Nice to see you back and on the boards, brother.
I keep hearing about people running very low EC and getting good results. When I tried it, I got massive deficiencies.
To the contrary, when I send my EC up as high as 1.9 I get no burn. RH is high, at 75%, temps under control at 80F.
Am I misreading things, I seriously think I see signs of deficiencies at EC 1.3 in bloom!
You're running high RH and it's not fluctuating much I gather. This reduces transpiration.
Think of the plant as a straw. It sucks nutrients up through the roots and moves them to the top of the plant. The rate of transpiration affects the magnitude of the "suction" on the straw.
Higher rate of transpiration = More water/nutrients pulled up into the plant.
Lower rate of transpiration (you) = Less water/nutrients pulled up into the plant.
This is why I recommend fluctuating RH between a min-max value. In nature even during high RH conditions due to the mixing of the atmosphere wind can bring in pockets of lower/higher RH at various times.
So even if there's a period of really swampy RH the plant is still going through this ebb and flow of transpiration. Indoors there is far less fluctuation and so I think you're noticing this effect.
In an idealized model the way I'd think my way around this this is:
1. Feed at high RH (to prevent burning).
2. Drift RH down until you see the beginning of possible overnute.
3. Drift RH up a few points beyond where you saw the burn (2-3%) and call that your new minimum for that particular time in the feeding regimen.
4. As you raise/lower nute levels do this process again and get new minimum value.
As prophylactic measures:
1. If you spot overnute immediately drop temps and raise RH to prevent further damage.2. If you spot nute deficiency, conversely, bring the RH down and increase temps a bit to see if your girl just needs to drink more before actually bumping up the nute in question.
Once you have a feel for what that strain wants fluctuate the RH as follows:
Lights on (RH Maximum) ------> Midday (RH Minimum) ---------> Lights off (RH Maximum) --------> Mid-night (~RH min however close you can get to it) -------> Lights on (RH Maximum)
Something to remember about plants is that they don't really have muscles, so nature has to do most of their work for them.
When we talk about favorability of reactions we think immediately about thermodynamics, from the chemistry perspective.
Something which is very important in thermodynamics is that a system in equilibrium does no work.
In effect what the plant has found a way to make a living on is the IMBALANCE of nature. The idea that RH can be different in one quadrant of the plant versus another (in an instantaneous moment), the fact that temperature changes over the day, all of these imbalances actually provide the source of energy for many of a plants jobs.
If you put your girls in a clean room with perfectly controlled environment some of their systems (like transpiration) will cease almost entirely--because the system will be at equilibrium.
So there are three scenarios here.
1. Perfect equilibrium (full stop on transpiration)
2. The approximation to "perfect" that growers get to (never really truly stop transpiration).
3. Fluctuation.
I'm willing to be yield would order in this list from highest to lowers 3>2>1.
The thing about using a fluctuation, though, is that it does need to be optimized. If you're just being random about it, it could easily end up hurting you more than helping you. The idea is to keep the plant in the conditions it needs
instantaneously rather than approximating a "perfect" value and playing set-it-forget-it.
