What Umol or PPFD do you run in mid to late flower?

Three Berries

Well-Known Member
I did cut out 2-50ww FS cobs of light this week. 1/3 the total but not the brightest.

I had some hermi once on me back in the day at the end. It always gets me nervous.
 

Milky Weed

Well-Known Member
Great way to put it.

Question for you/the thread - is there a difference in DLI between photos and autos?

I’ve not seen anything address that topic and, at the moment, my 4 Gelatos autos are getting plenty of light. Interesting, though, is that I’m having a hell of a time with a Mg deficiency and falling pH. Could too much light be a factor? Typical approach is to drop TDS until pH stops falling - what about dropping DLI which would/could cause nute uptake to drop which would/could stop pH from dropping?

[hits forehead] Does that make sense? Too high a DLI could cause pH to drop? Don’t mean to hijack the thread but this issue has been plaguing me for a week, including actually losing sleep over it.
I don’t believe there is from my limited research, but I believe in general some people try to run autos harder, nutrient wise atleast. I don’t really know anything about autos I’m sorry. If your having ph issues though, you should definetly post on plant problems and people more experienced than me can help
 

Delps8

Well-Known Member
I don’t believe there is from my limited research, but I believe in general some people try to run autos harder, nutrient wise atleast. I don’t really know anything about autos I’m sorry. If your having ph issues though, you should definetly post on plant problems and people more experienced than me can help
Now that’s an interesting statement = " I believe in general some people try to run autos harder, nutrient wise atleast”.
My impression is that auto growers use lower levels of nutes than people doing photos. :-) I know that I have, though I’ve only done 1 auto grow and 1 photo grow. My current grow is Gelato autos and I just now finished swapping in a res at…145/500 PPM. Yeh, totally weird but I won’t clutter up this thread with my meshugas.

Back to your question about DLI in late flower. I’ve got to read the Chandra paper again. Going back to your question, one thing that I’ve found after using an Apogee for a few months is that I can tell you how much PPFD is falling in a lot of places on my plants but I can’t tell you what my DLI is.
I just took these readings on the plants. There are four plants but the canopy on one (“Jeff") is so much lower I don’t take readings on it.
Looking at the values below, what’s the DLI? The average PPD is 574 and that value is used in the DLI column but, the PPFD down the center averages 631 while the average along the front row is only 527. That’s a range of 100± µmols ≈ a difference of 6 moles for DLI. That’s a lot.
My thinking? Even without CO2 (and we’re at 415 on Manual Loa and much higher in metro areas but I’m not willing to pony up $60 for a C)2 meter :-( ) I don’t think that using the average is a good approach.
One of the drivers for the idea that there’s little value in going over a DLI of 40 is diminishing returns in yield and one of the factors used to arrive at that is electricity cost. I found a site that ran calculations and the cost increase was slight - I should have bookmarked it - vs the increased yield of even a few percent. That’s for a commercial grower. For a personal grower, I’d prioritize the cost difference pretty low because, overall, the cost to run an LED is pretty low.
Right now my light is running 154 watts. If I drop 100 PPFD, my wattage will drop to about 130. Call it a 30 watt drop. Even here in the People’s Republic of California, over the course of a month, the 30 watt delta is just under $5 ( ((30 * 24 * 30)/1000)*0.23) that’s 21.6 kWH at 23¢. I can deal with that. I’m quite happy to I get 5% more weed for $5.
With that in mind, my thinking is to push the DLI higher because LED’s can’t cause direct harm to plants and an increase of N% in light will yield an > N% increase in yield. Eventually, you’ll hit the limits that are discussed in Chandra et al but, as Bugbee says, the biggest issue he sees when called in to look at a grow is that growers are leaving money on the table by not using enough light.

Capto2021-10-30_03-21-05_PM.png
 

Milky Weed

Well-Known Member
Now that’s an interesting statement = " I believe in general some people try to run autos harder, nutrient wise atleast”.
My impression is that auto growers use lower levels of nutes than people doing photos. :-) I know that I have, though I’ve only done 1 auto grow and 1 photo grow. My current grow is Gelato autos and I just now finished swapping in a res at…145/500 PPM. Yeh, totally weird but I won’t clutter up this thread with my meshugas.

