Olderfart back for advice again - Iron deficiency?

[Waira]

Thanks for the feedback everybody, I appreciate it.

@Waira , my runoff has been high, and when I measured it, pretty much the same pH as going in, and lower EC. But I will check it this morning and get back to you, it has been a while since I bothered. I will check it on a couple of the other larger plants too to see if this has gotten away from me since I checked last. I have been assuming that my excess runoff would take care of any buildup or balance issue (I suspect a fair bit more than 20%).

Ahhh, but the plant's nute uptake rate does change, big time in fact at this stage... And that seems to be what happened since your previous measurements were looking okay thanks to that 20% run-off! My coco-guru-nuts would likely advise 25-30% with ppm's that high...
It's all too easy to get caught in this jam mate, coco is little distanced from full-on hydro, and we know that shite can go sideways faster in hydro than any other method of growing. Case-in-point: look at the nute availability chart for hydro, and note just how narrow a band of "optimal" pH there is; if it drifts just a couple-few tenths, and the potential for hiccups is right there...... coco's behavior leans far more to the hydro side than it does the true soil side...
High quality nutes with truly great chelation can help protect those certain nutes from undergoing chemical form changes that prevent uptake, but even that can only go so far,... That said, pH charts are a guide line, not the bottom line! there are other factors that offer wiggle room, or not, and make things muddy up to the point that it's hard to tell what's cause vs. downstream effect = *( now you know why I "retired" from Sick Bay duty, to save my sanity!)

Well peeps, the puzzle may be solved. When I checked runoff this morning, pH in runoff from two of the large pots was ~4.2. That would be four point bloody two! I had monitored pH and EC in runoff for a couple weeks earlier on, and it seemed that the only pH issue was that the reservoir would drift upward gradually for a couple days, so I would start it at ~5.8 and let it climb after that. That usually meant that it would stabilize in range (5.8-6.2). None of my runoff was significantly different than input, so I backed of monitoring the runoff. Since I fertigate to more than 20% runoff, I figured that little mischief in the medium was likely. Seems that I was wrong.

C'est bon mon amie! .... that certainly explains it, and with that pH, we can rule out Fe since even really low pH doesn't cause lockout in it; it's high pH that is Fe's nemesis, even 7.0 may start it! Now, it's S (SO4--) than hates low pH, and S defc. does usually show in even overall fading,...Fe not so much...
The high r-o ppm's didn't help either though-
That's the hitch mate, from what I saw in ER here, seldom was it so simple as a basic lack of defc.,... usually it was a combo of things that build the shit-show!

Truth be told OF, I've not used pure coco but once... I had to learn the bumps just the same though working in here! Coco is NOT an easy medium to run, not very forgiving and often an SOB to correct. It's bitchy CEC and Ca/Mg juggling act are an added challenge on top of everything else vs. soilless peat based medium.
I have heard of coco doing some odd pH drifting, down and up (especially weird)... So many things, chemical and biological effect pH that it's hard to say what's the culprit with that.
You mentioned your lovely low ppm water! Recall, the softer the water is, the less pH buffering capacity it has. Also very important to know: it's the carbonate part of CaCO3 that's doing the buffering, the CO3-- anion becoming bicarbonate HCO3- and thus taking an [H]+ out of the equation....
A Ca-Mg product may or may not have a carbonate formulation, many go the nitrate way instead, and that don't help none 'tall! So, if you're adding Ca-Mg, you still may not be getting enough carbonate going in to really help with the wild pH swings that low ppm water displays...
Assess your carbonate inputs, maybe that is in part at least a cause for the pH drifting....
Otherwise, you've done what you can with the reset - .. it's not that bad at all, and shouldn't be much of an issue for performance/quality unless it goes absolutely sideways,...and it ain't!

