ask the experts
Q
– Michael
Thanks for writing in. That is a good
question. Let’s first look to the sun
for some information. The sun is the
Earth’s grow light and produces more
than 100,000 lux, or roughly 10,000
lumens, per square foot. This can be
even higher when under direct sun.
Lumens are a measure of the amount
of light cast on one square meter.
Most styles of artificial lighting do not
provide anywhere close to that, but
more important than lumens, which
refers to the amount of visible light,
is the amount of usable light. Plants
see light differently than we do. They
utilize much more of the red and blue
spectrums of light, which the human
eye is not as sensitive to.
Plants use light during the process
of photosynthesis. For this reason,
it is important that your grow
lights produce light waves in the
wavelength ranges that are useful
for plants, primarily the 400-700
nanometer range. Most lights
cover all spectrums, but some are
manufactured to produce light in
certain spectrums more than others.
Let’s go back to lumens and how
much can be used. Illuminance is
the way most growers judge their
light. Most agree that ideal light
levels fall somewhere in the range
of 30,000-60,000 lux for vegetative
growth and between 50,000-80,000
lux for the flowering stage. Serious
plant problems surface at light levels
above these, not to mention heat.
CO2, which is also involved in
photosynthesis, is also essential for
plant growth, but there is a threshold
of how much your garden will use.
YK?
A
What are the maximum light and CO2 levels that can be applied to
a plant before destroying it? Please take into account that limiting
factors are all under control. Thanks!
Ambient levels of CO2 hover around
400-500 ppm. When you increase that
level to around 1,000-1,500 ppm, you
will see an increase in your yields and
your plants will be much healthier.
If the level is allowed to rise to 2,000
ppm or higher, you will begin to see
negative effects such as CO2 burn. It
is best not to allow your CO2 levels to
increase this high. Doing so not only
hurts your garden, but it wastes CO2
and money. As far as your choice of
products, I would suggest using an
all-natural form of CO2 production
versus a propane burner system or a
tank system. The burners create heat
and require the use of fossil fuels and
tanks are cumbersome and must be
refilled often.
You should supplement your garden
with CO2 during both the vegetative
stage, as well as the flowering stage. If
you encounter high temperatures, CO2
will help your plants tolerate the high
heat. In some instances, it may be what
saves your garden from disaster.
Glen Babcock
is the owner
of Garden City
Fungi and the
founder of ExHale
Homegrown
CO2. Glen has
been involved
in agriculture
his entire life. He graduated from the
University of Montana with a degree in
forestry and has been a mycologist for
more than 26 years. His research has been
published in scientific journals worldwide.
LUMENS
The lumen (lm) is a unit of luminous flux; a measure of the total quantity of
visible light emitted by a source. Lumens are related to lux in that one lux is
one lumen per square meter. The lumen is a measure of the total amount
of visible light emitted from a given source, dependent on spectrum. Watts
(W) is the measure of the amount of energy required to light a product,
whereas lumens measure the amount of light produced. The more lumens
in a light bulb, the brighter the light.
24
Maximum Yield USA | December 2016
– lumennow.org