Second Grow Problems With Vero Cobs

[StonedGimp]

I’m on my second grow using a Timber 3VL and I’m having the same issues with my plants as last time and maybe you guys can help. The Timber 3VL is 3 Vero 29 cobs/320 watts driver and I’m in a 2’x4’ tent growing in promix soil/perlite using mega crop and other nutes. During both of my grows I’ve experienced severe light burn and stress including bleaching and necrosis spots that look like a magnesium deficiency. I do think using cobs with the mega crop could lead to a magnesium deficiency and the need for extra calmag so during this grow I began using extra calmag and epsom salt. I can now tell, a few weeks later, from shaded leaves the plant doesn’t need anymore and probably has a bit too much if anything but the top and outer leaves are still lightening up and/or beginning to show problems. I tried consistently during the first grow to get the lux level past 24k and never could so I finally stopped there and finished at that lux. During this grow I tried to follow Timber’s instructions but using the light at half power for veg was way too strong when starting out. I eventually made it there at the end of veg beginning of bloom but now at 18” above canopy I can’t get passed 28k this time which is just a little over half. During stretch the plants did shoot up to the light before I could raise it, this was around 36k, and the leaves ended up destroyed in a matter of a few hours. I now have the light at 20” above canopy and would really love to turn it up so the lower buds get some light this time and don’t turn out so fluffy and airy this time. What could the problem be? The temps never get over 85 and I have good air flow. I always check my water ph and now the soil ph everyday.

I’m about ready to give up on the vero cobs and switch to some other led system. I will be adding a second tent, 2’x2’, in the next week and will need a light for that so I’m debating on getting something different for the 2’x4’ and selling the Timber. What would be the best option for lighting a 2’x4’ and if I wanted to add side lighting so below canopy gets some extra light what would be a good option? Any help would be greatly appreciated.

 

[coreywebster]

Is your humidity on point for your temps?

I had this issue when I first got my boards but still not at the lower light levels your using, I tend to struggle in veg if I don't keep vpd reasonable correct and hours of light less.

I haven't used megacrop but I would try a different nutrient before I changed LED , I don't think you will have a different experience with boards.
But I could be wrong, if anything strips would be the option I would go for though but after ruling out the nutrients and environmental variables.

You don't have concrete floors or other reason for cold root zone?
These are photo periods and not autos?
Any lenses on the COBs?

 

[TintEastwood]

Ambient temp 85f is hot. Leaf surface temps? Possibly 90f+.

More common.
75f to 78f.
Low 80s leaf surface temps.

Good to know info...

CO2 Enriched Hydroponic Growing | Manic Botanix

The CO2 fertilizer effect. Article covers contemporary research about yield increases in under lights growing with CO2 enrichment. Optimum ppm and growth.

medteknutrients.com.au

 

[Scuzzman]

have had the same issue many a time- I also grow with Mega Crop V1, pinch of Epsom,1 spray kelp(very weak) maybe Calmag if plants need it,I dont use any other products and grow in 100% CoCo - found if I went over 650 ppm it was worse, also I found moving plants around the grow room helped with the cob hot spots, I now monitor Temp 25 Degrees and RH 55-60% max I dont use Co2 as not needed in my situation... that humidity is a pain as the leaves burn - I do use Sunplus Cobs and Sunplus P6 lights which I'm in the process of changing to HighLight Boards- looking forward to been able to control a few things

 

[Rocket Soul]

I’m on my second grow using a Timber 3VL and I’m having the same issues with my plants as last time and maybe you guys can help. The Timber 3VL is 3 Vero 29 cobs/320 watts driver and I’m in a 2’x4’ tent growing in promix soil/perlite using mega crop and other nutes. During both of my grows I’ve experienced severe light burn and stress including bleaching and necrosis spots that look like a magnesium deficiency. I do think using cobs with the mega crop could lead to a magnesium deficiency and the need for extra calmag so during this grow I began using extra calmag and epsom salt. I can now tell, a few weeks later, from shaded leaves the plant doesn’t need anymore and probably has a bit too much if anything but the top and outer leaves are still lightening up and/or beginning to show problems. I tried consistently during the first grow to get the lux level past 24k and never could so I finally stopped there and finished at that lux. During this grow I tried to follow Timber’s instructions but using the light at half power for veg was way too strong when starting out. I eventually made it there at the end of veg beginning of bloom but now at 18” above canopy I can’t get passed 28k this time which is just a little over half. During stretch the plants did shoot up to the light before I could raise it, this was around 36k, and the leaves ended up destroyed in a matter of a few hours. I now have the light at 20” above canopy and would really love to turn it up so the lower buds get some light this time and don’t turn out so fluffy and airy this time. What could the problem be? The temps never get over 85 and I have good air flow. I always check my water ph and now the soil ph everyday.

