Study shows 14% increase in tomato yields with interlighting

"A study by a Dutch university has shown that placing about a third of a greenhouse’s LED grow lights among high wire tomato crops rather than suspending all of them above the vines can increase the yield, according to lighting company GE Current, which supplied the fixtures."

nice to see a study for interlighting.

Interesting. I wonder if this is because LEDs don't have the same light penetration has a HID or the sun.
I believe this is why pruning correctly when you're using an artificial light is so important, the light doesn't get to every leaf and the plant doesn't get to use them to their fullest ability. I suppose if interlighting helps with this and saves greenhouses time, that's a win.

Brings back memories of the suncloak system .now leds have close 200lm/w, instead of not sure 50lm/w ?

SpideyManDan said:

Interesting. I wonder if this is because LEDs don't have the same light penetration has a HID or the sun.
I believe this is why pruning correctly when you're using an artificial light is so important, the light doesn't get to every leaf and the plant doesn't get to use them to their fullest ability. I suppose if interlighting helps with this and saves greenhouses time, that's a win.

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how many penetrations is HPS????

SpideyManDan said:

Interesting. I wonder if this is because LEDs don't have the same light penetration has a HID or the sun.
I believe this is why pruning correctly when you're using an artificial light is so important, the light doesn't get to every leaf and the plant doesn't get to use them to their fullest ability. I suppose if interlighting helps with this and saves greenhouses time, that's a win.

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normally the more lightsources you use and the better spread they are dictates "penetration".
so leds are normally better in this regard.
probably leds are used as its convenient using them this way ?, they dont suffer the efficiency loss HID would have when taking a 400W and a 200W instead of a 600W or else.

MidnightSun72 said:

how many penetrations is HPS????

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Lols, There we go with the P word again.
I hate it with a vengeance, everybody throws it around as if it was a thing but nobody seems to know what it is.
Is it lightlevels in the intracannopy or is it how far down you can grow decent buds? Cause those two things are NOT the same. You can get buds low in the cannopy where you have seedling light levels, as long as youve done some pruning qnd as long as you have a good root stock and sufficient light at top cannopy.

efi2 said:

Brings back memories of the suncloak system .now leds have close 200lm/w, instead of not sure 50lm/w ?

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I remember those, Hybrid had some really good goes with them. I dont understand why we dont see more people just sticking some strips to the wall and side lighting their entire space. Say if you have a 2x2x6 closet and light from 1 foot and above from two sides: thats 5x2x2= 20 square feet of lit cannopy instead of a maximum of 4 if you only top light.

Funny I read the word penetration recently in a study and it's ok since by association anyone should, at least, be put into the right direction of thought. As there are just way too many different phenomenae described that add to that topic and "transmittance, reflectance" don't cut it.
There's fluorescence based on colour or energy of the photon, angle of incidence when a point source light like a HID under a spreader releases light in all kinds of angles, then Sieve & Detour effect that works better on a central pointy strong light emitter (it's usually adjusted to do away a bit of the sun's ferocious input) and color based high or low absorption. The LED's blue and red will be readily absorbed by chloroplasts in the upper part of the leaf.

One thing with LED sidelighting is the minimum distance requirement, they just put out so much light if a leaf grows onto it, it'll burn and block the light, too. Fluoros are way better in that regard but at a horrible efficiency. There needs to be some diffusor screen for sidelight LEDs to make them more safe to use.

Side lighting isn't much use in a tent as you are trying to maximise top canopy area as the side lights would be too close to plants but it's perfect for rooms I'd say. You could place them between rows of plants.
In my hut area I can use side lights on 2 sides
For example, 2 x QB288s at 25 watts each you can get ~ 700 umols of light at around 7" away for side lighting.
3 x 2ft F strips at 20 watts each can be placed even closer 3 - 4 inches away. Very efficient lights at that wattage.
I've often thought about diying a suncloack vertical light to drop between the plants but never got round to it..

High wire crops are grown like 10 feet tall with the lights way up high. The bottoms of the plants could easily be 14-16 feet away from the lights.

LEDS in between the rows could be 8 or 10 feet closer to the bottoms of the plants than the overhead lights. In this kind of set up they wouldn't even need to penetrate much to be effective.

key to understanding "penetration" as it relates to indoor grow lights is understanding how light loving plants evolved strategies overtime to maximize photosynthesis under a single intense light source. one way they do this is phototropism, another way is the STACKING of THYLAKOIDS into GRANUM. shade loving plants have short granum, light loving plants (cannabis) have their thylakoids arranged in huge stacks.

to maximize photosynthesis, you have to have enough photons traveling on the same path, hitting the leaf at 90 degrees (which the leaf takes care of thankfully) to fill each thylakoid and move to the next all the way to the bottom of the stack. If you have too many points of light, photosynthesis is only occurring in the top few thylakoids of the grana because there is not enough radiant intensity arriving at the same angle of incidence. This is why there is a point at which adding more lights and running them lower does indeed decrease penetration. However, because you cant replicate the sun indoors, a single point source isn't the answer either. The answer is something in between.

