Lighting DLI... What are you running?

[SHRED]

I'm running these autoflowers in the high 50s to mid 60s DLI no problem. 21/3 light schedule.

What's the highest DLI you've ran your crop at with no CO2?

35 days from seed.
Captain Redbeard Big Bud autos.

 

[Bob's Auto's]

First off, beautiful plants you have there.
At those values I would raise the temperature to 27-29°C/80-84°F, get the VPD perfect for that stage of growth and add CO². Anything above 40-45DLI (at it's peak) without all variables at optimum condition and the addition of CO² is a waste of energy...

 

[SHRED]

UPDATE

I adjusted the lights.
Running mid 40s DLI now.

 

[Delps8]

UPDATE

I adjusted the lights.
Running mid 40s DLI now.

No, just no! Not that again.

The chart from growlightmeter.com is not backed by any kind of research. When I tested Photone a couple of years ago, I traded email with the programmer - I've been a software engineer for 30+ years, including 3 for Apple - and he said that they recommend a DLI of 45 because they treat them as if they're always in veg. Oh.

When I asked if there was any research behind that, he referred me to the footnotes on each page.

The bottom line - none, nada, zip.

I've been growing for 2 ½ years now and have done five auto grows and am just starting my second photo grow. In that time, I have spent hundreds of hours learning about grow lighting for cannabis. Chandra, Zheng, Bugbee, etc. I"ve read lots and watched lots of Bugbee vids.

There's no research that has found anything other than crop yield and quality increase when light levels go up and it increases in an almost linear manner.

As light levels increase you have to ensure that the other parts of the grow environment are "co-optimized", as Bugbee refers to it. If they are, cannabis will thrive at 800-1000µmol in ambient CO2.

I regularly run my autos at 900±µmol, using a photoperiod ranging from 20/4 to 18/6. Below is light data from a grow resulted in a very high yield:

Note the comment for 6/8/22 - leading up to that time, I had based my light plan primarily on Bubgee and one or two research papers but I wasn't "turning it up to 11". DeBacco does YT vids but he primarily repackages other research. Even though I knew the numbers by heart, up to that point, I hadn't cranked things up.
That attitude changed that day.
These were autos and one plant came in at 590 gm dry. The smaller one was 139 gm.

Since then, I've found more and more research papers and the song remains the sam - more light, up the light saturation point, yields a larger, better crop.

Of course, you will get a crop at 600µmol. if your environment is good. In fact, in one of the DeBacco vids he says that 600µmols is the least that you should give plants in flower. I agree with that but have seen no research to buttress particular statement - I suspect it was an opinion, rather than an assertion of fact.

I've attached one paper on yield and this table is from that paper. The plants in the study, as with all studies, were not autos but it's all cannabis. Per the table, based on the change in yield that they, a change in PPFD from 600µmol to 900, for example, saw yield increase in an almost linear manner, a la 5.2+4.9+4.7+4.5+4.3+4.1≈29%.

Maybe I can't attach a PDF. :-(

The paper is cited so you should be able to get a copy if that's the case.

Again, no problem with 600µmols; cannabis will survive at 64µmol or higher and up to about 1kµmol. My thinking, based on all available research, is that there's no reason to not feed your plants as much light as they can handle.

This is another auto grow. Similar lighting plan.

 

[Delps8]

If you add CO2, you'll get about a 25% bump, per Bugbee. His recommendation is 1200ppm and 1200µmols. That level of CO2, is confirmed by Fernandez, the guy who wrote HydroBuddy confirms that on his site https://scienceinhydroponics.com. I don't have a direct link, unfortunately, but IIRC, CO2 levels are discussed in one of the blogs that in the blog archive…

[time passes]

https://scienceinhydroponics.com/2021/02/practical-aspects-of-carbon-dioxide-enrichment-in-hydroponics.html

And check out the Chandra paper. It discusses net photosynthesis for different temps and CO2 levels. It's interesting, no doubt, but we're not harvesting net photosynthesis. What was interesting is that, even though the rate of increase in netP rolls off even at 500µmol, yield doesn't.

And, as you state, VPD is key, pretty much the whole enchilada, as I see it, since VPD is what drives transpiration.

 

[SHRED]

No, just no! Not that again.

The chart from growlightmeter.com is not backed by any kind of research. When I tested Photone a couple of years ago, I traded email with the programmer - I've been a software engineer for 30+ years, including 3 for Apple - and he said that they recommend a DLI of 45 because they treat them as if they're always in veg. Oh.

When I asked if there was any research behind that, he referred me to the footnotes on each page.

The bottom line - none, nada, zip.

I've been growing for 2 ½ years now and have done five auto grows and am just starting my second photo grow. In that time, I have spent hundreds of hours learning about grow lighting for cannabis. Chandra, Zheng, Bugbee, etc. I"ve read lots and watched lots of Bugbee vids.

There's no research that has found anything other than crop yield and quality increase when light levels go up and it increases in an almost linear manner.

As light levels increase you have to ensure that the other parts of the grow environment are "co-optimized", as Bugbee refers to it. If they are, cannabis will thrive at 800-1000µmol in ambient CO2.

I regularly run my autos at 900±µmol, using a photoperiod ranging from 20/4 to 18/6. Below is light data from a grow resulted in a very high yield:

View attachment 1651967

Note the comment for 6/8/22 - leading up to that time, I had based my light plan primarily on Bubgee and one or two research papers but I wasn't "turning it up to 11". DeBacco does YT vids but he primarily repackages other research. Even though I knew the numbers by heart, up to that point, I hadn't cranked things up.
That attitude changed that day.
These were autos and one plant came in at 590 gm dry. The smaller one was 139 gm.

Since then, I've found more and more research papers and the song remains the sam - more light, up the light saturation point, yields a larger, better crop.

Of course, you will get a crop at 600µmol. if your environment is good. In fact, in one of the DeBacco vids he says that 600µmols is the least that you should give plants in flower. I agree with that but have seen no research to buttress particular statement - I suspect it was an opinion, rather than an assertion of fact.

I've attached one paper on yield and this table is from that paper. The plants in the study, as with all studies, were not autos but it's all cannabis. Per the table, based on the change in yield that they, a change in PPFD from 600µmol to 900, for example, saw yield increase in an almost linear manner, a la 5.2+4.9+4.7+4.5+4.3+4.1≈29%.

View attachment 1651969

Maybe I can't attach a PDF. :-(

The paper is cited so you should be able to get a copy if that's the case.

Again, no problem with 600µmols; cannabis will survive at 64µmol or higher and up to about 1kµmol. My thinking, based on all available research, is that there's no reason to not feed your plants as much light as they can handle.

This is another auto grow. Similar lighting plan.

View attachment 1651970

Thanks.
I've bumped up the light intensity.

 

[Delps8]

Thanks.
I've bumped up the light intensity.View attachment 1652045

You're welcome, sir.

Great looking plants!

 

[SHRED]

You're welcome, sir.

Great looking plants!

Thanks. About 46 days old.