LED feed demands

[Guest]

Since I started adding some Epsom in flower a couple times in water I noticed a big diff myself. Plus I also add some BioMin calcium.

 

[voidpainter]

Ok so I’ve been testing a little. Foliar only.

CalMag+ (4-0-0 with Fe, Zn and Mn) doesn’t make much of a difference to be honest. Applied at 2ml / L as recommended on the label. Maybe I should have added more. Maybe I still will. After 3 days there was no visible change.

Epsom does better in my case. I started at 1g / L at start of veg but when the plants got bigger it didn’t cut it anymore. I’ve upped the dosage to 2g / L with immediate results again.

Then I raised the power to 50% at 30cm height (~500 PPFD). The 2g / L epsom wasnt enough to keep up with the vigor. I’m at 3g / L now in order to keep the vigor and no fading on new fan leaves growth.

I spray every 2 or 3 days to keep up with the metabolism.

My temps have also raised from 24 to 28-29C (with 70-75% rH).

More PPFD and higher temps raised the demand for Mg dramatically.

This is crazy.

 

[THC123]

So strangehuh I mean 500ppfd aint that much. My plants under the blurple at 600-700 ppfd are doing fine without adding extra shit. But with these white leds ugh.

And o be honest I don't notice them growing any faster under that white light. I just have way way way more coverage with the same amount of watts under the white led

I can keep em greeen with epsom salts and other additives but still no NORMAL plants. I am now going to change the spectrum a bit to see if I can get em to grow normally again.

 

[eyesdownchronic]

Ok so I’ve been testing a little. Foliar only.

CalMag+ (4-0-0 with Fe, Zn and Mn) doesn’t make much of a difference to be honest. Applied at 2ml / L as recommended on the label. Maybe I should have added more. Maybe I still will. After 3 days there was no visible change.

Epsom does better in my case. I started at 1g / L at start of veg but when the plants got bigger it didn’t cut it anymore. I’ve upped the dosage to 2g / L with immediate results again.

Then I raised the power to 50% at 30cm height (~500 PPFD). The 2g / L epsom wasnt enough to keep up with the vigor. I’m at 3g / L now in order to keep the vigor and no fading on new fan leaves growth.

I spray every 2 or 3 days to keep up with the metabolism.

My temps have also raised from 24 to 28-29C (with 70-75% rH).

More PPFD and higher temps raised the demand for Mg dramatically.

This is crazy.

I have also started messing around with foliar sprays. Allows you to fertilize when you can't water. Thank you for your specificity.

I have been using epsom salts with a mg conc. of 10-15ppm target. Saw very moderate results after two sprays. Then mg def. came back, gave some more mgso4 sprays, but got a Ca def. and had to hook up my dehumidifer (lol)/ tried a CaNO3 spray. Im thinking of making a CaNO3 +MgNO3 spray. We'll see how it goes. Problems really came out for me once the plants got biiigg.

 

[voidpainter]

I have been using epsom salts with a mg conc. of 10-15ppm target. Saw very moderate results after two sprays. Then mg def. came back, gave some more mgso4 sprays, but got a Ca def. and had to hook up my dehumidifer (lol)/ tried a CaNO3 spray. Im thinking of making a CaNO3 +MgNO3 spray. We'll see how it goes. Problems really came out for me once the plants got biiigg.

That’s basically any CalMag product. How come you want to make your own?

Anyway, I think my soil mix doesn’t provide Mg fast enough or it is lacking it completely. I have a heavy Ca and P mix. K for flower I supplement with hardwood ash.

In the future I might consider testing the following:

1) same mix with bigger chunks of pomice / perlite for more aeration. This might address the Mg issue as an airy medium should provide more access to Mg.

2) slightly underwatering as overwatering might make Mg less available.

3) buying a leaf temp. meter. Testing whether 30C / 85F leaf temp makes Mg uptake better due to hard transpiration.

4) adding Kieserite in the soil mix. Kieserite being “magnesium sulfate monohydrate (25% Mg and 50% S). Interested if this will clog the fuck outta the medium tho. Should be tested in a very airy mix to avoid this imo. This would then in theory replace biweekly applications of foliar epsom.

 

[voidpainter]

I’ve done some reading. Looks like the usual white LED spectrum makes the plant put most of the work load on two specific pigments that process the light. These are chlorophyl a & chlorophyl b.

Plants under HID sources and sun use plenty of other pigments to metabolize the spectrum of such light. Others being Carotene, Xanthophyll,
Phaeophytin a, Phaeophytin b.

Chlorophyl a and b are based on Mg, hence the increased demand for Mg as these pigments carry most of the work.

Chlorophyll a absorbs wavelength of 400–450 nm and 650–700 nm

Chlorophyll b 450–500 nm and 600–650 nm.

 

[Horselover Fat]

I’ve done some reading. Looks like the usual white LED spectrum makes the plant put most of the work load on two specific pigments that process the light. These are chlorophyl a & chlorophyl b.

