PPM Inexplicably Rising

Hi everyone,

First time posting, so thank you in advance. I am on my second DWC grow and can’t figure out why the ppm of my nutrient solution is rising. Below is a summary of conditions:

- 2nd week of flower (after estimated 2 weeks of pre flower, 4 weeks after lights were flipped to 12/12)

- My last water change was on 4/13/22 PPM leveled off at 1100 and then began rising to 1230 over the next 5 days.

-Ph settled at 5.8 was relatively stable during this period and no additional ph down or up was added.

- water level also does not change. I have a float valve in the res connected to secondary resovior of plain RO water which is released as the nutrient solution is consumed or evaporates.

As such, one would assume that ppm would drop as the nutrient solution is diluted with RO.

- Ph and ppm are constantly monitored blue lab meter. Solution was rising by 30 ppm per day.

Additionally during this period pistols on some colas began to turn amber (seemed early) and I noticed several fan leaves throughout the plant turning yellow. Location of the dying leaves was not consistent, was more or less throughout the plant. Some tip burn was also noticeable.

I feared my nute solution was too strong and recently dropped the ppm closer to 900 and am not seeing it rise anymore, but am still puzzled by what was causing the ppm to rise given the circumstances. Has anyone else experienced or can explain this phenomenon? What am i missing?

Finally can anyone help me confirm
If this was nute burn or some deficiency driving the discoloration and the early darkening of the pistols. A few photos of what in am seeing attached (lights are off for the night, but I’ll try to post some better images of the discolored fan leaves tomorrow)

I think the strain wants to be purple, at the same time you do have deficiency in some of the lower fan leafs and tips look funky by the buds so you could have a phosphorus deficiency. Ec/ppm fluctuations just mean plant taking more or less water than nuts. If it stayed at 1100 then the plants would be taking equal water and nutrients if I'm not crazy...

That makes sense. I assumed plants consumed the the solution as a whole (both water and nutes equally) I was not aware one could be absorbed faster than the other. Good to know! I will look into the phosphorus. I am using botanicare’s “kind” nutrient system and will add a little more of the solution that contains phosphorus and see if that helps. Thanks for the info!

So that tells you lots tho if you stop and think. If it takes more water than food (ppm rise) that's the opposite of what you want. You want to see the food disappear or at least be kinda equal. It means your ph is off or you fed to strong to fast and the plant didn't like something. Also improper mixing of simple things like ph can lock out large portions of nutrients permanently before it gets to the plant

More is not better. Go back and mix up a ¾ strength feed and check the ppm before you feed. Bet she likes that

Planning to do a full flush tomorrow of ph’d RO water and then taking it easy on the nutes for a bit.

After quickly reading about phosphorous. Do you think this might actually be an excess of phosphorous? She was showing signs of what looked like a mag deficiency in the middle and upper canopy and apparently excess phosphorous can lock mag and other nutes out. I was feeding her pretty heavily leading up to the transition and that continued into pre-flower as she stretched. ppm was dopping by 50-100 per day, but then it suddenly stopped dropping and started rising slightly. That’s when I noticed the leaves and got concerned. Given that, would a build up make more sense than a deficiency?

Also, do you think she can come back from this or is the harvest going to be significantly affected?

Thanks again for the insight. It is much appreciated.

ProPheT 216 said:

I think the strain wants to be purple, at the same time you do have deficiency in some of the lower fan leafs and tips look funky by the buds so you could have a phosphorus deficiency. Ec/ppm fluctuations just mean plant taking more or less water than nuts. If it stayed at 1100 then the plants would be taking equal water and nutrients if I'm not crazy...

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Just figured out how to reply to comments. I don’t want to distract from my most recent question below, but I just realized something about this.

I have a float valve in the res that automatically opens and releases plain RO water into the solution so the water level remains constant. So I’m still confused on how the ppm could be rising if the water she was taking up was being immediately replaced with plain RO water.

The only thing I can think of is hydroguard. Could that be converting some dead plant material into consumable nutrients?

It’s a mute point, since it’s no longer an issue, but the fact I can’t explain what was happening has been driving me crazy.

Are you accounting for your ph adjustments, that adds salts every time, those are numbers we strike off from our actual ec but they are still there

ProPheT 216 said:

Are you accounting for your ph adjustments, that adds salts every time, those are numbers we strike off from our actual ec but they are still there

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ph remained stable between 5.8 and 6. No additional salts were added but ppm still rose.

