OF June July 2021 e

UNIVERSITY OF CALIFORNIA
HEMP RESEARCH
TO ADDRESS HEMP RESEARCH TO ADDRESS WATER, N ISSUES IN 2021
By JEANNETTE E. WARNERT | Communications Specialist, UC ANR
Researchers found that hemp appears to be tough under deficit
irrigation, a method of conserving water by applying less than what
might be considered optimum for maintaining rapid growth (all photos
courtesy B. Hutmacher.)
UCCE and UC Davis research efforts
to understand the opportunities
and challenges for industrial
hemp production in California are
growing.
As a crop relatively new to California
growers and researchers, there is still
much to learn about variety choices,
how varieties and crop responses differ
across regions with different soils and
climates, best practices for nutrient
management, and pest and disease
issues.
valued for its fiber
and edible seeds;
however, in California,
producing
hemp primarily
for essential oils,
including medicinal
cannabidiol
(CBD), is thought
to offer the best
economic outlook.
U.S. and California
hemp acreage
surged in 2019, but
fell in 2020.
Hemp Water-Use
Study Expands
In a study coordinated
by Jeff Steiner
of Oregon State
University’s (OSU)
Global Hemp
Innovation Center,
drip irrigation trials
are underway
in California, Oregon
and Colorado.
Research was conducted in 2020 at the
UC West Side Research and Extension
Center in Five Points and at the UC
Davis campus in addition to three sites
in Oregon, with an additional site in
Colorado added in 2021. These studies
were set up to determine water use of
industrial hemp for CBD production
under irrigation regimes ranging from
about 40% to 100% of estimated crop
water requirements, with comparisons
of responses observed across the five
sites with different soils, climate and
other environmental conditions.
not require shortening day length to
flower.
Some of the irrigation treatments
impose moderate to more severe deficit
irrigation to help assess the crop responses
to water stress. Deficit irrigation
is a method of conserving water
by applying less than what might be
considered optimum for maintaining
rapid growth.
“This plant appears to be quite tough
under deficit irrigation,” said UCCE
Specialist Bob Hutmacher at the UC
WSREC.
“We need to learn more about benefits
and drawbacks to stressing the plants,”
Hutmacher said.
The auto-flower cultivars tested tend
to use less water than the photoperiod-sensitive
cultivars because they can
be grown in a shorter season. In the
San Joaquin Valley, auto-flower cultivars
in these studies were ready for
harvest in 75 to 90 days after seeding.
“Water use is very variety-specific”
Hutmacher said. “Auto-flower varieties
may have potential to be grown in the
spring and harvested by early summer,
or planted in late summer and harvested
before winter. With a short-season
crop, and with a decent water supply,
farmers could consider double-cropping
with such varieties, potentially
increasing profits.”
Yields were variable, but showed promise
for auto-flower varieties.
Industrial hemp field research efforts
began at the University in 2019 after
the previous year’s Farm Bill declared
the crop should no longer be considered
a controlled substance, but rather
an agricultural commodity. Hemp is
The study, funded by USDA and OSU,
includes photoperiod-sensitive cultivars,
where the flowering response is
triggered by shortening day lengths in
mid- to late summer in central California,
and auto-flower varieties that do
“In our studies, the highest-yielding
auto-flower cultivars have produced
80% to 90% of yields of the much
larger full-season, photoperiod-sensitive
plants, and some varieties may be
equal,” he said.
26 Organic Farmer June/July 2021