June 2020 - 28

PRODUCTION
HOW MUCH COULD HEMP BENEFIT
FROM
Supplemental Light?
Research with grow lights could help growers improve propagation
and production of hemp, resulting in higher cannabinoid yields.
BY DAVID KUACK
W
hile hemp may not be
the cash crop many
growers initially thought
it would be, there are growers
who are looking for ways to make
it a profitable one. Numerous
universities across the country
are looking to provide growers
with production and marketing
assistance. Based on the interest
of growers and university
researchers, hemp still holds a lot
of potential for both controlled
environment and field growers.
Cornell University horticulture
professor Neil Mattson, who is
a member of the Cornell Hemp
Research Team, is conducting a
variety of studies including the
use of greenhouse supplemental
lighting for use on controlled
environment crops.
" Initially controlled environment
growers were thinking of using
greenhouses for propagation
of young hemp transplants that
would then be transplanted
into the field, " Mattson says.
" However, there are a couple of
commercial hydroponic lettuce
growers we are working with
who are doing quite a bit of
greenhouse hemp production.
In the same way that we are
28 JUNE 2020 GPNMAG.COM
interested in controlling light
and carbon dioxide for vegetable
crops, these growers are
interested in the impact light
and carbon dioxide can have on
hemp production.
" In my mind, the economics of
greenhouse hemp production for
CBD extraction remains uncertain.
We have heard of growers
producing higher value products
such as smokable CBD hemp,
or doing their own extraction/
value-added. Currently New York
State's hemp program doesn't
allow smokable hemp products.
However, controlled environment
growers in other states could sell
the flowers where smokable hemp
products are permitted. "
IMPACT OF SUPPLEMENTAL
LIGHT ON HEMP
Mattson is working with
graduate student Jack Wellhofer
to determine the effects of blue
light on hemp plant physiology
and the overall flower/CBD yield.
" This research is not being
conducted to address medical
marijuana, " Mattson explains.
" We are looking at the effect
blue light has on CBD and THC
levels. This research aims to help
growers who will look for lighting
techniques that can enrich the
CBD content while not surpassing
the legal THC threshold of 0.3%. "
The lighting research was
conducted using the hemp strain
TJ's CBD, which, according to TJ's
Gardens, tests from 13 to 18%
CBD. Plants were grown under
eight different light treatments,
including high pressure sodium,
metal halide and LED lights. Six
different LED treatments were
trialed including a white broad
spectrum LED, four treatments
consisting of different ratios
of red and blue light and one
treatment where plants were
grown under HPS lights and then
finished under high blue light.
" We are trying to test how
light would affect the stature
or the height of the plants as
well as yield, " Mattson says.
" Producing more compact plants
can be desirable. In some cases,
if plants grow too tall they
can become unmanageable,
especially in shorter greenhouses.
For smokable flowers or buds,
growers want tight or more
compact inflorescences instead
of loose, longer inflorescences.
" At the same time we want to
look at the actual yield, which
would be the weight of the flowers
after air drying multiplied by the
CBD concentration. In lettuce
production, higher blue light can
produce more compact heads of
lettuce, resulting in a 30% lower
fresh weight or harvestable yield.
We want to determine the effect
of these different ratios of red
and blue light on hemp yields. "
A related objective of this
lighting research is to determine
if the ratio of blue light affects
the actual CBD concentration.
" From the medical marijuana
world, there is anecdotal
evidence that higher blue light
produces higher THC content, "
Mattson shares. " In our case, we
need for the THC level to be less
than 0.3%. We want to see if blue
light affects CBD and THC and
if it affects these cannabinoids
in the same way. Does blue light
promote both CBD and THC or
does it preferentially promote
one of these compounds?
He says they can only conduct
research with hemp crops that
fall under federal guidelines.
But those implications could
affect growers producing
medical marijuana.
" We are looking at the effect blue
light has on CBD and THC to help
growers who will look for lighting
techniques that can enrich the CBD
content while not surpassing the
THC threshold. "
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June 2020

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