I found an article on 420greenthumb and it was one of the first DLI papers that walked you through all of the growth stages in regards to lighting requirements (see graphic towards end of post).
For me, after lots of research, it was Shane at Migro who put out the first concise info for DLI and Autoflowers and Photoperiods, where he said all you need is 40 DLI through all phases of growth.
Of course, you need to adjust accordingly if you are running 24 or 20 or 18 hours on.
Shane says 40 DLI is just fine for AutoFlowers and Photoperiods (see graphics below):
For anyone new to this discussion, I won't go into definitions here, but I will give examples:
I'll break it down by the 3 typical light cycles for Autos:
24/0 = 465 PPFD is your minimum for 24 hours lights on if you want 40 DLI. If you want to stay under 50 DLI then your max is 579 PPFD.
20/4 = 556 PPFD is your minimum for 20 hours lights on if you want 40 DLI. If you want to stay under 50 DLI then your max is 695 PPFD.
18/6 = 618 PPFD is your minimum for 18 hours lights on if you want 40 DLI. If you want to stay under 50 DLI then your max is 772 PPFD.
Next, I'll break it down by the 2 typical light cycles for Photoperiods:
18/06 = 618 PPFD is your minimum for 18 hours lights on. If you want to stay under 50 DLI then your max is 772 PPFD.
12/12 = 926 PPFD is your minimum for 12 hours lights on. If you want to stay under 50 DLI then your max is 1158 PPFD.
Now I understand why light companies post PAR results from 12 & 18 inches. For some, getting your lights near 900 - 1000 PPFD you might have to get pretty close to the canopy.
Then you have to balance in that at some point you are wasting energy if you are not running CO2. I think the phrase is diminishing returns.
I'm posting all of this because I have studied the PAR, PPFD, DLI issue for a while and I totally understand it. However, I never truly connected the dots on just what our cannabis plants need to thrive. By all means, if someone has an argument or an alternative view then throw it up here in this post. I just want to make sure all my efforts are maximized. After all, we are talking months out of our lives to get to harvest.
Finally, here's a look at the "piece of an article" that caused this post:
“A farmer is a magician who produces money from the mud.”
― Amit Kalantri, Wealth of Words
@exnavyinstl Hey mate, so as i understand it the DLI is the measurement of photosynthetically active photons delivered to the area in question over a 24hr period. So essentially it gives you a visible point of data for the saturation of photons over the day in a target area, Lighting isnt really my area of expertise but drop bear with me lol. I would take those values you provided above as a guide, albeit a very well researched guide, for your average grower that table is probably perfect for determining your input levels at any stage in the grow however, Plants being plants adapt to their environment and over the course of millions of years have adapted to their specific ecosystem depending on their location on the planet, so for argument sake an equatorial plant would be right at home with larger DLI numbers and would produce better at the higher end of that spectrum, however Autoflowers and northern hemisphere landraces evolved to receive less light saturation due to their ecosystems having much larger variation in DLI. From my understanding, and i have to stress this is just through my own understanding and research of plant biology, you should be able to dial in a specific DLI for the strain your growing to get the most out of that plant while still retaining the plants natural circadian rhythm. This is just how i understand it, I am by no means a bio scientist but makes sense to me.
I am curious though as to how much the DLI would have to do with Phenoic expression, so if the plant is getting the higher end of the DLI spectrum does that mean that it will be more likely to express the more equatorial traits or will it do its thing regardless of that input, i understand that environmental factors play a massive role but would be interested to know if the DLI effects that pheno expression one way or the other. Great Thread mate, you got me thinking!
I feel like a, like a slice of butter... melting on top of a big-ol' pile of flapjacks... yeah.
nice thread ! 
a tonne of great info thank you @ExNavyInSTL
increasing over-all grow efficiency is a whole new ball game since leds got good imo...
A couple of things I would like to add to the above / point out...
1. the DLI for a flowering plants changes through different stages of flowering. To over-simplify you need most in the middle and less at the end when the plant is not in mass-production
2. The perfect DLI is not the same for all cannabis strains. Some plants do well or better from less light, others more (pure equatorial sativa-types for example)
If youre in the stats given above you are dialled with your lighting and running as efficiently as u can... after experience with specific plants some tweaking or not may help
A light meter or the hack shown by shane @migro looks more and more like a v useful bit of kit !
other great sources of light info are Dr Bruce Bugbee, Dr MJ coco and shane @migro of course
thanks again for sharing ExNavy / bubblesH
Time to pop some more beans 😗
Our forum is free to join. We are an international cannabis forum that helps people all over the world grow their own personal supply of cannabis. Through our site you will find cannabis breeding forums, cannabis deficiency forums, indoor cannabis growing forums, and much more.
We are a home growers cannabis forum, and we only allow people who grow cannabis for personal use to be members. Our mission is to help you grow your own cannabis. We do not buy/sell/trade cannabis, or equipment for growing cannabis. Our site is strictly a cannabis smokers forum, cannabis growers forum and forum for medical cannabis users.
Use our guides on how to grow cannabis, cannabis grow diaries, and growers forum to find all the info you need to learn how to grow your own cannabis.
Any member who is suspected of growing cannabis for commercial gains will be banned immediately.
Please read our forum rules, and enjoy the site.
Find us on all social networks! Just search for Percys Grow Room