hi and welcome to the micro YouTube channel my name is Shane and I'm the
founder of Migro today I'd like to help answer the question how much light do my
plants need when we're talking about lighting for plants we need to be
talking about the unit of measurement PAR not lumens or Lux which are units
of measurement of how we perceive light in terms of brightness PAR or
photosynthetically active radiation is a measurement of the useful light for
plants and we measure PAR of our photosynthetically active radiation
using a quantum sensor in this case have a Apogee SQ 500 which is a very accurate
quantum sensor and we're going to use this to measure power across the grow
area when we measure power across the grow area we don't just measure the
light in the center so you can see here the sensor is positioned directly
underneath the light and we're getting a an output here on our visual display in
hundreds of power of 250 and you can see as I move the sensor over the power
level here reduces to only 60 power at the side of the Grove area so when we're
assessing a grow area we measure the power level right across our grow area
so we divided it up into a grid we're going to measure in each of the squares
on the grid in order to assess how much light is going to be reaching our plants
we're going to put plants into each of these grow bays we have three lined up
and we have the grow lights on a different height by hanging the grow
lights at different heights we're going to achieve different power levels in
each of the different grow bays where the light is on lowest it's going to be
the highest power level but also it's going to be quite concentrated in the
center and we when we have the light positioned higher from our grow area
we're going to have a better spread of light but the
lament of power reaching the NGO area is going to be less because it's lost it's
been bounced off the side and it's illuminating the side walls and not
reaching the plant area so the height that we're measuring at that we have
this grid is positioned about 15 centimeters or 6 inches above the top
number part but this is just to give us a common claim and our measurement
surface which will represent the plant canopy when we put the plants into the
pots and do our comparison grow so first thing we're going to do is we're going
to measure the power levels across the grid in each of the grow areas and we're
going to look at those levels before we put the plants in under our grow test so
let's measure the power levels in each of these areas and then look at the
results so the quantum sensor is being positioned in each square in the grid
and the measurement of photosynthetic photon flux density is being taken in
each square this is the amount of paradise that's impacting that
particular area when we take the overall stimulated plant canopy we can then
overlay the individual measurements in each square on the grid and from these
measurements we can produce a par map which shows the gradient of prior
intensity across the grow area and we're also able to calculate the total level
of par for each glow area so we'll show each of the parallels now side by side
the lowest one 25 centimetres has an average power of 634 but a very high
maximum at 2130 which is a significant hotspot the middle hanging height 45
centimeters the average power is 10% reduced at 572 but a much better
max power at a thousand 60 at the higher hanging height the average prior is very
significantly reduced but it's a much more even coverage with juste hotspots
really the optimum hanging height here is the center one because we've achieved
a trade-off between having the maximum amount of power for the growing area and
having a high level in the center but not such a high level that it's going to
cause damage to the plants so we're expecting to get the best productivity
and grow the healthiest growth in the center Bay so here we have each of the
grow Bay's planted in each bay there is a tomato plant and the rear and bedding
plants to the front the soil pot sizes water regime temperature environment etc
all the same for each one the only difference being the hanging height so
the tomato plants their totem variety they've all got a similar amount of
early fruit on them on the front we have adding plants which should provide very
quick route and should show us some flowering characteristics and some
stretching under low light and good dense growth under high levels of light
so let's get these guys going under the time left to go we're going to run it
for four weeks and see what comes out on the other end
so you've seen in the time-lapse go over the four-week period there's quite a lot
of growth in both the tomato plants and the bedding plants we look where the
light level was least I the light was hung at the highest level there's quite
a bit of stretching here has occurred on the tomato plants of reaching for the
light so not enough light for that for the tomato plant and also on the bedding
plant huge amount of stretching it's reaching out way outside the part of
looking for light in the center one the light level for the tomato plant was
probably after them and that it gave very good growth nice healthy growth
whereas the bedding plant was still a bit further from the light and a bit too
far and stretched quite considerably on
the lowest level height level to the light there was way too much light for
the tomato plant so it has burnt and been damaged by too much light intensity
where it's got within the six inches of the bulb however the bedding plant has
done very well and it's very bushy and dense growth with little stretching and
lots of flowers so now we can have a look at this tomato plants and see how
they did in the grow test on the left is the plant that was under the light at
the high level so got the least amount of light and you can see the stretching
I think it's evident right here you can see the the tall distances between the
nodes on the growth and it's a fairly like Rose on the top the yield itself is
minimal three ripe and a three unripe coming up
behind us and very little else
you can see the middle which was that probably the optimum height the middle
level height and that's got good dense growth very healthy no sign of any
damage on top and an excellent yield lots of tomatoes ripening and loads
coming on behind just showing how healthy the plant is and the last one
was our low level plant unfortunately it's got a little bit of
burning also stretched up behind the light but yield was good it just didn't
have the comparable amount of you tomatoes coming up behind so now we have
the results for the bedding plants you can see from the left-hand side was the
higher hanging height or the least amount of light and we can see over on
this side we had a lot of reach coming from the plant still pretty healthy
growth on top and but not as has many flowers many blooms as in the center one
which again was medium height had quite a lot of stretch over the edge but also
very thick growth on top and on the right-hand side we had the bedding
plants that were closest to the light and you can see here that they grew up
nice and bushy nice and thick and lots and lots of flowers
so in short when you've got the light far away our low levels of light we get
stretch and when the light intensity is high either light is close to the plants
we get Bush dense growth so it's very interesting to see the outcome from the
experiment where we've had three different grow setups the only
difference being between each of them being the hanging height of the grow
light and the resultant power levels across the canopy of the growth
in the difference between each hang height was only ten centimeters or four
inches so you can see that the sensitivity of hanging height is quite
high and you can have dramatically different outcomes in the health of your
growth and the yields from your growth depending on the accuracy and the
quality of your lighting setup so two little paralyse we've seen results in
stretching and low levels of productivity to high levels of par and
low-hanging height results in in high intensity of power hotspots in the
center which will damage your plant and the adjustments to find that optimum
level is very fine within as I said 10 centimeters you can vary from a good
outcome to a bad outcome the setup we had initially was done using our quantum
sensor or Apogee esq 500 this really is the best way to understand what the best
hanging light is and to manage the trade off between hanging low and getting the
most par and hanging high enough so that the hotspots are reduced and the part is
spread as evenly as possible across your area so I hope this helps if you have
any questions please let us know and please subscribe
take care