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The pea plant (Pisum sativum) was grown in an ebb & flow hydroponics system until it failed; now it's in a deep water culture unit.

I noticed that the leaves were turning brown/grey. I thought this may be a disease so I sprayed Daconcil when needed, but it didn't seem to help. Thinking it might be fertilizer burn, I flushed the system, but now I noticed the leaves are drying up. To rule out the possibility of burning from too much light, I moved the light 2 inches back sideways. However, it's still progressing.

Why is this happening? Here are some details on the setup and environment.

  • Pea Little marvel (Pisum sativum)
  • pH as of now: 6.5 - 6.2 pH
  • Indoors.
  • Light is 100w 6500K (daylight) fluorescent.
  • Light period controlled by timer.
  • Light period was changed from 14 hrs to 16 hrs after light was moved.
  • next to air vent. (always cold)
  • Fertilizer is miracle-gro 20-10-10.
  • water has hydrogen peroxide in it to keep it oxygenated.
  • hydrogen peroxide ratio: 1/4 cup of peroxide per quart of water.
  • Air pump keeps water bubbling/moving to keep it oxygenated (no air stone, just a diy nozzle).

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Here's few more of the same setup: 1, 2 and 3.

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  • Just in case you're not aware, it's best to use the food grade kind of hydrogen peroxide, seeing as they can put stabilizers (not listed in the ingredients) in the regular kind. Stabilizers may include chemicals such as organophosphates (I know that for sure, since I contacted a manufacturer) and I hear heavy metals, too (that, I don't know for sure).
    – Brōtsyorfuzthrāx
    Commented Dec 5, 2014 at 3:23

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  • next to air vent. (always cold)

  • Fertilizer is miracle-gro 20-10-10

Thinking out loud, I wonder if the constant cold air movement could be the problem (or part of the problem)...

That to me seems too strong a fertilizer, unless it's the recommend strength for growing a pea plant in an ebb & flow hydroponics system, is it?

No, but that's all I have. I have stopped using it for a week but saw no improvement

It would take (much) longer than a week before seeing any improvement, if in fact the plant could fully recover from over fertilizing (IMHO).

What is the recommend "general" fertilizer for an ebb & flow hydroponics system?

From my limited knowledge on the subject, it should be well balanced and contain essential micro-nutrients (seeing as there is no soil present).

What about the constant cold air movement, could that have contributed (to the problem)?

The air shouldn't cause a problem because the plant thrives in cool weather, but I think the problem may be the fertilizer.

"Cool weather" & "constant cold air movement" (basically a draft) are two very different things (IMHO).

Regardless of that particular argument, my gut feeling is the imbalanced (and strong) fertilizer is the cause of the problem (for what that's worth).

I recommend looking into specific ebb & flow hydroponics system fertilizers:

  • They're designed specifically for use in such systems.

  • They will contain everything a plant needs to survive, thrive in such a system.

  • They will probably cost more than "regular" fertilizer, but the additional cost should pay for itself in the returns you get from having health plants.

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  • I concur. Too much nitrogen. Not enough potassium. Potassium-deficiency can cause edges of leaves to brown (as can too much nitrogen).
    – Brōtsyorfuzthrāx
    Commented Dec 5, 2014 at 3:44
  • Apparently, not everyone agrees on fertilizer. I've heard one person say that 10-10-10 is fine for plants, and that potassium should never be lower than phosphorus with any plant. No one seems to agree on watermelons, but Monsanto recommends more phosphorus at planting and 17-17-17 for flowering. They probably know more than your average person. I'm not an expert, but I would think a little more nitrogen wouldn't hurt peas, but 20-10-10 seems a disproportionate amount of nitrogen (compared with phosphorus and potassium), unless you're correcting a nitrogen deficiency.
    – Brōtsyorfuzthrāx
    Commented Dec 5, 2014 at 3:55

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