Optimal Light Intensity
"If you want to maximize yield you need to push it hard with light"...Dr. Bugbee Utah State
Whether you grow in a tent or commercial facility, every serious grower should know Dr. Bruce Bugbee’s work on cannabis. From lighting to soil. His plant work is funded by NASA and he has decades of controlled, academic cannabis studies under his supervision.
In his most recent video, Dr Bugbee explains the "higher the number (DLI/PPFD)...the higher the Yield"
We have visited hundreds (maybe thousands) of commercial facilities and we have not observed a single facility hitting DLI/PPFD numbers high enough to maximize yields. Lots of great growers - but yield left "on the table"
The results are shown (both indoor and out) by Dr. Bugbee, Chandra (2009) and our own DLI calculations from Humboldt County.
This study is the progression of the Cannabis growing community - similar to traditional agriculture. A true scientific approach EVERY grower (small to pro) should deploy
There is a false narrative from the largest lighting manufactures on what PPFD/DLI numbers to target - based on their own subjective results and/or lack of light intensity....
Do you know
- HPS will only average 800-1000 ppfd or 40 DLI
- Mammoth can average over 1200 ppfd or 50 DLI
The DLI calculator was created by Agritecture
The #facts point to increasing your light intensity (PPFD), beyond what was previously thought, to increase photosynthesis, growth and yield. 1500 should be the new target and even up to 2000 ppfd.
If you have discussed with the Mammoth team or anyone who grows outside – they will all concur on plant growth under the sun (superior) vs inside. Indoor controlled conditions will still produce higher quality – but the goal is to maximize the plant growth for quicker veg to flower cycles and higher yields.
We will still recommend 1000 ppfd as the target for most growers but if you are a pro grower, using C02 or fresh air – you should target 1500+…
Dr. Bugbee will discuss other factors such as soil medium and nutrients – which we will not opine on.
Every serious grower should also know the Chandra studies (2008 and 2015) which show 1500 ppfd as a target. We will also post shortly or on the website Humboldt county DLI/PPFD numbers (hint…1500ppfd) as well.
HPS vs LED
Most 1000w HPS lights will deliver 500 - 900 ppfd at a 4ft height to the canopy. Mammoth Lights will deliver 900 – 1500 ppfd at recommended heights.
We visit many commercial facilities, using HPS, who hang their lights too high. Many facility lights are >4ft above canopy and their ppfd is <700. The facility plants are healthy but they have lower yields vs potential (plus the additional electrical and heat cost of HPS vs LED)
Your lighting company should provide you with Par Maps at different heights.
Visit www.mammothlighting.com for more information.
From the below 2009 study – “Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions” – as well as the Purdue and US DLI maps, we believe the below guide will help you maximize photosynthesis and thus growth and yield.
To Maximize growth, we suggest ordering an inexpensive Par Meter and/or use this guide:
Bottom threshold for optimal growth and photosynthesis is a DLI of 22:
24/0 schedule: 254.6 micromoles/m2/s-1
18/6 schedule: 339.5 micromoles/m2/s-1
12/12 schedule: 509.25 micromoles/m2/s-1
The Top threshold for optimal growth and photosynthesis is a DLI of 65 moles per day.
***Extremely important notice, only go up to these amounts if you are using supplemental CO2, do not go this high if you are not using supplemental CO2 as you will actually slow down photosynthesis and waste energy.
24/0 schedule: 752.31 micromoles/m2/s-1
18/6 schedule: 1003.08 micromoles/m2/s-1
12/12 schedule: 1504.6 micromoles/m2/s-1
The generally accepted guidelines for artificial light PPFD in flowering during 12/12:
PPFD of at least 510 micromoles/m2/s-1 for the low end of optimal intensity
PPFD of at least 800-1100 micromoles/m2/s-1 for optimal lighting WITHOUT additional CO2.
PPFD of at least 800-1500 micromoles/m2/s-1 for optimal lighting WITH additional CO2.
Use our Par Maps to dial in the correct light height based on the above optimal curve.
Highbay / Greenhouse