IRRIGATION & WATER MANAGEMENT
Deeper dripping
Watering techniques come from Washington winegrapes
A deep root zone, or DRZ, subsurface drip irrigation system installed in Kiona Vineyards near Benton City, Washington. Photo: P.W. Jacoby
Conserving precious irrigation
By Stephen Kloosterman
Associate Editor
New techniques for irrigating
winegrapes with less water and for
higher quality are being developed by
Washington State University (WSU)
researchers.
Second only to California in
winegrapes' growing, Washington
cultivates roughly 60,000 acres. While
most of the state's 1,000 licensed wineries
are in or near the greater Seattle area,
the vast majority of vineyards are east of
the Cascade mountains and are heavily
reliant on irrigation. To find irrigation
techniques best suited to its unique
region, the wine industry in the state has
continued to fund research.
water and increasing grapes quality are
priorities for the state.
" Most of the vineyards are irrigated,
but that irrigation really gives the grower
complete control, " said Washington State
Wine Commission Research Program
Director Melissa Hansen.
Rootzone sub-irrigation
Research for watering replacement
vines was one new project among a
record $1.2 million of grants funded by
the state's wine industry for the fiscal year
that starts in July.
" I know the industry, they really
struggle with the replant situation where
you didn't replant the entire vineyard,
you just had replanted just a few trees or
vines, " Hansen said. " You always struggle
getting them established, because they're
competing against these fully-grown, big
root systems. "
The trial is looking at a new watering
technique developed by Pete W. Jacoby,
a professor and plant ecologist at WSU's
Pullman campus.
" He explored putting PVC tubes in
pipes down to the roots of the vine,
and then putting an irrigation spaghetti
tube in that PVC tube, so you're actually
putting water right to the root zone, "
Hansen said. " And he calls it, 'direct
rootzone sub-irrigation.' "
Jacoby said he's been perfecting the
system for several years. He said some
previous attempts at sub-irrigation had
failed because either the lines would clog
up, or the softer plastic would be chewed
by the local rodents (Belding's ground
squirrels, aka sage rats). The PVC pipes
though, protect the irrigation tubing.
The first-year study had involved basic
proof of concept - seeing how vines
with the system faired at 60%, 30% and
even 15% of the water typically used in
vineyards for surface drip irrigations.
Trials the first year showed it was possible
to get 70% of the yield of grapes using
only 15% of the water.
" Now, those vines looked a little sparse
in the canopy and the grapes were small,
yet they suggested that they might have
higher quality, " he said. They could get
90% of the yield at the highest treatment
using 60% of the water.
In 2016 and 2017, trials showed how
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June 2020

Table of Contents for the Digital Edition of June 2020