I've tried bringing this up a few times but no one really cares about botany or evidence or sources or anything.

So when we're talking about "Penetration" there's like "Angle of Incidence" where light is coming from many angles. And lower leaves arrange themselves to take advantage of the photons that come in at the right angle. More sources of light increase this effect.

Then there is "Penetration," like the lights blast through the upper leaves and still have enough energy after punching through to get some photosynthesis going down low. I've heard scientists say on Ewe Tube that the green part of the spectrum is what penetrates. And that's why good HPS bulbs and LEDS include so much green, to get that "punch."

I never messed with small, limited spectrum Blurple, UFO style Led lights, but theoretically they should have the least "penetration," right?

seems were back to the usual discussion here, haha.

there is no light really blasting through a leaf.
green is reflected to a good part (why we see plants as green), these green photons are bouncing back n forth and therefore hitting lower areas.
green is also absorbed not only reflected of course but to a lesser degree then other spectra.
And we have far red which seems to really penetrate, but you cant let the plant grow on far red alone.
far red is really facinating.
PPFD level below a leaf are low, always, no matter which spectrum you use or how much you blast them.
when you have 800-1000ppfd on your leaves surface its saturated, few hundred more with CO2 maybe.
then you send your photons from a different angle to hit other area, more diffuse lights
"
Diffuse light penetrates deeper for greater photosynthesis by activating more of the canopy (less shading by upper leaves). In addition, diffuse light helps encourage better growth due to a better distribution of light (more evenly spread rather than with hot spots and shady spots).

In studies on vegetables and pot plants, researchers at the Netherlands’ Wageningen UR Greenhouse Horticulture showed that diffuse light can help provide benefits such as improved crop yield, higher leaf count, lower crop temperature and shorter crop time.

"
.

ive showen spectrometer readings a few times below a leaf, others did before me too, its well demonstrated and good to measure.

cobshopgrow said:

seems were back to the usual discussion here, haha.

there is no light really blasting through a leaf.
green is reflected to a good part (why we see plants as green), these green photons are bouncing back n forth and therefore hitting lower areas.
green is also absorbed not only reflected of course but to a lesser degree then other spectra.
And we have far red which seems to really penetrate, but you cant let the plant grow on far red alone.
far red is really facinating.
PPFD level below a leaf are low, always, no matter which spectrum you use or how much you blast them.
when you have 800-1000ppfd on your leaves surface its saturated, few hundred more with CO2 maybe.
then you send your photons from a different angle to hit other area, more diffuse lights
"
Diffuse light penetrates deeper for greater photosynthesis by activating more of the canopy (less shading by upper leaves). In addition, diffuse light helps encourage better growth due to a better distribution of light (more evenly spread rather than with hot spots and shady spots).

In studies on vegetables and pot plants, researchers at the Netherlands’ Wageningen UR Greenhouse Horticulture showed that diffuse light can help provide benefits such as improved crop yield, higher leaf count, lower crop temperature and shorter crop time.

"

Diffuse Lighting Offers Multiple Benefits

Growers are increasingly learning that steering the greenhouse climate, which includes the related factors of light levels, temperature and humidity, can

www.greenhousegrower.com

.

ive showen spectrometer readings a few times below a leaf, others did before me too, its well demonstrated and good to measure.

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everything you wrote is true but there's many ways to look at this. diffuse light has some benefits but a strong pointy source, too. it is now next to impossible to evaluate which is better or, at what ratio's of diffuse vs direct would be optimal.
a look at nature tells us about +60% of carbon fixed is from direct sunlight (sunplant) and the rest (still much) from sub-canopy light assimilation that consists of green-darkred enriched shadelight and some blueshifted skylight.
I ferl the current ways how industry lamps are designed reflect mostly the ways how to best use the most efficient light emanators in an economic way (ie. no heatsinks anymore to cut costs) and better dispersion.

I don't think the green bounces off all that much, its absorbance is only reduced by a few percentages, maybe 10-15% max in relation to red and blue. Even these 2 aren't fully absorbed (like, only 90%) but since our eyes are much more sensitive to green, we notice that difference discernably.