 

[DCLXVI]

Man-O-Green explained to me that the plant shoots out a lot of different compounds when it "wants" something. Especially at flowering. I've had my runoff pH drop a ton and it's just the plant doing it's thing through the roots. Waira made a lot of good points especially about the hydro vs coco. There is a point when the flowering transition happens that can trigger a significant drop in pH. I had it in one of my early coco solo cup experiments. Can't fight it. Just keep the inputs going where they need to be. You can sort of "flush" through it or just run a bit more runoff volume.

I do think keeping an eye on runoff EC/ppm is not a bad idea. You can track trends and know if you should push or pull on the strength. A decent guideline is to try and stay within 300ppm over input.

What's your current nute blend in g/gallon? I've had better luck bumping the epsom a bit more than the Jacks chart suggests. That will also add Sulfur. (1.3g/gallon instead of 1.1)

The part B should be plenty of Ca on it's own.

Are you adding anything else beyond the 3 part Jacks formula? I add silica as a pH buffer and it brings it up nicely as the Jacks is quite acidic on it's own. Stable pH for several days too. Might be worth looking into if you are going to continue Jacks/coco.

 

[idiopathic neuropathy]

Coco grower here---I have often measured ec and ph runoff. I have experienced low 4's ph and the plants have shown no ill effects. At first, i would flush to get the pot in the 5.8-6.2 range and within a short period of time it would drift back down. After doing some internet digging on the subject, there are articles out there that state that ph runoff testing is rather worthless for cocc--so I have given up on ph testing, but still test for ec.

 

[Olderfart]

Man-O-Green explained to me that the plant shoots out a lot of different compounds when it "wants" something. Especially at flowering. I've had my runoff pH drop a ton and it's just the plant doing it's thing through the roots. Waira made a lot of good points especially about the hydro vs coco. There is a point when the flowering transition happens that can trigger a significant drop in pH. I had it in one of my early coco solo cup experiments. Can't fight it. Just keep the inputs going where they need to be. You can sort of "flush" through it or just run a bit more runoff volume.

I do think keeping an eye on runoff EC/ppm is not a bad idea. You can track trends and know if you should push or pull on the strength. A decent guideline is to try and stay within 300ppm over input.

What's your current nute blend in g/gallon? I've had better luck bumping the epsom a bit more than the Jacks chart suggests. That will also add Sulfur. (1.3g/gallon instead of 1.1)

The part B should be plenty of Ca on it's own.

Are you adding anything else beyond the 3 part Jacks formula? I add silica as a pH buffer and it brings it up nicely as the Jacks is quite acidic on it's own. Stable pH for several days too. Might be worth looking into if you are going to continue Jacks/coco.

I am using silica, and when on Bloom, I add a bit of cal mag. The single part formulations seem a bit low in Mg and maybe Ca to me. When on 321, the epsoms ratio is increased ~10% compared to the regular Jack's ratios (don't quote me on the exact percent, it is whatever Kootmed's most recent coco schedule is, so it is already tuned for coco).

It will be interesting to see whether my overhaul yesterday keeps things on track.

 

[Olderfart]

Coco grower here---I have often measured ec and ph runoff. I have experienced low 4's ph and the plants have shown no ill effects. At first, i would flush to get the pot in the 5.8-6.2 range and within a short period of time it would drift back down. After doing some internet digging on the subject, there are articles out there that state that ph runoff testing is rather worthless for cocc--so I have given up on ph testing, but still test for ec.

I would not bother if there were no worsening symptoms, but since there are, I did the correction. It will be interesting to see what happens, including trends in runoff pH. I may just end up repeating your experience.

