after reading into VPD and actually seeing the SIGNIFICANT benefits of running 'high' humidity (65-75% in flower) I now truly believe what everyones favorite 'JackMayOffer' was talking about.
i'm not going to get too deep into this conversation and keep it as simple as possible, just as simple as the results i saw from
roughly following the VPD chart were. by roughly, all i mean is that i overpowered my AC in a few rooms and was somewhat
accidentally yielding 2+ a light in a commercial grow with little to no plant training and hardly any effort (aka vegging for 3-4 weeks and topping once or twice)
Overpowering the ACs in my first 'testing' room wasnt was intentional, but the results from growing in a room with 65-75% humidity wasnt. This 'test' room had been neglected and fed inconsistent formulas way off my usual feed chart and I only fed A+B,
calmag, and a PK booster. I was growing in cocobeds DTW... only part was that I didnt drain to waste. I had reused the coco for 3-4 cycles and by the time I decided to flush the beds for once the runoff were reading anywhere from 3000-4000+ PPMs... but somehow hte plants didnt lock out. In my other rooms without proper insulation, the ACs (5 tons for 12 SE bulbs) were struggling because they were running way more often than they were supposed to. The effect of constant AC is that its dehumidifying the air to the range of 40-50%. In those rooms I constantly had thin, purple and stiff plants when I first transplanted up until 2 weeks later when they were large enough to perspire and raise the RH into the 60%s. Those plants wouldnt more often than not lock out if the medium hit around 2500 PPMs and I couldnt understand why even though I was feeding them the full line of nutes from different companies in separate cycles.
Cycle after cycle these rooms that were being babied were always struggling to hit my goal of 2 a light while getting more expensive nutrients and HOURS of training,
trellising and more. The neglected room was effortlessly hitting 2+ a light every damn time with a new roster of strains practically every cycle. Didnt matter if it was a mix of OGs, hybrids, short indicas with 1-2 tables with stunted plants that were didnt even trim and account into the final numbers. We still got 30+ out of a 15 light room.
Finally after over a year and being exposed to the VPD chart I learned why this room was crushing it.