MJBizMagazine September 2021 Lighting Buyers Guide - 8

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But that fostered the myth that
cannabis doesn't need full-spectrum
light, Gerard said, and led to
disappointingly low harvests as
reported by indoor growers who
switched to red and blue lights from
their tried-and-true HID system.
But LED technology has advanced
since then, Gerard said, and broadspectrum
LEDs are much more
energy-efficient. However, focusing
on light quantity and ignoring light
quality (spectrum) misses the big
picture.
" You can't take a 10-watt light and
have it grow the same as a 1000watt
light. It's not possible, " Gerard
said. " But if your plant is unhealthy,
it won't capitalize on the energy it's
receiving. Spectrum plays into health
and plant shape. "
GREENHOUSE VERSUS
INDOOR CONTROLLEDENVIRONMENT
GROWS
Indoor growers must keep the lights
on a lot longer than greenhouse
producers, but it's more complicated
than just providing additional
light, said Erico Mattos, executive
director of the Greenhouse Lighting
and Systems Engineering (GLASE)
consortium.
In an indoor grow, spectrum becomes
critical because growers can't count
on natural sunlight to supplement
spectrum provided by indoor lighting,
Mattos said.
" If you have a bad spectrum in an
indoor facility, you'll have a bad crop, "
Mattos said.
Conversely, greenhouses do benefit
from supplemental lighting, which
may influence a decision in favor of
cheaper HPS lights rather than LEDs,
or less expensive but more energyefficient
LEDs in narrower spectrums,
Mattos said.
Studying the Benefits of
Supplemental Lighting
on CBD Hemp
Preliminary studies of different
light treatments found slightly
higher yields for greenhouse hemp
grown under white LED lights.
The study, conducted by the
Cornell University Hemp Research
Team in the winter of 2020,
compared hemp plants grown
under eight different light
treatments including high-pressure
sodium (HPS) lights, metal halide
and LED lights. There were six
LED treatments: a white broadspectrum
LED, four different red
and blue light ratios, and one
where plants were started under
HPS lights and finished under high
blue light.
CBD hemp bud harvested from Cornell
University/GLASE trial studying the
effects of different supplemental lighting
on yield and THC and CBD content in
CBD hemp production. Photo courtesy
of Neil Mattson, Cornell Univ.
According to Cornell horticulture professor Neil
Mattson, there was no statistical difference between
the light treatments on CBD or THC levels.
Mattson has also been studying light treatments
on hemp funded by the Greenhouse Lighting and
Systems Engineering (GLASE) consortium established
by Cornell University and Rensselaer Polytechnique
Institute.
He looked at three different autoflower strains grown
under four different daily light integral (DLI) levels
and found that two strains didn't increase in plant
dry weight above 20 moles of light. But one strain
did show an increase between 15 and 30 moles.
Future studies will look more at the effect of light
quality on CBD hemp yield and CBD content under
LEDs versus high-intensity discharge (HID) lighting
and compare the energy efficiency of the different
lighting sources.
" The research could show that the flower dry weights
and CBD yields are roughly the same for LEDs and
HID, but the electrical consumption for the LEDs could
be found to be 40 percent lower, " Mattson is quoted as
saying in an article on the GLASE website.
8
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MJBizMagazine September 2021 Lighting Buyers Guide

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