 

[Olderfart]

Ahhh, but the plant's nute uptake rate does change, big time in fact at this stage... And that seems to be what happened since your previous measurements were looking okay thanks to that 20% run-off! My coco-guru-nuts would likely advise 25-30% with ppm's that high...
It's all too easy to get caught in this jam mate, coco is little distanced from full-on hydro, and we know that shite can go sideways faster in hydro than any other method of growing. Case-in-point: look at the nute availability chart for hydro, and note just how narrow a band of "optimal" pH there is; if it drifts just a couple-few tenths, and the potential for hiccups is right there...... coco's behavior leans far more to the hydro side than it does the true soil side...
High quality nutes with truly great chelation can help protect those certain nutes from undergoing chemical form changes that prevent uptake, but even that can only go so far,... That said, pH charts are a guide line, not the bottom line! there are other factors that offer wiggle room, or not, and make things muddy up to the point that it's hard to tell what's cause vs. downstream effect = *( now you know why I "retired" from Sick Bay duty, to save my sanity!)


C'est bon mon amie! .... that certainly explains it, and with that pH, we can rule out Fe since even really low pH doesn't cause lockout in it; it's high pH that is Fe's nemesis, even 7.0 may start it! Now, it's S (SO4--) than hates low pH, and S defc. does usually show in even overall fading,...Fe not so much...
The high r-o ppm's didn't help either though-
That's the hitch mate, from what I saw in ER here, seldom was it so simple as a basic lack of defc.,... usually it was a combo of things that build the shit-show!

Truth be told OF, I've not used pure coco but once... I had to learn the bumps just the same though working in here! Coco is NOT an easy medium to run, not very forgiving and often an SOB to correct. It's bitchy CEC and Ca/Mg juggling act are an added challenge on top of everything else vs. soilless peat based medium.
I have heard of coco doing some odd pH drifting, down and up (especially weird)... So many things, chemical and biological effect pH that it's hard to say what's the culprit with that.
You mentioned your lovely low ppm water! Recall, the softer the water is, the less pH buffering capacity it has. Also very important to know: it's the carbonate part of CaCO3 that's doing the buffering, the CO3-- anion becoming bicarbonate HCO3- and thus taking an [H]+ out of the equation....
A Ca-Mg product may or may not have a carbonate formulation, many go the nitrate way instead, and that don't help none 'tall! So, if you're adding Ca-Mg, you still may not be getting enough carbonate going in to really help with the wild pH swings that low ppm water displays...
Assess your carbonate inputs, maybe that is in part at least a cause for the pH drifting....
Otherwise, you've done what you can with the reset - .. it's not that bad at all, and shouldn't be much of an issue for performance/quality unless it goes absolutely sideways,...and it ain't!

Thanks for getting back @Waira. Your point about carbonate may be important. Adding some of my tap water to the mix might help with that, which I will keep in mind while I see how things go.

 

[Olderfart]

Man-O-Green explained to me that the plant shoots out a lot of different compounds when it "wants" something. Especially at flowering. I've had my runoff pH drop a ton and it's just the plant doing it's thing through the roots. Waira made a lot of good points especially about the hydro vs coco. There is a point when the flowering transition happens that can trigger a significant drop in pH. I had it in one of my early coco solo cup experiments. Can't fight it. Just keep the inputs going where they need to be. You can sort of "flush" through it or just run a bit more runoff volume.

I do think keeping an eye on runoff EC/ppm is not a bad idea. You can track trends and know if you should push or pull on the strength. A decent guideline is to try and stay within 300ppm over input.

What's your current nute blend in g/gallon? I've had better luck bumping the epsom a bit more than the Jacks chart suggests. That will also add Sulfur. (1.3g/gallon instead of 1.1)

The part B should be plenty of Ca on it's own.

Are you adding anything else beyond the 3 part Jacks formula? I add silica as a pH buffer and it brings it up nicely as the Jacks is quite acidic on it's own. Stable pH for several days too. Might be worth looking into if you are going to continue Jacks/coco.

I forgot to answer your question about g/gallon. I don't manage it that way, I mix a batch up which targets a final EC stronger than what I want, and I then dilute to the EC I want to operate at. The ratio of A, B, And Epsoms is what Kootmed's most recent schedule for coco lists. I have no idea what my g/gallon ratio ends up at.

With 321, I mix up stock solutions at 100x, so nutes are already fully dissolved, and mixing a batch is reasonably quick.