Maximum Yield Australia/New Zealand May/June 2019 | Page 74

Fig. a
60”
height
15” 720 878 858 878 720
20” 460 616 614 616 460
25” 228 447 484 447 338
30” 263 334 370 334 263
PPFD readings for a moving grow light.
60”
height
15” 90 590 2815 590 90
20” 122 602 1472 602 122
25” 148 512 942 512 148
30” 166 419 638 419 166
35” 170 339 456 339 170
40” 163 280 353 280 163
45” 151 230 275 239 151
PPFD readings for a stationary grow light.
To understand this on another level, stationary grow lights
are always at a reduced strength because of the limitations
of stationary grow light rules. It’s a paradox of having a
beautifully strong, quality grow light that is forced to be
positioned up high so that it is safely diluted, so as not to
cause harm. Then, as a strategy to get some degree of grow
light strength back, a grower is forced to place their grow
lights in a tighter formation, resulting in more grow lights in
use. Beyond the logical conclusion that this is wrong for cost
and for practicality, it is also wrong for efficiency of electrical
usage. With light movers, the grow lights can be positioned
much closer and they can cover about 30 per cent more area
— and that’s per grow light. That’s with each light mover
consuming only about five to nine watts. In a time when
electrical savings and energy efficiency are as important
as yield numbers, moving grow lights is a way to have both
variables significantly improved.
The PPFD chart tells the story of an even canopy, along with
faster growth and yield increases due to the moving grow
light. A side story is the effect of the optimised moving grow
light that moves off-side slightly and then back intensely
overhead, again and again. This ongoing action reduces
shadow patterns and is how more of the leaves interact
with the grow light. It mimics how plants have evolved over
millions of years to best receive light. Plant receptors will
open more when the light is intense but intermittent. So, the
light mover’s effect on PPFD readouts is perhaps the most
important grow light variable to know. It’s a story of better
coverage and the effect goes even beyond the chart numbers.
But, grow lights have their own input and there are many
grow light numbers beyond PPFD to decipher.
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Maximum Yield
“This is how to best maximise PPFD with
stronger/better coverage while creating better
efficiency than with a stationary grow light.”
Breaking Down Grow Light Numbers
The following breaks down some of the most common grow
light numbers used, along with the ones to pay particular
attention to.
Lumens and LUX
Lumens are actually an eye measurement, so these are
numbers strictly from a human perspective. It revolves around
a photopic bell curve where humans are sensitive more in
the middle for green light and less sensitive on the ends for
blue and red light. LUX is simply a measurement of lumens in
feet as lumens/ft squared. Because lumens and LUX deal in
human terms for light, they are somewhat weak in the far ends
of the spectrum. Humans don’t need the far-end colours to see
well but plants absolutely use the reds/blues as the fuel for
photosynthesis. Because of this, we need those far-spectrum
numbers represented. Lumens and LUX don’t give us grow
light numbers at the plant’s perspective and because of this,
they are not really useful terms for grow light output.
Watts
Watts is a term used for an overview only and is not
used for accuracy. In other words, our general acquired
knowledge might be to know which wattage is ideal for
what we grow and at what stage.