I’m about ready to give up on the vero cobs and switch to some other led system. I will be adding a second tent, 2’x2’, in the next week and will need a light for that so I’m debating on getting something different for the 2’x4’ and selling the Timber. What would be the best option for lighting a 2’x4’ and if I wanted to add side lighting so below canopy gets some extra light what would be a good option? Any help would be greatly appreciated.

Does your plants transpire/pray for most of the day? Pics might help a bit. What your talking about is almost allways related to transpiration which is more complicated with leds than other lights. If at 85 youve might have gone a bit to high and stomata is closing on you, especially if your rh is not on point.
Normally these problems come from too cold though. Rec temps are 81-83F. Another thing you can try doing is adding some blue which helps opening stomata.

If you have a healthy plant stance all day i see 2 possibilities:
1 maybe too low ph, i believe mag is easier absorbed around 6.5 than sub 6.
2 you pushed too hard in veg too soon and plants are now somewhat light sensitive. Allways do changes in intensity very slowly, you wanna see healthy new growth before lowering/upping.

Why not try some epson foliar?

 

[SDS_GR]

As a side-note:
The use of Epsom salts ( Magnesium Sulfate ) should be avoided when LEDs are being used as horticultural lighting.
Too much fuss for the LxxBxx numbers going on , while it seems that the biggest enemy* of LED’s service life is being neglected.

* Call me “sulfurization” .

 

[Johnny Lawrence]

As a side-note:
The use of Epsom salts ( Magnesium Sulfate ) should be avoided when LEDs are being used as horticultural lighting.

Why?

 

[Rocket Soul]

Not sure of the exact details but i think the sulfur will deteriorate the phosphor of the leds.

 

[Johnny Lawrence]

Not sure of the exact details but i think the sulfur will deteriorate the phosphor of the leds.

In a hydro setup? Does it like off gas or something?

 

[bk78]

As a side-note:
The use of Epsom salts ( Magnesium Sulfate ) should be avoided when LEDs are being used as horticultural lighting.
Too much fuss for the LxxBxx numbers going on , while it seems that the biggest enemy* of LED’s service life is being neglected.

* Call me “sulfurization” .

LoL

 

[bk78]

Not sure of the exact details but i think the sulfur will deteriorate the phosphor of the leds.

Where can I find this data to read up on?

 

[Rocket Soul]

Where can I find this data to read up on?

I would have to refer to sds on this one. He has a new account but was here much before me and i trust him implicitly, hes an OG of the ledsection from way back when. You can check out sds old account by searching by member: Stardustsailor. Ive never seen someone post so many papers.

I know that lm301h was marketed with a antisulfurization layer but i always thought of it as in burning sulfur against pm.

 

[Rocket Soul]

In a hydro setup? Does it like off gas or something?

I think he meant as foliar. Im not sure

 

[Johnny Lawrence]

I would have to refer to sds on this one. He has a new account but was here much before me and i trust him implicitly, hes an OG of the ledsection from way back when. You can check out sds old account by searching by member: Stardustsailor. Ive never seen someone post so many papers.

I know that lm301h was marketed with a antisulfurization layer but i always thought of it as in burning sulfur against pm.

I get that, but sulfur off gassing through my medium because of the use of magnesium sulfate? Is that even a thing?

 

[Rocket Soul]

I get that, but sulfur off gassing through my medium because of the use of magnesium sulfate? Is that even a thing?

Id think not but i have no idea. I work in a place where we use loads of epson in pools and i havent felt any weird smells which id expect with sulfur so my best guess is no off gassing.