Fully drain system and refill with proper pH & EC as needed, if PPM get high dilute with water if too high and adjust pH again and again, and again.

He was saying he has a level float so his res always stayes topped of, solution should be dropping in ec with fresh water coming in. Unless you have root rot? I don't know it I am stumped.

In my own system I find that ppm rises when nutrient it too high .

When I have root issue , ph usually drops quickly and more than likely a smell in my tote.

Thanks everyone, roots smell great and look healthy so I’m going to assume the weird rise In ppm was due to a heavy solution. Attached is a photo of the dying leaves in various stages. This morning i flushed added cal mag and ph’d the solution (about 200 ppm) Planning to leave it here for a day or two then slowly increasing back up 700-900 over the next week (Open to suggestions on that strategy/timing) Should I be worried about this substantially impacting my harvest? Overall buds look ok and appear to be fattening. I have about 4 weeks to harvest.

ElFuego said:

Thanks everyone, roots smell great and look healthy so I’m going to assume the weird rise In ppm was due to a heavy solution. Attached is a photo of the dying leaves in various stages. This morning i flushed added cal mag and ph’d the solution (about 200 ppm) Planning to leave it here for a day or two then slowly increasing back up 700-900 over the next week (Open to suggestions on that strategy/timing) Should I be worried about this substantially impacting my harvest? Overall buds look ok and appear to be fattening. I have about 4 weeks to harvest.

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I'm no expert, but I wouldn't wait forever to give them food. Half strength will not be to strong, get them something to live on, and then jump to 700 and see how they respond and go from there. You let all those leafs go light green and yellow playing with starving them your gonna be limping for an extra month to the finish

There's a couple of reasons I've found that makes the ec rise, nutrient too strong or the environment is too dry or/and too hot, your environment plays a major role in plant health, hot/dry conditions causes water to evaporate off the plants leaving the salts behind getting concentrated.

Star Dog said:

There's a couple of reasons I've found that makes the ec rise, nutrient too strong or the environment is too dry or/and too hot, your environment plays a major role in plant health, hot/dry conditions causes water to evaporate off the plants leaving the salts behind getting concentrated.

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are you saying the plant would expel salts back into the nutrient solution?

ElFuego said:

are you saying the plant would expel salts back into the nutrient solution?

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No, what I'm saying is when/if it's hot and dry the plant evaporates more water which in turn raises the ec in the tank ec.

I think that the current popular opinion is that once nutrients are taken up by the plant, they stay there. They can't be "expelled" or "drawn out."

But last week I was watching a video with science dude Harley Smith. Harley talked about a time when EC kept rising in his reservoir. He theorized that the plants released the nutrients back into the water rather than expend energy storing them in the plants.

This kind of flies in the face of forum wisdom, but Harley seems smart enough to trust.

Star Dog said:

No, what I'm saying is when/if it's hot and dry the plant evaporates more water which in turn raises the ec in the tank ec.

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Ahh got it. My system has a float valve connected to a separate RO water tank that keeps it constantly topped off. As such increased water consumption shouldn’t increase the ec as the additional water consumption driven by the evaporation would be immediately replaced with RO water.

youraveragehorticulturist said:

I think that the current popular opinion is that once nutrients are taken up by the plant, they stay there. They can't be "expelled" or "drawn out."

But last week I was watching a video with science dude Harley Smith. Harley talked about a time when EC kept rising in his reservoir. He theorized that the plants released the nutrients back into the water rather than expend energy storing them in the plants.

This kind of flies in the face of forum wisdom, but Harley seems smart enough to trust.

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That’s really interesting.

ElFuego said:

Thanks everyone, roots smell great and look healthy so I’m going to assume the weird rise In ppm was due to a heavy solution. Attached is a photo of the dying leaves in various stages. This morning i flushed added cal mag and ph’d the solution (about 200 ppm) Planning to leave it here for a day or two then slowly increasing back up 700-900 over the next week (Open to suggestions on that strategy/timing) Should I be worried about this substantially impacting my harvest? Overall buds look ok and appear to be fattening. I have about 4 weeks to harvest.

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maybe this can help you diagnose you issue