[Loopusmagpie2u]

My rooms conditions are spot on with vpd, co2 and feeding regimen. Any time i try to get lights in the optimal ppfd range all my leaf tips turn over and turn yellow on all my new growth. My room is 82* 72%rh 1200 co2. Im growing in soil with nectar for the gods. My soil slurries are 6.5ph and 400ppm. Im in late veg and I cant get lights over 250ppfd. I turned them up to 300ppfd and this is what happens

 

[Blastfact]

What are you using to measure PPFD? I don't see how you can be light burning at a honest 300 PPFD.

 

[freezeland2]

How close is the light and what kind of light?

 

[Loopusmagpie2u]

What are you using to measure PPFD? I don't see how you can be light burning at a honest 300 PPFD.

Apogee ppfd meter

 

[Loopusmagpie2u]

How close is the light and what kind of light?

Lights are 3’ away and its a hlg 550 dimmed down to like 40%

 

[plumsmooth]

That doesn't look horrible and to me it looks like the slight Calcium deificency

 

[plumsmooth]

How old and big are the plants -- are they at least 4-5 weeks old?

 

[Loopusmagpie2u]

That doesn't look horrible and to me it looks like the slight Calcium deificency

No its not horrible right now but it gets worst as it goes on if I dont dim. And the dimmed light kills my yield. The entire line of nectar for the gods is calcium based so im feeding a lot of calcium.

 

[Loopusmagpie2u]

How old and big are the plants -- are they at least 4-5 weeks old?

Yea there pretty old ive topped them a few times because i dont want to flip until there 100% healthy

 

[Chem77]

I don’t during veg, they don’t really like it. I put it to em (100%) by the end of first week or so of 12/12.

 

[Blastfact]

I'm here to tell you. I'm having issues with my Apogee MQ-610 right now. It's been 11% to 14% out against there blue sky calculator for two weeks now. I'm in the middle of email communication with Apogee right now. Looks like I'm going to have to send the POS back for testing and repair. Bought it in March. What a joke....

 

[2Bad]

I don’t during veg, they don’t really like it. I put it to em (100%) by the end of first week or so of 12/12.

Chem has a point. Some plants are finnicky some aren't.

Edit: slowly increase your light everyday . Don't worry about slight tip burn like that. that's not that bad. honestly tip burn is fine as long as the plants look healthy( if caused by light)

 

[Buzzzz]

My rooms conditions are spot on with vpd, co2 and feeding regimen. Any time i try to get lights in the optimal ppfd range all my leaf tips turn over and turn yellow on all my new growth. My room is 82* 72%rh 1200 co2. Im growing in soil with nectar for the gods. My soil slurries are 6.5ph and 400ppm. Im in late veg and I cant get lights over 250ppfd. I turned them up to 300ppfd and this is what happensView attachment 1263036View attachment 1263037View attachment 1263038

Looks like a feeding problem to me,maybe your mix is bad?

 

[2Bad]

You're VPD is off. RH should be 60% with a 80 degree temp.

 

[Peat_Phreak]

Try running 900ppfd with no CO2. This should work if everything else is fine.

 

[Moe.Red]

As you increase light, plant processes increase.

Photosynthesis (assuming you have CO2 and H2O present in sufficient qty 6CO2 + 6H2O → C6H12O6 + 6O2) CO2 yes, H2O good?
Respiration
Other stuff

I think you might be looking at an issue in the root zone that is exacerbated and only shows up with higher respiration.

Also your RH is a bit high making VPD a bit low, meaning the stomata are open but there is so much water in the air that there is not good gas exchange. If you increase the lights, temp goes up meaning RH goes down, VPD goes up, so respiration is restored. In that scenario, if your nutes were out of balance or not enough O2 in root zone, it could look like this and it is not really PPFD doing it, but rather the higher leaf temps and lower RH.

I'm thinking that if your VPD was on point and your watering / nutes / root zone oxygenation was all perfect you could bring that light way up.

It's a friggin balancing act man.

TLDR - I think the problem is actually in the root zone.

 

[Loopusmagpie2u]

As you increase light, plant processes increase.

Photosynthesis (assuming you have CO2 and H2O present in sufficient qty 6CO2 + 6H2O → C6H12O6 + 6O2) CO2 yes, H2O good?
Respiration
Other stuff

I think you might be looking at an issue in the root zone that is exacerbated and only shows up with higher respiration.

Also your RH is a bit high making VPD a bit low, meaning the stomata are open but there is so much water in the air that there is not good gas exchange. If you increase the lights, temp goes up meaning RH goes down, VPD goes up, so respiration is restored. In that scenario, if your nutes were out of balance or not enough O2 in root zone, it could look like this and it is not really PPFD doing it, but rather the higher leaf temps and lower RH.

I'm thinking that if your VPD was on point and your watering / nutes / root zone oxygenation was all perfect you could bring that light way up.

It's a friggin balancing act man.

TLDR - I think the problem is actually in the root zone.

Interesting I was going off this chart pic for environments. Ill lower rh.

 

[ArtfulCodger]

You might try bumping your mag input. Bump 50 ppm each watering until the purple stems clear up. No higher than 500 ppm total. Just an idea.

 

[Neuro]

I wouldn't sweat the purple stems. Very common with LED's and not necessarily a mag deficiency. Given your slurry numbers, pH and the line you're running it's also definitely not a calcium issue. I'm inclined to agree that VPD is probably the issue.

 

[Aqua Man]

VPD is likely wrong because its VPD of the leaf we are concerned with. This will limit nutrient uptake.

The bottleneck to growth is the limiting factor. Which could be many things and everything is relative so improving one leads to a change in other.

VPD is especially important to push those plants with ppfd. To low of a VPD will really set you back and to high is actually less harmful ime.

Read here on the matter.

VPD (vapor pressure deficit)

Ok i was gonna sit down and write out a whole article but i have been lazy so instead instead I'm going to copy paste because im lazy. This is not my work so let start. You may find this very long but its worth the read. Some may want to skip ahead. I have added here and there to what i feel is...

www.thcfarmer.com