Study shows 14% increase in tomato yields with interlighting

cobshopgrow

cobshopgrow

Well-Known Member
i would agree that the sky always provide some diffuse light, depending on where you are and season youre in it will differ a lot.

there is no number mentioned sadly.
"A clear, dry atmosphere will produce a large amount of direct light but little diffuse light. You’ll see a high contrast between dark shadows and brightly illuminated surfaces. "
large and little are the max, lol.

i think its still hard to compare a artifical point light source with the sun.
i can go with a spectrometer on a football field and will measure everywhere about the same at noon, if 10m high or at ground.
thats still a freakin even soup of light compared to what we have even using 1000s of leds in a tent.
if flat or round earther, looking at the sun .. better not... it looks like a point and its a source, so yes, point source absolute, but its nothing we can reproduce using tiny artifical point light sources.
 
Last edited:
cobshopgrow

cobshopgrow

Well-Known Member
furbolg said:
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.
Click to expand...
sure there are practical borders and there is a point where the return is very little in comparsion for the effort and money put in.
i can not tell you use x amount of leds and you get x percent more.
could be worth to dig in to the formulas given in the last study and combine it with some own indoor measurements.
but the direction is clearly there and diffuse light is never bad as long it goes in to the direction of your plants, which would be another topic.
people grow in such different sized setups and places, it all have its use.
but even all usual cobs, strips, pucks, boards do work, some do better especially in dense setups (homegrower tents) and those are the ones with the most spread, i clearly can use more height now then with CXB3590, i would fail to grow my stuff if i would need to switch back probably, not even sure if such a bar light would work for me.
 
Horselover fat

Horselover fat

Well-Known Member
cobshopgrow said:
still i think its still hard to compare a artifical point light source with the sun.
if flat or round earther, looking at the sun .. better not... it looks like a point and its a source, so yes, point source why not.
Click to expand...
The sun is 0.5 arc degrees on the sky. It's small. The same apparent size as the moon. You can strech your arm out and still block the moon with your thumb. You could do that with the sun, but like you said: better not try it.

A small soft box, like the one you posted, placed at about a meter from the subject is pretty large compared to the subject and you get quite smooth shadow transitions. At that distance it's much bigger than the sun (uhm, it wouldn't be that hard to calculate, but lets say it's closer to 50 arc degrees than 0.5). Take it ten meters further and it becomes pretty small - probably quite close in size to the sun. At that distance it would be pretty much a point source and create hard shadows on the subject. Actual size doesn't matter, only the apparent/relative size.
 
Kassiopeija

Kassiopeija

Well-Known Member
cobshopgrow said:
is there any ilustration for how UVA behave within the leaf as you mentioned it? @Kassiopeija
Click to expand...
I believe you will find the attached study highly interesting. It shows some benefit of 340nm UVA (increased photosynthesis rates due to (speculated) better stomatal conductance from violet, blue & green fluorescence caused by UVA that transmits much of the upper leaf structure.
 

Attachments

cobshopgrow

cobshopgrow

Well-Known Member
Kassiopeija said:
View attachment 5141982
Sorry to slay you with data. Will read your study now seems highly interesting
Click to expand...
that data is very helpfull to understand, very good study.
havent read it completly but its a very good one for sure.
goes also hand in hand what bugbee is saying and demonstrating with the cross section of the leaf pictures.

" Typical values of absorptance at 550 nm range from 50% in Lactuca sativa (lettuce) to 90% in evergreen broad-leaved trees ( Inada 1976 ). The corresponding absorptance values for blue and red lights range from 80 to 95%."

from your study. for cannabis we need to guess.
 
cobshopgrow

cobshopgrow

Well-Known Member
Kassiopeija said:
I believe you will find the attached study highly interesting. It shows some benefit of 340nm UVA (increased photosynthesis rates due to (speculated) better stomatal conductance from violet, blue & green fluorescence caused by UVA that transmits much of the upper leaf structure.
Click to expand...
this is some very good paper too and the infos of it arent well knowen here.
never sawn this one before.
340nm, yes thats the way it seems, it encourages using more UVA.
i havent read it all now, i am not very clear how long the exposure was and which strenght it had, while i could guess some if comparing to their background ppfd.
 
Kassiopeija

Kassiopeija

Well-Known Member
cobshopgrow said:
thats some good chart, prob most others are scalled to 100% as max while the real world is at least about 7% lower.
goes well in hand with what were talking about here.
Click to expand...
cobshopgrow said:
for cannabis we need to guess
Click to expand...
I'm sorry the data from Beta Test Team isn't correct?

