Spectrum - 3000k, 450, 660 and 730 - what to do with the 450 in flowering?

I'm playing a bit with spectrum and I was curious on other's input about what to do once in flowering and ... later in flowering!

Setup is :
3000k (80 CRI) f-strips (10) (samsung)
450 nm (royal blue) 2 strips
660 3 strips
730 3 strips

All strips are on a separate channel so I can play with everything.

What would you use once in flowering and until the end? (it can vary along the way of course)

Would you keep 450nm ON once in flowering? Until the end? At which ratio vs the 3k ?
Which ratio 660/730 would you choose? R:FR / 3000K:R:FR / 3000k/450/660/730? And why?

Does keeping 450nm ON once in flowering delay flowering? More prone to foxtail? hermies? Less yield? Better quality? Lower quality?

Seems the 660-730 is pretty much welcome in flowering vs only f-strip 80cri.

I noticed that, even if pumping the wattage, 450nm doesn't raise PPFD that much, that would be nice to get a spectrometer !

Thanks !

I'd like a light with separate channels that would be ideal.

4/4.5k after flip (depending)
wk4 end 4k lowering to 3k for wk 5 maybe 2.8k, in the last 10/14 days I'd raise the temp to 4k maybe more with some trial and error.

Star Dog said:

I'd like a light with separate channels that would be ideal.

4/4.5k after flip (depending)
wk4 end 4k lowering to 3k for wk 5 maybe 2.8k, in the last 10/14 days I'd raise the temp to 4k maybe more with some trial and error.

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Why raising to 4k last 10/14 days?

Have2 said:

Why raising to 4k last 10/14 days?

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It's only a maybe, it's said a higher k aids trich development at the end.
Some people use mh and 10k finishing bulbs, 10k is maybe a bit extreme for me but if i had the convenience of adjusting the spectrum i might 4/5k, I'd look into it 1st I've only read bits n pieces about it, it might be bs in the real world.

I use 3000k from day one of bloom to the end, if anything I’d like more red, I wish my 3000k quantum boards and strips had reds too. Blue? Nope I wouldn’t want that.. yeah it is said that higher K in the end adds trichs, hard to say how much as I’ve never experienced it, but some people do switch to 10,000k MH at the end so they must do it for a reason right? But maybe only going from 3000k to 4000k wouldn’t be significant enough to matter?

Use the 450 as a transpiration aid. If plants look saggy add some.

I've got both 3k and 4k i use from the start but given the option I'd use the benefits of both but wouldn't be practical to change them, imo there's enough difference between 3k and 4k at the start of the grow to warrant at least trying 4/5k at the end.

Rocket Soul said:

Use the 450 as a transpiration aid. If plants look saggy add some.

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They look perky. But I am wondering what would be the pros/cons of using 450 nm in flowering. 660+ help into promotion of bigger yield but if adding a 450 (royal blue) nm, does it prevent the 660+ to do its job, is it the quantity or the ratio... So much questions and tests to complete!

@Star Dog & @nxsov180db , is it anecdotal or studies have demonstrated the benefits?

As from going to 3000k or 4000K, the difference is minimal and a lot of people seems to think that 3500K is the right answer (3500k+660) between quality and yield.

I'm wondering if adding too much of a specific spectrum could induce foxtail?

I think youd have to experiment with that to work out how it works in your grow really. Hard to give exact instructions.

But some basics: only adding blue to an already balanced spectrum tends to decrease yield and make shorter plants with smaller leaves: blue response. But you could compensate this by adding red and far red.

This is where i would start:
Youd want to add 660 and 730 in good proportions, probably somewhere around 1 part 730, 2-4 parts 660. This is similar proportions to most white spectrum so should work ok i guess. Then figure out how many total watts of red you have. Add 450 in proportion to total red; again use ratios, 1 part blue to 2-4 parts of total red. The ratio of far red to 660 will most likely have an influence on how blues to total reds work out.

Theres also factors like diode efficiency and such its hard to give exact answers. Let your plants guide you. Be careful with high far red input. And too much 450 compared to total reds. But mainly let your plants guide you, theory will always be less important than what you actually see in your grow.

If i could make any change i would replace the 450nm for 400nm, it works similar to 450 but to my experience it increase harvest quality.

Rocket Soul said:

I think youd have to experiment with that to work out how it works in your grow really. Hard to give exact instructions.

But some basics: only adding blue to an already balanced spectrum tends to decrease yield and make shorter plants with smaller leaves: blue response. But you could compensate this by adding red and far red.

This is where i would start:
Youd want to add 660 and 730 in good proportions, probably somewhere around 1 part 730, 2-4 parts 660. This is similar proportions to most white spectrum so should work ok i guess. Then figure out how many total watts of red you have. Add 450 in proportion to total red; again use ratios, 1 part blue to 2-4 parts of total red. The ratio of far red to 660 will most likely have an influence on how blues to total reds work out.

Theres also factors like diode efficiency and such its hard to give exact answers. Let your plants guide you. Be careful with high far red input. And too much 450 compared to total reds. But mainly let your plants guide you, theory will always be less important than what you actually see in your grow.

If i could make any change i would replace the 450nm for 400nm, it works similar to 450 but to my experience it increase harvest quality.

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How much 660 would you add to a 3000k 80 cri strip?

Have2 said:

How much 660 would you add to a 3000k 80 cri strip?

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I dunno, try starting with 10% but still really hard to give generic answers: efficiency per watt is an issue. Also spread: its not the same adding 10% red to a m2 of 400w white by adding 40w bang in the middle as 40w spread over the whole cannopy. Refer to previous answer: let your plants dictate how much they can take, not some dude/Me on a forum. Believe your eyes more than me, i cant see your grow. Also, does it have to be a fixed number already? Cant you just start and try to push it further, back off if you see negative effects etc?
Add more total red than blue, add more 660 than far red. Blue reaction and far red reaction are sorta opposite so keep that in mind, they might offset eachother a bit.

Rocket Soul said:

I dunno, try starting with 10% but still really hard to give generic answers: efficiency per watt is an issue. Also spread: its not the same adding 10% red to a m2 of 400w white by adding 40w bang in the middle as 40w spread over the whole cannopy. Refer to previous answer: let your plants dictate how much they can take, not some dude/Me on a forum. Believe your eyes more than me, i cant see your grow. Also, does it have to be a fixed number already? Cant you just start and try to push it further, back off if you see negative effects etc?
Add more total red than blue, add more 660 than far red. Blue reaction and far red reaction are sorta opposite so keep that in mind, they might offset eachother a bit.

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Currently running the 3K at 720 watts (splitted over 12 strips), 70 watts of RED and 25 watts of FR, everything looks good but I'm not sure I could push the 660/730 higher... Currently at 85% of the driver. So maybe 75-80 watts top without changing the driver.
660 is CREE XP-E2, 730 is CREE XP-E2, 60 diodes of each. I'm not sure I could drive them higher, I'll have to look into it.

As for your input, I just want to hear from other's input/suggestions... I can't think of everything with 100% accuracy so I enjoy the exchanges.

Thank you sir!