hello and welcome to the Migro YouTube channel today we're going to look at the
question what is the best spectrum for a grow light given all the different
technologies available be it the red blue LEDs high pressure sodium
full-spectrum LED and then the very confusing wide range of spectrum that
could be selected from each of those technologies and then on top of that you
have the providers of all these different spectrum telling you but
theirs is the best and for various different reasons and their spectrum has
some some properties which will give you a much better yield and another spectrum
and all the while it's very confusing because you you can't really compare
these things directly there doesn't seem to be any overview as to what the
spectrum really are made up of and what are the difference in our trade-offs and
between one and the other so we'll try and describe here and explain first of
all what in these different grow light spectrum what makes them different and
then what carat growth characteristics you can expect from plant your plants
who are grown under these different grow light spectrum we're not going to use
our own opinion in generating this information and providing it here we're
going to use a comprehensive recent study the effects of different grow
light spectrum on plants and it was done by scientists and Utah State University
just last year and we are going to show you going to extract the critical
information from this study and share it with you and hopefully as
straightforward and simple away as possible to understand so in this study
they used eight different grow light spectrum and you're just going to show
them here what their makeup is in blue green and red which are the Constituent
colors of our life you can see that they used three fairly extreme examples which
are almost pure blue green and red they're not generally
used or widely available is a light source but they've used them here for
demonstration purposes for this experiment and so we're gonna see what
the the extremes were producing in plant growth the five spectrum in the middle
however are are widely available and the the most commonly used grower light
spectrum for grow lights and it starts off with the on the left-hand side that
the warmer or lower color temperature and light mixes so you know typically
this would be down at the HBS spectrum where you be getting a warm orange light
and color temperature of around two to three thousand Kelvin and then as you go
along to the right you're getting an increase in the amount of blue in the
light spectrum and this turns the overall color from from being more
orangey to more blue and you get the cooler higher color temperature spectrum
when you have more blue mixed in with the the red and the green for each of
these spectrum then the in this experiment seven plant species were
tested they were tested under different levels of light but most importantly
they were tested for different growth characteristics and some of the growth
characteristics such as chlorophyll concentration P atoll and leaf area
we're not going to look at here because I'm not critical to us we're gonna look
at the ones which are most important as indoor growers which is the yield and
mass and the density of the growth which would be defined by the stem length or
the distance between nodes so we're looking at at dry mass yield first and
you can see that the red blue LED spectrum perform the highest it just
picked the other mixed spectrum by a small amount but
was definitely the highest so we have that and the mid temperature to the
three and a half thousand K spectrum very similar to the my go spectrum are
within 5% to each other and fairly clear at the top very interestingly the red
and the green and the blue and where it is not a large mixing of the spectrum
that they perform at the lower level so it does prove that you're better to have
a mixed spectrum rather than a pure spectrum in any particular of any
particular color next thing is you can see that the the green and the red are
very closely matched so they are as within 5% of photosynthetic efficiency
and the blue is significantly less than the red and the green but if you pick a
red blue green mix where you have blue in proportions of around 10 to 220
percent the productivity in terms of your I put whether you have green or red
mixed with that it's going to be very similar so really we're just looking at
targeting 10 to 15 10 to 20% excuse me blue next thing we look at is the stem
lend and it can be seen that the from the graph that the cool blue color
produced the shorter stem lent and we've set that at 100% very interestingly the
pure blue actually generated longer stem length so you know it does it does
demonstrate again that you're better off to mix your spectrum whichever
characteristic you're going for so after that you've got a range of
difference in terms of the stanlon stem length from the optimum but you can see
again that you are within 10% of that optimum by choosing either the red blue
or the mid color temperature so around three to four thousand k color
temperature you will get very close to the optimum in terms of stem lanta
combining the two characteristics together then which was yield and stem
blend your best to go for mixed spectrum between ten and 20 percent blue and it
doesn't particularly matter whether you mix that blue with red or with a mixture
of red or green they're going to be very similarly efficient from the study then
we can see that in terms of photosynthetic efficiency you've quite a
wide choice in terms of picking grow light spectrum the next but most
important aspect is looking at the system that you choose so we have taken
the measurements from lots of different bro light testing and also data sheets
from manufacturers websites and we have drawn up a table and this table is in
system efficiency which is the amount of power output amount of useful light
output for plants divided by the power consumed this is shown to you in units
of ppfd per watt starting off with LED red blue grow lights they have a range
of about 0.9 ppfd per watt up to about 1.5 that is the highest system
efficiency that we've tested and the highest that we can find
from any of the manufacturers data sheets or specifications looking next at
hid on the left hand side in the middle of the spectrum range you would have HPS
and ceramic metal halide those systems have peaked now really with an optimized
set up at about 1.4 micromoles per watt and could be as low as one might come
out for washing in a low-end setup when you go in to use the blue Domino bulbs
such as metal halide that system efficiency drops to a maximum of 1.3 or
so the most efficient technology widely available today is carp technology where
people are using and phosphor coated leds to produce a full spectrum white
light and the system efficiency of using the high efficiency drivers the Cobb
LEDs and glass lenses enables you to get very high efficiency of delivery of
light to your grow I've obeyed to micromoles per watt so when choosing
your grow light two aspects to consider in terms of the efficiency of the system
first is photosynthetic efficiency and second is your system electrical
efficiency hopefully we'll be showing you some information here that will help
you to to make the right choice for yourself for your grow and if you have
any issues please let us know in the comments below please check out the blog
for this video on the website also and look forward to your comments good bye
and take care