A good way to study light assimilation is maybe by just looking at a single leaf - esp. since Cannabis has many chloroplasts and can take a boatload of irradiance until light-saturated. The majority of photons are converted into heat etc because the trap/enzymatic processes are slow in comparison to light capture. And this gets worse the higher the ppfd is.
Now some wavelengths are able to reach deeper into the mesophyll and these chloroplasts down there are less agitated, so carbon assimilation will be enhanced if these are reached. This is why green is better at higher ppfd, but not at lower because then the top chloroplasts could still take more - with green being less efficient here.

Another thing to consider is stomatal conductance where esp. UVA can reach deep down and create a blue fluorescence which will open the stomata with benefits to the whole leaf.

Maybe at one point we can have more wavelengths available in efficient monochromatic diodes to maximize these effects?

Kassiopeija said:

...it is now next to impossible to evaluate which is better or, at what ratio's of diffuse vs direct would be optimal...

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Spot on. Pretty much what I was trying to say by the answer being something in between.

For my grow, I try to have 1) completely even par map at the correct intensity, 2) the fewest number of fixtures ran as intensely as possible and as close to the canopy as possible BUT WHICH still achieves a completely even par map at the correct overall intensity. This is the way I feel maximizes overall intensity and radiant intensity at specific angles.

There are inherent contradictions in this that every indoor grow light solves with different priorities, and all the solutions work well and fairly similarly in my opinion.

we can not compare our indoor lightning setups to the sun, sunlight is very even compared to what we consider here as a strong artifical pointy source of light.
you can hold your ppfd meter over your head or lay it on the ground it will show always some similar value outside., sun is huge, simply far far away and do have some quite impressive spread not to forget.

refering to the article posted before, direct light is in advantage when your light levels are low anyway, like in winter.
then the diffusion cost you too much photons.
while this isnt the factor for us, in contrary, using more leds is more energy efficient, giving free photons instead.
.
there is some aplication for every tool.
a pointy lightsource have benefits when hung high and there is a lot roof space above the canopy, you dont want to light.
for the usual smaller tent setups you hardly cant have enough lightsources or spread, most will know the plant will get close to it within no time and you dont want your bud within 2inches of a 50W cob lets say, really not..
basically used every type of led which came out in the last 5 years ( just never bought a overprized blurple) and i have to say my midpower lights have waay more "penetration" then my old CXB3590 setups used.

i have no number at hand how much green is bounced.
youre right that our eye is very sensitvie to green (btw. thats why leds and hps have so much green, theyre not made for plants in first).
i only have the numbers we all know.
think its a bit more then 15%
.
more like 25%, but well, would makes sense to me.
the 25% is what is bounced around or what we see.
i mean, there have to be some green reflected, cleary.


which colors are abosrbed well within the first layers of the leaf and which go deeper i just know from bugbee.
cant watch videos atm, but think its in this
nothing new to you.
is there any ilustration for how UVA behave within the leaf as you mentioned it? @Kassiopeija

this is a eye opening article
"
Background and Aims
Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation.

"

very well funded.

"The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high. "

oh instead of the word penetration we can refer in future to the lambert beer law?
think its a nice name , no one can complain.

"The PPFD decreases exponentially with canopy depth according to the Lambert–Beer law "

for these things are even formulas there.

when we speak of penetration, we should also mention saturation.

"When top leaves were exposed to the full radiation (midday), maximum PSII efficiency (Fv/Fm) was reduced compared with measurements in the morning, suggesting photoinhibition. This reduction was more pronounced in the control than in haze treatments (Fig. 6). "

and i mean, refering to the study which proves us that diffuse light is the way to go.
its not easy to produce light as soft with artifical light as with the sun, as long you dont want to burn your expensvie electric photons in strong diffusion.
such a softbox would give some brilliant light for our plants.

but also would create a lot losses (heat in the end), really a lot.
so the golden middle is to use the direct light of many small leds, my opnion.
the more diffuse the better, but which effort you want to put in for having a few % more is the other question, to each his own but if your setup allows the use of diffuse light (fixture isnt too high causing too much losses on the walls), go for it, its never wrong.

^ the sun is a point source on earth, but the sky provides diffuse light.

I agree with you that adding more lower powered LEDs is beneficial up until the point where you have a very even overall intensity across the canopy. But beyond that, I disagree with any benefit of adding more sources of light and running them at lower intensity. Once you have enough, there is a benefit to what radiant intensity can be preserved by running the individual sources as intensely as possible, and as close to the canopy as possible while retaining even spread. Of course, this is a balance. And I've seen great grows with cobs, strips, pucks, boards, etc. All of them work well if used correctly.