Quantum Boards burning plants.

unfiltered

Well-Known Member
Just wake up

Heavy ammended soil
Heavy top feed
Why "Heavy"? Is it because you are running QB's at high intensity? Top feed as in top dress or foliar spray? What's in your amendment if you don't mind me asking.

I plan to start amending with a lot Calcium now, not just because of the QB's but because it's required for super healthy growth.
 

boybelue

Well-Known Member
Calcium and magnesium jumped out at me when I seen the pics from the outer leaf margins but it's hard to make an assessment from pics alone. That one plants has a lot going on, looking overwatered but my guess is ph from the burn, droop and marginal issues. Increasing the light just enhances the issue, not that it's to strong, lights are fine, the problem is in the root zone. Imo
 

swedsteven

Well-Known Member
Why "Heavy"? Is it because you are running QB's at high intensity? Top feed as in top dress or foliar spray? What's in your amendment if you don't mind me asking.

I plan to start amending with a lot Calcium now, not just because of the QB's but because it's required for super healthy growth.
 

unfiltered

Well-Known Member
For LEDs 25C and 65 RH falls in the low transpiration zone.
Well, my environment bounces around 25C-27C and 60%-70% RH. When you calculate VPD, do you take into account of leaf surface temperature? When I did my VPD, I also took leaf surface temperature which is very important for proper VPD.
 

charsi420

Active Member
Well, my environment bounces around 25C-27C and 60%-70% RH. When you calculate VPD, do you take into account of leaf surface temperature? When I did my VPD, I also took leaf surface temperature which is very important for proper VPD.
LST would be at least a degree or two cooler, so 60-70 is on the higher side...
 

charsi420

Active Member
Also good luck with measuring LST if using a tent. Surface temp starts dropping as soon you open the tent and start pointing the laser. May get one leaf before the rest have cooled down a bit to get an average reading one can use.
 

unfiltered

Well-Known Member
LST would be at least a degree or two cooler, so 60-70 is on the higher side...
Right. When I first tried to deal with that big plant issue, I had my VPD set optimally. But things sort of got sidetracked to other issues so I kind of left my environment with high RH. I have a couple of younger plants in the flowering tent right now and they are praying though. They seem to like high RH, but maybe transpiration isn't optimal so nutrients are not taken up optimally and thus leaves issue? BUT the plants are praying though which is indicative of very happy plants and the young ones don't have any nutrient issues as of now.
 

unfiltered

Well-Known Member
Also good luck with measuring LST if using a tent. Surface temp starts dropping as soon you open the tent and start pointing the laser. May get one leaf before the rest have cooled down a bit to get an average reading one can use.
haha. Yeh, I noticed that. I usually take the readings really fast when I first open the tent and go with that.
 

charsi420

Active Member
I have a couple of younger plants in the flowering tent right now and they are praying though. They seem to like high RH, but maybe transpiration isn't optimal so nutrients are not taken up optimally and thus leaves issue? BUT the plants are praying though which is indicative of very happy plants and the young ones don't have any nutrient issues as of now.
Because the VPD you're at is suitable for late-veg/early-flower.
 

unfiltered

Well-Known Member
LST would be at least a degree or two cooler, so 60-70 is on the higher side...
I have a VPD calculator from Pulse. https://getpulse.co/blog/vpd#calculate

What's optimal RH for flowering if I run at 25C? Let's say my LST is 22C as the QB's are hung 30" away.

The calculator I have is saying that at 25C and LST of 22C, optimal RH is 48% for kPa of 1.2. kPa 1.2 to 1.6 is recommended for flowering. Is this right? So you are saying I should reduce my RH to around 40% for optimal transpiration?
 

unfiltered

Well-Known Member
I use this link - http://opennlabs.com/vpd/VPD_calculator.php

Yes, you need to lower RH or raise temp.
I have my tent in the non insulated garage and I'm in Canada so it's cold in there. I have a small space heater and 25C is an easy temp to reach. I have to find a way to lower the RH then. But RH of 45% or 40% is super low. I guess the only way to find out is try it.

Thanks! What do you run your environment at during flowering?
 

charsi420

Active Member
I have my tent in the non insulated garage and I'm in Canada so it's cold in there. I have a small space heater and 25C is an easy temp to reach. I have to find a way to lower the RH then. But RH of 45% or 40% is super low. I guess the only way to find out is try it.

Thanks! What do you run your environment at during flowering?
I'm at the other end of the spectrum, need to run the AC 8 out of 12 months. 28-30C, RH I try to keep it around 60.
 
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