Magnesium/iron Issue Coco

[Smellypants]

Hi everyone,

So this seems to be a strange one for me as “apparently” I seem to be the only one with this issue.

So I’ve used canna coco a ton of times now.
Every time I transplant some lovely healthy seedlings/ clones into canna coco, within a week I see what looks to be magnesium/ iron deficiency.

I have tried everything, used house and garden cocos a + b, mills a and b with added Cal-Mag, canna coco a + b with calmag, vegbloom RO/soft, growth tech greenhaze etc.
Before I’ve added plants I have watered until plenty of runoff until I get out what I’m putting in.

I have tried 1.0ec, 1.4ec, 1.8ec and even as high as 2.0ec.
They literally begin to eat themselves after 5-7 days from transplant.

I usually plant, then don’t water for 3 days, then water every other day until they need daily.
Coco doesn’t dry out and I get good dryback between watering.

So on my last run the shop didn’t have any canna (professional plus btw) so I used ecothrive lite.
Not a single problem with the ecothrive at all, actually darkened up pretty quick with the charge it comes with.

So I did a slurry test from a brand new bag of canna.
I took 1 cup of canna coco, 1 cup of 0ppm RO water and mixed it up.
I did not strain the coco before testing as I wanted my ppm meter to detect what the coco itself was holding.
Even after 24 hours of soaking in that water I was only getting a reading of 40ppm.
Now I’ve had some people say that you can’t test the coco’s buffering like that, but in my opinion I really don’t understand how not when the coco is fully saturated.

Now canna told me that their coco is buffered with calmag to an ec of 0.5.

Is it just me or from previous experience and this test I carried out prove it’s not buffered.

I must add, it is not a calcium issue, this is magnesium and possibly iron.

Anyone else have this problem?

I’ve just bought some mills coco with cork and that came back at 300ppm which is what they claim.

One thing I still need to carry out on both products is a runoff test.
This is just to be sure that the mills doesn’t just have 300ppm of sodium which hasn’t been rinsed properly.

Canna has me chasing my tail for the first few weeks, but they do go through a really rough patch of yellowing until they start getting better, then they just take off and look great.

And just so everyone knows my growing methods.

Sealed room
Co2
Cmh or quantum boards
Follow VPD

Using tap water
160ppm
Bump up to 200ppm on 500 scale before adding a + b

I use only the basics, no root boosters, enzymes etc

One thing to note...the yellowing gets far worse when plants are under cmh or quantum boards with co2.
Obviously this is due to them photosynthesising faster.
Under 6k metal halide it isn’t nearly as bad

 

[Seraphine]

What is your pH after you add nutrients?

 

[cemchris]

Most Mg/Fe issues come from lockout from other nutes or PH. Really hard to underfeed on Mg/Fe. Spec with the bottle nutes you listed since most of those have plenty of both (almost everything has mag sulfate in it. If you see a Sulfur % on the label it will most likely have plenty of Mg in it). When it comes to coco that could be feed PH or that could be watering schedule that is causing ph swing/ppm fluc in the medium from being too wet/dry. The other thing is depending on the PH you are feeding and what is actually going on inside the coco as the ph lowers mg will be slightly less available. Why you see soil growers always talking about the meme of more calmg (actually is a meme) but in real life when feeding at 5.5-5.6 strait you actually need to overdose them a little to be fully available. Don't waste your time testing the runoff of coco. That wont really tell you whats going on inside the medium. I've had the best success over they years with feeding Coco @ 5.6-5.7 ph. Spec if treating it like hydro with muti feeds a day vs big pots with multi day dry like soil.

Also some strains are Mg whores the first 2 weeks of flower. More then others. Usually you have to sup them a little hard during transition and if you don't it will show later in the grow.

Usually with A & B nutes you can up the Part A if you need more Ca but not always Mg (dont listen that they need to be mixed at equal ratios. This is to keep their magic ratio on the bottles and feed charts which isn't always ideal ). Sometimes the B has all the Mg in it so you kind of have to know the nutes line pretty well to start going off on your own like that.

 

[MidwestToker]

What temps are you running your room at ?

 

[rickysimples]

What temps are you running your room at ?

This is a good question. I've heard of Ca being difficult for the plant to uptake when the temperatures are too cold, which is common for LED growers.