 

[SDS_GR]

https://cdn.samsung.com/led/file/resource/2019/06/Application_Note_Guides_on_Chemical_Compatibility_Rev.0.2.pdf

https://www.vossloh-schwabe.com/fileadmin/user_upload/Chemical_Incompatibility_EN.pdf

https://www.cree.com/led-components/media/documents/XLamp_Chemical_Comp.pdf

https://www.bridgelux.com/sites/default/files/resource_media/AN51_revA%20Chemical%20Compatibility%20of%20Bridgelux%20SMD%20Products.pdf

https://www.nichia.co.jp/specification/products/led/ApplicationNote_SE-AP00012C-E.pdf

https://www.dataweek.co.za/54590n

Chemical compatibility of LEDs – Part 2 - 15 June 2016 - OSRAM Opto Semiconductor SA - Dataweek

The above papers & notes should be enough to read or better yet study...
Not as easy as to laugh out loud ,though...


Magnesium is a very reactive element .
In the case of Epsom salts ,if applied on the soil / hydro tank some of the Magnesium may react with other compounds ,releasing sulfur oxide gas.In the case of foliar feeding some
Magnesium will be absorbed by the plant(s),while sulfur oxides might escape as gas.

Keep in mind that the amount of
sulfur off gassing from an ordinary
small rubber band ,can damage more
than a few LED devices if the ventilation is inadequate.Let alone
from half a spoon of Epsom salts ...

It’ s the internal reflector (made of actual sterling silver ) of the LED die (“chip”) that tarnishes to black,in contact with sulfur in the form of gas( H2S or S oxides ) .
Many of the pc white LEDs that operate at urban environments do lose 30% to 50%
of their output power ,long before
the 50K hour mark ,due to sulfurization.

Just my 2c.
Cheers.

 

[StonedGimp]

Is your humidity on point for your temps?

I had this issue when I first got my boards but still not at the lower light levels your using, I tend to struggle in veg if I don't keep vpd reasonable correct and hours of light less.

I haven't used megacrop but I would try a different nutrient before I changed LED , I don't think you will have a different experience with boards.
But I could be wrong, if anything strips would be the option I would go for though but after ruling out the nutrients and environmental variables.

You don't have concrete floors or other reason for cold root zone?
These are photo periods and not autos?
Any lenses on the COBs?

Vpd is consistently on point for whatever temperature it is in the tent. I basically never leave the room my tents in so I’m constantly turning on/off the humidifier/dehumidifier. The root zone temperature is always about 3-4 degrees Fahrenheit cooler than the canopy. No lenses on the cobs

Ambient temp 85f is hot. Leaf surface temps? Possibly 90f+.

More common.
75f to 78f.
Low 80s leaf surface temps.

Good to know info...

CO2 Enriched Hydroponic Growing | Manic Botanix

The CO2 fertilizer effect. Article covers contemporary research about yield increases in under lights growing with CO2 enrichment. Optimum ppm and growth.

medteknutrients.com.au

The tent only got to 85f maybe 3 times before I changed my filter setup and that reading is from a sensor between my light and the canopy. I have another thermometer that records data always and after checking it I’m pretty sure temperature at the canopy was actually 81-83 during the hottest times. Now even during the hottest part of the day the sensor that always reads warm never gets above 78.5f. I also use a co2 sensor and never really experience a drop below 1000. I was seeing a drop for a few days and I’m pretty sure it was due to the gigantic fan leaves my plants were growing, literally the size of basketballs, so I decided to cut a few off and after that the levels have been fine. I do plan to install co2 after this grow and possibly buy an exhale bag today.

have had the same issue many a time- I also grow with Mega Crop V1, pinch of Epsom,1 spray kelp(very weak) maybe Calmag if plants need it,I dont use any other products and grow in 100% CoCo - found if I went over 650 ppm it was worse, also I found moving plants around the grow room helped with the cob hot spots, I now monitor Temp 25 Degrees and RH 55-60% max I dont use Co2 as not needed in my situation... that humidity is a pain as the leaves burn - I do use Sunplus Cobs and Sunplus P6 lights which I'm in the process of changing to HighLight Boards- looking forward to been able to control a few things

Great to know! After mixing up all my nutes and switching back to well water from half ro/half well I’m at roughly 1060ppm for 2.25 gallons

Does your plants transpire/pray for most of the day? Pics might help a bit. What your talking about is almost allways related to transpiration which is more complicated with leds than other lights. If at 85 youve might have gone a bit to high and stomata is closing on you, especially if your rh is not on point.
Normally these problems come from too cold though. Rec temps are 81-83F. Another thing you can try doing is adding some blue which helps opening stomata.