Half a century ago McCree investigated into leaf optical properties of 2-3 dozens of important crop species and found only minimal differences. Like only a few % within dicots. That's was done in preparation of his then famous "McCree curve" that generalizes much but still is a good and confirmed average of many plants' response. I find it unlikely that Cannabis differs greatly here esp. with a multitude of comparative data from other dicots.

From some other works
Leaf transmittance.png
Leaf absorbance.png
Screenshot_20200808-173639~2.png
Leaf reflectance.png
The lightbeam either gets absorbed, transmitts or gets reflected, all 3 incidents mount up to 100%.
If green would just bounce off it wouldn't be able to do much photosynthesis but it does. Plus it has been proven that chlorophylls (the dominant chromophore in leaves) don't reflect these wavelengths, that's due to other compounds.

The science behind it states green gets better the higher the PPFD is and the more the irradiance approaches the light-saturation point. Some green-devoid LED specs show bleaching beyond 1000ppfd

cobshopgrow said:
" Typical values of absorptance at 550 nm range from 50% in Lactuca sativa (lettuce) to 90% in evergreen broad-leaved trees ( Inada 1976 ). The corresponding absorptance values for blue and red lights range from 80 to 95%."
Click to expand...
It's ironic the Samsung study on lettuce + various RBG recipes showed green did better. That's how they got firm on the lm301h-ONE diode. It also works on Cannabis, there are growers (at another forum) using that chip at their quantum board (Bloomstar ONE e.g.) plants look very healthy.

Maybe there are so many incidents within a lettuce-head a lower absorbance makes no difference at? When even farred has a horrible one as compared to green but still Bugbee et al established it's fully metabolised (in a background PAR light situation).

The study in post#26 explains why a less-good absorbance can lead to a higher light assimilation/ photosynthesisrate.
 
cobshopgrow

cobshopgrow

Well-Known Member
Kassiopeija said:
I'm sorry the data from Beta Test Team isn't correct?

Half a century ago McCree investigated into leaf optical properties of 2-3 dozens of important crop species and found only minimal differences. Like only a few % within dicots. That's was done in preparation of his then famous "McCree curve" that generalizes much but still is a good and confirmed average of many plants' response. I find it unlikely that Cannabis differs greatly here esp. with a multitude of comparative data from other dicots.
Click to expand...
i was just refering to that most mccree curves are scaled to a 100% peak, so you can not really guess the real absorbtion.
your chart seems to me better in this.
its just a common scaling issue,

i think no one claimed that green is only reflected and not absorbed, but its clearly more reflected then other colors.
probably like your grafic is showing, a good 20% or something and thats what our eyes probably see.
This reflected green is also what is able to reach lower regions of the canopy, penetration, so at some point it will be used.
every refelction needed is lossy of course.

"absorptance at 550 nm range from 50% in Lactuca sativa (lettuce) to 90% in evergreen broad-leaved trees ( Inada 1976 ). The corresponding absorptance values for blue and red lights range from 80 to 95%. "

idk how to get that in line with mccree, but isnt the study clearly saying it varies by species? lettuce 50%, evergreens 90%, so what will it be for cannabis? am asking myself
and its quite clear that the rates for blue n green are clearly better and more consistent with just 15% variation.
 
Last edited:
cobshopgrow

cobshopgrow

Well-Known Member
tstick

tstick

Well-Known Member
I've said it before....If you want to know the very best spectrum for your plants, then just set up several different types of lights in an empty room....let a cat into the room and wait a few minutes....Come back into the room and take note of which light the cat is lying under. That's the best spectrum!
 
tstick

tstick

Well-Known Member
Probably, but I've seen a lot of recent discussion about how people are starting to go back to the old MH to veg. and HPS to flower -regardless of the efficiency because there seems to be some missing "secret sauce" that the LEDs haven't got in them....So, maybe it's the infra red? In any case, after reading and reading and reading articles on spectral analysis for growing cannabis and watching Bruce Bugby's videos, etc., I think the cat method makes as much sense to me! :)
 
Kassiopeija

Kassiopeija

Well-Known Member
Because Maximum Yield advices no more than 24°C and that with LED LST 21°C which is too cold. Then add more than twice the amount of photons... on "half-frozen" chloroplasts.

When 600w HPS for 4*4 is ~900 umols PPF even less considering horrible spread, reflective light loss and bulb degradation. Why then not pick MH SF etc 2.8umol/J ~= 250w LED for the same canopy PPFD in raw light.

Now this is not ment as "HPS is better than LED" no no no but somehow the raw numbers don't add up but are that which is mainly advertised - "double the light". Then why use 450 watts?
 
You must log in or register to reply here.
Top