The far red thread

[GroErr]

@GroErr
Could you tell us about your setup? Lights used, wattage, distance to canopy and grow space?
I'm asking because it would be good to know which amount of light your plants are getting (DLI).

My guess is that a DLI of ~35 mol/d is what we should be aiming at. 35 mol/d equals a PPFD of around 800 µmols/s*m² at 12/12.
Now the question is, wouldn't it be beneficial to increase the intensity (ppfd) if you run 11/13 for example to keep the DLI at the same level in the hope that you benefit from the significant shorter flowering time but without losing the extra yield you would get whit a longer light cycle?

I don't have a reader but what you're suggesting is on the right track imo. I typically run ~30w/sq. ft. I ran one round on one end of the room with ~22w/sq. ft. one round. It took forever to finish compared to previous runs of the same clone, yielded really well but too long to finish. imo throwing more at them during the shorter cycles would be beneficial. May even shorten the finish further.

Edit: Setup is primarily Tasty Cree 3590's, one 200w bar is Citizen 1212/90cri added more recently. Typically 14-18" above canopy @30w/sq. ft. in ~3.5x8' footprint. Initiators are 35w of 660nm, and 40w of 730nm. Currently running 11.5/12.5.

 

[HideousPenguinBoy]

I didn't have enough controls to get real numbers for weight. My focus with the tests were finish times, secondary was balancing finish time vs. yield.

A great post. So the extra week would have to supply about 11% gain, assuming no lost days between grows/perpetual grow. I'm assuming you would've noticed that much, though.

 

[GroErr]

A great post. So the extra week would have to supply about 11% gain, assuming no lost days between grows/perpetual grow. I'm assuming you would've noticed that much, though.

Cheers, yeah the numbers show that you'd have to see a significant gain by going an extra 7-10 days. The only run I really saw anything that I could credit ~10% gain was running the 22w/sq./ft. config. But that slowed the finish down more like 10+ days with the couple of control phenos I had in there. Just not worth it imo. If yield is a concern, I'd assume that those going for yields would always have sufficient veg space to feed that space perpetually.

What I've been seeing with the current config of COBs with the initiators and lower lights-on cycle is that whatever I throw in there tends to finish a week before they would without initiators and using 12/12. I have further validation as well in a separate tent where I'll run the odd female. When I throw say a 55 day pheno (when run in the main flower room w/intiators) into the 2x2x4' tent with COBs but no initiators, they'll run a week+ longer in there every time.

 

[wietefras]

If it's almost even then what's the benefit of a shorter grow? The hassle of starting up more grows for very marginal gains doesn't sound very appealing to me. I'd rather let the plants go on for a week longer and get some more harvest per round.

Seeing how you didn't keep track of actual yield differences and instead basing it on a guestimate of 10% makes the whole thing rather speculative at best.

From the admittedly few FR experiments I did, I didn't see much difference in grow duration (few days difference at the most) and yield did seem impacted even then.

 

[HideousPenguinBoy]

Seeing how you didn't keep track of actual yield differences and instead basing it on a guestimate of 10% makes the whole thing rather speculative at best.
From the admittedly few FR experiments I did, I didn't see much difference in grow duration (few days difference at the most) and yield did seem impacted even then.

I mean, a 10% increase is pretty noticeable, I would think, but since that wasn't what he was doing with his experiment he didn't get that data. I made a new thread in https://www.rollitup.org/t/light-cycles.956587/ to talk about light cycles/far red sleepy time and such, since this is just supposed to be about reds. I'd love to get some new experiments going.

 

[GroErr]

If it's almost even then what's the benefit of a shorter grow? The hassle of starting up more grows for very marginal gains doesn't sound very appealing to me. I'd rather let the plants go on for a week longer and get some more harvest per round.

Seeing how you didn't keep track of actual yield differences and instead basing it on a guestimate of 10% makes the whole thing rather speculative at best.

From the admittedly few FR experiments I did, I didn't see much difference in grow duration (few days difference at the most) and yield did seem impacted even then.

As I mentioned in one of my posts on the shorter cycle times, that's my preference and was sharing what I found. If I can shave a week off every grow I can grow more variety, particularly when I'm breeding or pheno hunting as it's more about number of plants than weight. I can grow enough weight in one single grow to last me with flower and edibles for the year, I don't sell, so this works better for me. Someone looking for weight may go the other way and let them go longer, whatever fits your style/needs.

 

[Randomblame]

I would say, if you only plan one or two grow's and want as much as possible, then choose the long way.
But for a continuous system, select the faster method so that you can make an extra grow per year.
The usage of far red is more or less user specific and depends on the desired goal.

 

[waynejohn]

For how long after lights out would you run 4 x FR @300ma in an 80x80cm?I'm guessing somewhere around 15min would do the trick

 

[burnpile]

I think its working, 20 min at lights out, 11 - 13 schd. this is 6 weeks 3 days, the sk1 is nearly done, the cryst cndy has some time.

