More light = more yield?
The longer photoperiod got a higher DLI. Also worth noting is that they used a PPFD of only 540 umol/m2s.
Move light = more DLI, no doubt but that's not the issue they were after (interestingly Zheng, a former Bugbee student, collaborated on the attached paper).
To my little history-major-brain, the fact that they didn't control for the increased DLI is a problem. I'm surprised to see what they did. Put aside the meager light level but by changing both the photoperiod and the DLI, I'm not clear on how they can draw conclusions. It looks like a fatal error but I haven't read the paper, start to finish.
Having said that, something's happening here and what it is isn't exactly clear. The DLI change was tiny yet the changes that they recorded in outcome were very significant. If you plough through the attached paper, they're reporting that a 50µmol increase in PPFD about a 5% in crop yield.
This table is based on the information in the Frontiers paper:
The change in DLI is only 1/12 ≈ 8% yet they're seeing significant changes in lotsa other goodies. When you read the Frontiers paper, IIRC, they found no increase in "potency" - just more weed and higher "quality", meaning the ratio of inflorescence to above ground plant mass.
Funny how two similar expirements can appear to come up with different results.
Great to see actual research re. light. I'm a Bugbee acolyte and a believer in "turn it up to 11" when it comes to light levels. Light levels from my current grow, one Glookie in a 2' x 4' tent, day 37.
LR = left rear, RF = right front, etc. Flower light is a Growcraft X3 at 283 watts running 24/0
Column 3 is DLI. 72 is standard deviation of PPFD; 6 is SD of DLI.