Plants under HID sources and sun use plenty of other pigments to metabolize the spectrum of such light. Others being Carotene, Xanthophyll,
Phaeophytin a, Phaeophytin b.

Chlorophyl a and b are based on Mg, hence the increased demand for Mg as these pigments carry most of the work.

Chlorophyll a absorbs wavelength of 400–450 nm and 650–700 nm

Chlorophyll b 450–500 nm and 600–650 nm.

I don't think this makes sense. You should see much more severe symptoms using blurple if that was true.

 

[THC123]

No because many blurples put out more red and blue and especially red. I do't have any of these issues with blurples.

I bought an infrared thermometer to measure LST.

 

[Horselover Fat]

No because many blurples put out more red and blue and especially red. I do't have any of these issues with blurples.

I bought an infrared thermometer to measure LST.

Still doesn't make sense. White is obviously more spread out spectrum. I think the issue is less IR and thus lower leaf temps or just over all more light.

 

[THC123]

Could be the IR as my burples do emit more ir and heat. But not more light. Reason I say this is that I have a par meter and I have issues at the same par value where they thrive under a blurple or HPS.

Could be light quality?? Maybe 350 par of white light is more difficult to process than 350 par of blurple light? What I noticed is that my SF4000 puts out more blue than red light but so does my vipar. But they differ in the red light being put out.

 

[SuperBadGrower]

What kind of PAR meter is it? IIRC legacy Apogee and Li-cor sensors are already not optimal with red/blue or especially far red, and then there is an even lower tier such as "Hydrofarm".


(Source)


intuitively though, you would expect a discrete diode reading to be lower, rather than higher, using a sub-optimal sensor. Not sure if that is the case in reality.


Maybe cryptochrome is overloaded. Who knows, just looking at lines, always fun. you would expect the same from purple lights because the blue spike is the same wavelength.
Humans also have cryptochromes CRY1 and CRY2. (End baseless conjecture)



Any hydrofarm users don't take it as a jab, I completely get not wanting to spend $500 on a meter. Even after lots of DIY such an expense is not worth it for me

 

[THC123]

I have a hydrofarm as the other ones are too expensive

 

[SuperBadGrower]

For white light it seems to get in the ballpark what I've seen but I would not attach any meaning to its reading under RGB diodes. It may be close but you can never say for sure that the measurement is accurate.

 

[Horselover Fat]

Ok, this is 38 days of 12/12. The plant is under 1236 white 3500k lm301b leds in a 2x4. I run the leds at 320w which should produce about 900ppf or 1150ppfd. My water is 0.1 ec and I add 0.5ec calmag and 1.4ec canna aqua nutes. The lights are about 16-18" from the tops.

 

[mexweed]

I just transplanted and went from t5 to the old original mars 300 blurple, no issues

 

[voidpainter]

@THC123 any info on LST ?

Anyway, I borrowed an IR temp. meter for fun. My environment is currently at 30C, leaf temps are 22C lol. Is this what people usually measure under LEDs?

 

[THC123]

No man still have to measure mine. ALthough that is a LOT of difference, guess it depends a lot on the led.

Btw I am getting healthy plants now by changing the spectrum with added red blue uv and ir

 

[djibra]

i find they eat quite the same but in a less frequent time than under hps for example...

 

[MICrazy]

Another organic, quantum run started. Early flower classic magnesium def symptoms again. Light green chevrons, interveinal chlorosis.



Using reamended soil with 1c/sqft of Dolomite this time. I transplanted a little late and they got root bound (lesson #1,203 learned). They are autos so it is what it is, they look a little small, but first run with this strain so....



Applied a couple epsom foliars and not sure if that is keeping it at bay or doing nothing. Also top dressed with some compost/EWC to rule out nitrogen. Have not drenched yet, not sure I want to.



Lights are fixed to top of tent, probably 3ft away -- running at 100w or about 75%.


After re-reading this thread and a little google-fu, I am going to raise temps to see if that makes a difference. I have a few seedlings that are 3 weeks behind that I can observe for changes/improvements.


Current environment is 78F/55% daytime. 70F/63% nighttime. Going to try and get about 5F more during daytime. Either by bumping power, moving drivers inside tent, adding one more light or a combo of the above. Everything I've seen says run +5-9F.


We shall see.

 

[hyposomniac]

Another organic, quantum run started. Early flower classic magnesium def symptoms again. Light green chevrons, interveinal chlorosis.


Current environment is 78F/55% daytime. 70F/63% nighttime. Going to try and get about 5F more during daytime. Either by bumping power, moving drivers inside tent, adding one more light or a combo of the above. Everything I've seen says run +5-9F.


We shall see.

Your vpd is off.. raising Temps will just make it worse. Instead, keep it 78 but raise your humidity to 65%. Check out a vpd chart..
imho.
Also that's a pretty big dose of dolomitic lime... gotta wonder where your ph ended up - maybe you are seeing iron def?