Under Control - 2019 - 10

isn't much practical application of CEA
strawberry production in the U.S. "
He says one of the major reasons is the
limited availability of cultivars for CEA
growers. The breeding of strawberries
has been primarily for field production.
" The greenhouse strawberry market
is very small when compared to
field production. I expect there are
some growers producing greenhouse
strawberries who are using cultivars
that have been bred in Japan and the
Netherlands. Other growers are using
field-bred cultivars and adapting those
to the greenhouse environment. There
are breeding efforts occurring, but I
am unaware of any U.S.-bred cultivars
for greenhouse production that have
been released. "
One of the most affordable ways
for CEA growers to start producing
greenhouse strawberries is to use
off-patent, field-bred cultivars from
the University of California-Davis or
University of Florida breeding programs.
As part of the Greenhouse Lighting
and Systems Engineering (www.glase.
org) consortium, Allred has been
studying which field-bred cultivars are
best suited for CEA production.
" I started my research with seven
cultivars and very quickly narrowed it
down to two everbearing cultivars that
worked best for CEA production, " he
says. " 'Albion' and 'Cabrillo' are from the
UC-Davis breeding program. "
GREENHOUSE PRODUCTION TRIALS
Allred has been performing
greenhouse trials with 'Cabrillo' and
'Albion' for about a year. The strawberry
plants are being grown in 11-liter
buckets filled with a peat:perlite:coir
substrate mix. Each bucket contains
three plants, which are spaced at one
plant per square foot. Plants are watered
using drip irrigation and fed with a
custom-blended fertilizer, which is a
modified Yamazaki formula.
" We trialed production for a fivemonth
period from Jan. 1 to May 31, " he
elaborates. " There were three different
light treatments. Ambient light was the
control. The daily light integral (DLI)
was as low as 1-2 moles per square
meter per day.
10
The sweetness of the strawberries (Brix value) was highest for both 'Albion' (9.4°Bx) and
'Cabrillo' (7.3°Bx) plants grown under high pressure sodium (HPS) lamps.
" Supplemental light was provided by
either LED or high pressure sodium
(HPS) lamps. We achieved 98% light
uniformity over the crop canopy. The
DLI was set at 15 moles per square
meter per day, which is on the low end
for strawberries. We weren't looking
at the effect on total yields. We were
looking at the differences between the
light treatments. Greenhouse strawberry
growers would want to increase the
light intensity. For most strawberry
UNDER CONTROL: TIPS FOR CONTROLLED ENVIRONMENT GROWING * 2019
cultivars the recommended DLI is 20-25
moles. More light almost always means
higher yields for most crops. This is
something that needs further study for
strawberries. "
IMPACT OF LIGHT
Throughout the five-month trial,
the plants were maintained as much
as possible at three crowns per plant.
Within that requirement, under the
ambient light treatment, there was
Strawberry plants grown under ambient light levels never developed as many crowns as
plants that received supplemental light treatments. The vegetative growth of the ambient
light plants was also much slower.

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Under Control - 2019

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