If you have a healthy plant stance all day i see 2 possibilities:
1 maybe too low ph, i believe mag is easier absorbed around 6.5 than sub 6.
2 you pushed too hard in veg too soon and plants are now somewhat light sensitive. Allways do changes in intensity very slowly, you wanna see healthy new growth before lowering/upping.

Why not try some epson foliar?

I’ll get some pictures today and occasionally when I open my tent the plants are praying. One plant has some leaf curl and I’m pretty sure it’s from running a fan 24/7 that doesn’t oscillate back and forth. I went through 3 oscillating fans last grow and decided this time to use one and set it to not move back and forth. This has saved me time and money but I can definitely tell what leaves on what plants receives air all the time. I not really sure how to fix this problem or what I need to buy/build. Ph has always been 6.5 but maybe I missed something. As for pushing too hard in veg that is a possibility. I tried adjusting the light very slowly throughout veg usually by 1-2k lux every other day and always kept it 18”-20” above canopy except during stretch when everything began to shoot up. I have thought about making a foliar spray and might do that this evening but after reading through everything about the off put of gasses maybe not.

 

[Rocket Soul]

https://cdn.samsung.com/led/file/resource/2019/06/Application_Note_Guides_on_Chemical_Compatibility_Rev.0.2.pdf

Magnesium is a very reactive element .
In the case of Epsom salts ,if applied on the soil / hydro tank some of the Magnesium may react with other compounds ,releasing sulfur oxide gas.In the case of foliar feeding some
Magnesium will be absorbed by the plant ,while sulfur oxides might escape as gas.

Keep in mind that the amount of
sulfur off gassing from an ordinary
small rubber band ,can damage more
than a few LED devices if the ventilation is inadequate.

It’ s the silver internal reflector (made of sterling silver ) that tarnishes to black,in contact with sulfur in the form of gas.

Solution : LED (acrylic) conformal coatings .

But most of the cobs and midpowers have some protection applied to the phosphor right? I know my citizens cobs have some silicon over it.

 

[SDS_GR]

Read the Samsung AN for chemical compatibility more carefully...

Silicone material used as phosphor encapsulants at the
phosphor conversion LED devices is permeable to various gasses.

 

[Rocket Soul]

Vpd is consistently on point for whatever temperature it is in the tent. I basically never leave the room my tents in so I’m constantly turning on/off the humidifier/dehumidifier. The root zone temperature is always about 3-4 degrees Fahrenheit cooler than the canopy. No lenses on the cobs



The tent only got to 85f maybe 3 times before I changed my filter setup and that reading is from a sensor between my light and the canopy. I have another thermometer that records data always and after checking it I’m pretty sure temperature at the canopy was actually 81-83 during the hottest times. Now even during the hottest part of the day the sensor that always reads warm never gets above 78.5f. I also use a co2 sensor and never really experience a drop below 1000. I was seeing a drop for a few days and I’m pretty sure it was due to the gigantic fan leaves my plants were growing, literally the size of basketballs, so I decided to cut a few off and after that the levels have been fine. I do plan to install co2 after this grow and possibly buy an exhale bag today.

Great to know! After mixing up all my nutes and switching back to well water from half ro/half well I’m at roughly 1060ppm for 2.25 gallons

I’ll get some pictures today and occasionally when I open my tent the plants are praying. One plant has some leaf curl and I’m pretty sure it’s from running a fan 24/7 that doesn’t oscillate back and forth. I went through 3 oscillating fans last grow and decided this time to use one and set it to not move back and forth. This has saved me time and money but I can definitely tell what leaves on what plants receives air all the time. I not really sure how to fix this problem or what I need to buy/build. Ph has always been 6.5 but maybe I missed something. As for pushing too hard in veg that is a possibility. I tried adjusting the light very slowly throughout veg usually by 1-2k lux every other day and always kept it 18”-20” above canopy except during stretch when everything began to shoot up. I have thought about making a foliar spray and might do that this evening but after reading through everything about the off put of gasses maybe not.

If you do foliar then cover your cobs (turn them off or way down) and extract a bit before uncovering.
To be able to give high power light you need to have them praying constantly and ph in check for magnesium uptake. You seem to be real close to have it all right.
Another thing is the CO2, it tends to close the stomata, maybe dropping it or check the controls. Or adding some blue/violet/uv which again opens the stomata. Or adding some blue to compensate for lost transpiration due to high co2.
Co2 turned out to be what fucked up our vegg for many cycles, too much of it and no plant breathing.