 

[Randomblame]

For how long after lights out would you run 4 x FR @300ma in an 80x80cm?I'm guessing somewhere around 15min would do the trick

2000-4000μMol is enough to switch PhyFr to PhyR and put the ladies into sleepmode.
Do you have four no-name 3w diodes running @300mA?
If yes, you have around 2,3w far-red. Assuming 30% efficiency it would be ~0,7PAR/w. Assuming again the QER is ~3,5μMol/j they would produce ~2,45μMol/s. So to get 2000μMol it needs 816seconds or 13,5 minutes and for 4000μMol you need twice as much time.

Ususally my girls get the first half of the light before the main light switch off and the second half while the mainlight is off. If you use better LED's like Cree or Osram top bins you can shorten the far-red cycle to 10-20 minutes.
BTW,
The 3.5μMol/J QER are cherry picked from the Luminus LED calculator and I just assume that all 730nm diodes are in this range. Cree/Osram top bins @300mA should reach around 42-43% efficiency.

 

[waynejohn]

I have cree -00701, so i should be good with runing them 15min before and 15min after to keep it simple and still be in the safe zone concerning stretching?Does the stretch trigger immediately after you pass the 4000 micromole mark or do you have some headroom before it activates stretch?

 

[Randomblame]

If they stretch you will see it within a few days. Most strains responds a bit differently.

 

[alesh]

2000-4000μMol is enough to switch PhyFr to PhyR and put the ladies into sleepmode.
Do you have four no-name 3w diodes running @300mA?
If yes, you have around 2,3w far-red. Assuming 30% efficiency it would be ~0,7PAR/w. Assuming again the QER is ~3,5μMol/j they would produce ~2,45μMol/s. So to get 2000μMol it needs 816seconds or 13,5 minutes and for 4000μMol you need twice as much time.

Ususally my girls get the first half of the light before the main light switch off and the second half while the mainlight is off. If you use better LED's like Cree or Osram top bins you can shorten the far-red cycle to 10-20 minutes.
BTW,
The 3.5μMol/J QER are cherry picked from the Luminus LED calculator and I just assume that all 730nm diodes are in this range. Cree/Osram top bins @300mA should reach around 42-43% efficiency.

QER of a far red LED (peak wavelength 730 nm) should be around 6 µmol/J.

 

[Randomblame]

QER of a far red LED (peak wavelength 730 nm) should be around 6 µmol/J.

Really 6μMol/J?
Can you say why?
The best deepreds have ~5,5μMol/j and above 700nm light contributes much less to photosyntesis. Far red is mostly used by phytocromes and for signaling as well as for shade avoiding. It's also used by the emerson effect and boosts photosyntesis but I can not believe so much that it results in 6μMol/J. As I said, I got the numbers from Luminus calculator, sun plus series and 3,5μMol/J makes much more sense to me.
But I'm always ready to learn something new and maybe the guys from Luminus are simlpy wrong ..? It would not be the first time someone here proves that official metrics do not apply.

 

[wietefras]

@Randomblame, Yes, I digitzed the SPD for my Osram SSL 730 leds a while ago and also arrived at a QER of 6 umol/J.

 

[Randomblame]

@Randomblame, Yes, I digitzed the SPD for my Osram SSL 730 leds a while ago and also arrived at a QER of 6 umol/J.

Okay, thank you for agreeing!
Then I will also calculate with 6 in the future, which is actually a good thing, LOL, because I need in future much fewer diodes to produce the desired amount far-red.

 

[wietefras]

Osram quoted 36% efficiency in their 2015 datasheet (when I got them). So I guess then you'd get 2.16umol/s/W overall (watts from the wall). That sounds reasonable. Probably better nowadays.

 

[alesh]

Really 6μMol/J?
Can you say why?
The best deepreds have ~5,5μMol/j and above 700nm light contributes much less to photosyntesis. Far red is mostly used by phytocromes and for signaling as well as for shade avoiding. It's also used by the emerson effect and boosts photosyntesis but I can not believe so much that it results in 6μMol/J. As I said, I got the numbers from Luminus calculator, sun plus series and 3,5μMol/J makes much more sense to me.
But I'm always ready to learn something new and maybe the guys from Luminus are simlpy wrong ..? It would not be the first time someone here proves that official metrics do not apply.

This "QER" value has nothing to do with photosynthesis, photomorphology or the Emerson effect.
It's just a measure of how many micromoles of photons of this spectrum are equal to 1 joule of photons of this spectrum. Higher wavelength means higher QER.
The fact that these photons might be less useful is another story.

Would you happen to have a link to the calculator?

 

[Randomblame]

Here it is, but it's LumiLED's not Luminus..., sorry!

https://www.lumileds.com/horticulture/calculator/

 

[giantsfan24]

So my setup is 2x2x4 with a 210w, they said 200w but the kill a/w says different, Timber grow light citizen clu48, 3500k.

Should I add red? If I should, what does anyone recommend? Lol sorry to be lazy, this is a long thread.