Back to your question about DLI in late flower. I’ve got to read the Chandra paper again. Going back to your question, one thing that I’ve found after using an Apogee for a few months is that I can tell you how much PPFD is falling in a lot of places on my plants but I can’t tell you what my DLI is.
I just took these readings on the plants. There are four plants but the canopy on one (“Jeff") is so much lower I don’t take readings on it.
Looking at the values below, what’s the DLI? The average PPD is 574 and that value is used in the DLI column but, the PPFD down the center averages 631 while the average along the front row is only 527. That’s a range of 100± µmols ≈ a difference of 6 moles for DLI. That’s a lot.
My thinking? Even without CO2 (and we’re at 415 on Manual Loa and much higher in metro areas but I’m not willing to pony up $60 for a C)2 meter :-( ) I don’t think that using the average is a good approach.
One of the drivers for the idea that there’s little value in going over a DLI of 40 is diminishing returns in yield and one of the factors used to arrive at that is electricity cost. I found a site that ran calculations and the cost increase was slight - I should have bookmarked it - vs the increased yield of even a few percent. That’s for a commercial grower. For a personal grower, I’d prioritize the cost difference pretty low because, overall, the cost to run an LED is pretty low.
Right now my light is running 154 watts. If I drop 100 PPFD, my wattage will drop to about 130. Call it a 30 watt drop. Even here in the People’s Republic of California, over the course of a month, the 30 watt delta is just under $5 ( ((30 * 24 * 30)/1000)*0.23) that’s 21.6 kWH at 23¢. I can deal with that. I’m quite happy to I get 5% more weed for $5.
With that in mind, my thinking is to push the DLI higher because LED’s can’t cause direct harm to plants and an increase of N% in light will yield an > N% increase in yield. Eventually, you’ll hit the limits that are discussed in Chandra et al but, as Bugbee says, the biggest issue he sees when called in to look at a grow is that growers are leaving money on the table by not using enough light.

View attachment 5019694
Let me help you out with some quick DLI math while I answer the rest of your question.

To get DLI: Take your Umol, Let’s call it 600 for this example.

Take 600 Umol and Times that by 3,600. we do this because there’s 3600 seconds in an hour.

We get 2,160,000. BUT what we then do is convert it to a more manageable decimal.

We turn it into 2.16

Then, take 2.16 x 12 Because we have lights on for 12 hours. if in veg we would do x18.

So our DLI or Daily Light Integral would be 25.92
 

Milky Weed

Well-Known Member
Now that’s an interesting statement = " I believe in general some people try to run autos harder, nutrient wise atleast”.
My impression is that auto growers use lower levels of nutes than people doing photos. :-) I know that I have, though I’ve only done 1 auto grow and 1 photo grow. My current grow is Gelato autos and I just now finished swapping in a res at…145/500 PPM. Yeh, totally weird but I won’t clutter up this thread with my meshugas.

Back to your question about DLI in late flower. I’ve got to read the Chandra paper again. Going back to your question, one thing that I’ve found after using an Apogee for a few months is that I can tell you how much PPFD is falling in a lot of places on my plants but I can’t tell you what my DLI is.
I just took these readings on the plants. There are four plants but the canopy on one (“Jeff") is so much lower I don’t take readings on it.
Looking at the values below, what’s the DLI? The average PPD is 574 and that value is used in the DLI column but, the PPFD down the center averages 631 while the average along the front row is only 527. That’s a range of 100± µmols ≈ a difference of 6 moles for DLI. That’s a lot.
My thinking? Even without CO2 (and we’re at 415 on Manual Loa and much higher in metro areas but I’m not willing to pony up $60 for a C)2 meter :-( ) I don’t think that using the average is a good approach.
One of the drivers for the idea that there’s little value in going over a DLI of 40 is diminishing returns in yield and one of the factors used to arrive at that is electricity cost. I found a site that ran calculations and the cost increase was slight - I should have bookmarked it - vs the increased yield of even a few percent. That’s for a commercial grower. For a personal grower, I’d prioritize the cost difference pretty low because, overall, the cost to run an LED is pretty low.
Right now my light is running 154 watts. If I drop 100 PPFD, my wattage will drop to about 130. Call it a 30 watt drop. Even here in the People’s Republic of California, over the course of a month, the 30 watt delta is just under $5 ( ((30 * 24 * 30)/1000)*0.23) that’s 21.6 kWH at 23¢. I can deal with that. I’m quite happy to I get 5% more weed for $5.
With that in mind, my thinking is to push the DLI higher because LED’s can’t cause direct harm to plants and an increase of N% in light will yield an > N% increase in yield. Eventually, you’ll hit the limits that are discussed in Chandra et al but, as Bugbee says, the biggest issue he sees when called in to look at a grow is that growers are leaving money on the table by not using enough light.

View attachment 5019694
I just wanted to add to the last part of your post, I made this whole thread because I don’t want to light bleach and kill my plants. LED’s are strong enough to harm plants :bigjoint::peace:
 

Troutguide

Active Member
I am running my autos 20/4 at 1000 ppfd. They seem to like 72 DLI but I am running with the same nutes as the photos next door getting 800 PPFD for 12 hrs or about 35 DLI. Bothe rooms have 1500 ppm CO2. And are managed for the lights and VPD.
 

Milky Weed

Well-Known Member
I am running my autos 20/4 at 1000 ppfd. They seem to like 72 DLI but I am running with the same nutes as the photos next door getting 800 PPFD for 12 hrs or about 35 DLI. Bothe rooms have 1500 ppm CO2. And are managed for the lights and VPD.

Yeah thats wild, with Co2 it seems like the sky is the limit
 

Delps8

Well-Known Member
Let me help you out with some quick DLI math while I answer the rest of your question.

To get DLI: Take your Umol, Let’s call it 600 for this example.

Take 600 Umol and Times that by 3,600. we do this because there’s 3600 seconds in an hour.

We get 2,160,000. BUT what we then do is convert it to a more manageable decimal.

We turn it into 2.16

Then, take 2.16 x 12 Because we have lights on for 12 hours. if in veg we would do x18.

So our DLI or Daily Light Integral would be 25.92
Yup, that works for me.
I generally use 0.0036 and then multiply by PPFD µmols and then by hours but there are lots of ways to get there.
 

Delps8

Well-Known Member
I just wanted to add to the last part of your post, I made this whole thread because I don’t want to light bleach and kill my plants. LED’s are strong enough to harm plants :bigjoint::peace:
Oh, I realize that - it's particles impacting plant matter.
One significant factor in > light to get to > yield is heat. Are you able to boost your heat up into the 80's? I have a little heater in hanging from a cross piece in the tent. Nice and toasty in there!
Other factor is RH? Are you using VPD?
 

Apalchen

Well-Known Member
I read a post by mammoth and I’m almost certain it said even with ambient c02 yield rises linear with ppfd up to 1800 ppfd. Now I’m not sure how you would keep plants healthy like that I struggle with c02 and a sealed room if I get much above 1100. I ran 1100–1400 this last run but think my temps were a little high or something as I got more fox tailing than I like. Holding out a few days hoping for one of my slower more fox tailed strains to hopefully finish up a bit more. This was my first run with leds but I’ve noticed some of the strains liked the high temps and led and some didn’t perform as well as in the in the past.
 

Delps8

Well-Known Member
Could this be heat stress? I just moved my driver outside my tent.
My experience has been that excess light causes fox tailing. I ran into it in 2022 at 1250±µmol and once again in my current grow when the dimmer on my grow light failed, setting the light to 100%. One bud was getting > 1300µmol and it ended up fox tailing.

Unlike excess photons, which have a repeatable ability to damage plant tissue, assuming that a plant has an adequate water supply and assuming that VPD is correct, a plant should be able to handle very high temps. At some point, no question, it will be too much but, unless you're in triple digits, I'd suspect that a cannabis plant will do OK at temps where humans would feel discomfort.

At 100°, RH has to have an RH the mid-70's for VPD to be in range but there's very little margin for error. And I'd say forget about terpenes and other goodies at that temp. Mitch Westermoreland did a YT video (Future Cannabis Project) in which he discusses the impact of temperature on secondary metabolites. Excellent video on that topic and on light levels - highly recommended.

1713301472063.png
 

Duckybutt

New Member
Yes i see people pushing 1000ppfd all the time with Co2, maybe next run ill consider it, but this run is without co2. just trying to be careful and thanks for your imput man
I know this is an old thread, but I recently ran 1100-1300 PPFD and pushed to 1400 PPFD.

I pushed to 1400 PPFD in spans of 1-2 hours at a time and then lowered back down to 1200’ish PPFD. Repeated this for the last 2.5 weeks.

I did NOT use CO2. No fox tailing.
 
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